Experimenting with Saltwater Verticals & Phased Arrays
7 Mhz Portable & Fixed-Phased Operation Along the Atlantic Seaboard • Beverage Receiving Antennas
~ WELCOME ~
Here's what we ended up with.
East and West Verticals of the 7 Mhz Phased Array • Construction Time: 4 Months
Each vertical is elevated 4 meters above ground, and outfitted with 30 counterpoise wires. • The Christman phasing method is employed. • The 60 counterpoise wires are suspended from a catenary line strung around both verticals.
Scrolling down this page provides technical information about this and additional 40 Meter antenna projects--and the latest updates.
Hahah! Bill, your Zed page is awesome
Dr. Nathan "Chip" Cohen, W1YW
Vice President, Radio Club of America
Astrophysicist, Inventor of Fractal Antennas
I found your QRZ page more enlightening than any of the ON4UN and ARRL antenna books. Thanks for that.
Rick Ciotti, W3DIY
I really enjoy your engaging style of writing and the way you make the reader feel your pain, elation but mostly your undaunted enthusiasm as you take us with you on your journey towards the ideal vertical array.
Brian Roberts, G4DBQ
Just going thru your QRZ page -- absolutely awesome!!!
Geoff Dobson, G8OFQ
Your page is wonderful. I'm really impressed.
Derek Fichter, HL1ZIX
Your qrz page is a gold mine, and I will be studying it.
Al Brenner, W4ALO
UPDATE: March 13 - 20, 2017
2-WIRE AFRICA-PACIFIC BEVERAGE for 7 Mhz
Converting the 290' Western Beverage into a 2-wire reversible affair • Aerial now operational • Scroll to bottom of page for details
Beverage & Support Posts
Tuning the Differential and Common-mode Feedpoint Transformers Prior to Field Installation
Differential and Common-mode ports, seen in the scope traces above, tap East & West reception signals off the 2-wire Beverage
$1 transformers balanced to minimize crosstalk
Feedpoint & Reflection Transformers Housed in Weatherproof Boxes
Feedpoint & Reflection Transformers
Feedpoint and Reflection transformers mounted to wooden stakes during tuning stage
Feedpoint & Reflection End Insulators
Made of 1/2" PVC tubing reenforced with fiberglass rods
2-wire Beverage Spreaders
Made of fiberglass snowplow markers • $6 for six 48" rods • Cut to 3" • Holes spaced 1" apart
Support Post & Partial Beverage Span
1/2" PVC tube inserted into end cap embedded in one end of black 2x4 • Crossarm is fiberglass snowplow marker painted black
UPDATE: March 7, 2017
SB-220 ALC MODIFICATION
Variable ALC for legacy amplifiers -- modernized for solid-state rigs -- enhances "Talk-Power" while reducing IMD splatter • Details appear at the bottom of this page
SB-220 Equipped with PTT/ALC Connector & Variable ALC Threshold Control
Prototyped by W1ZY & WA5AVK. • Commercial kits in development. • Details to shortly appear at the bottom of this page.
UPDATE: February 7, 2017
RESTORATION OF HALLICRAFTERS S40-A RECEIVER
Learn how to recondition this classic 1940's receiver • Details appear at the bottom of this page
Photos & details at the bottom of this page.
"I saw your very nice restoration on QRZ.com. I was given a S40 along with a S-meter. I have shipped the S-meter to you. I thought it would be a good addition to your restoration !!!"
OUR STORY BEGINS HERE
• The Saltwater Vertical Experiment •
The Saltwater Vertical Experiment began in January, 2016, with the objective of learning as much as possible about vertical antennas on the 40 Meter band. This endeavor was triggered in December, 2015, by working Asian stations longpath from a car parked next to the ocean with the assistance of Canadian ham radio operators. Since then, this "biography" page has been commandeered to record the adventures, insights and tips garnered by constructing, tuning and operating several vertical antennas on 40 Meters. The material is presented in chronological order, which means the most recent developments are at the bottom of this page, in support of a book about this fascinating topic.
The construction methodology is the same used by original wireless amateurs--when parts cannot be scrounged, they are purchased from local suppliers. Which in the modern day means most of the parts needed to build the antennas can be had at Home Depot. Over the course of the year our experimental antennas went from this, to this, to this.
Evolution of Antenna Experiments Over 1-Year Period
The Saltwater Vertical Experiment has three phases
PHASE I: Inductively-loaded Portable Vertical • January, 2016
Inductively-loaded 21' Portable Vertical with 2-Elevated Radials
Grayline in Matunuck, Rhode Island
The inductively-loaded 1/4WL vertical is constructed out of a half-element from a Tennadyne T-6 log periodic, measuring 21' in length. The base is 1"OD and tapers to .375". It rides beautifully in high winds; there is no need for guys. Set-up requires 8 minutes, with dismantling being done in 3 minutes. Anyone deploying saltwater verticals in DXpeditions might consider using a tapered element. It retracts inside itself; shipping length = 6'.
Portable Vertical Top Hat
Made from Hustler MO-4 mobile stingers
The 21' vertical is crowned by a capacity hat (made from the 3 extra stingers Hustler provides with its MO-4 "short" mobile mast). Measuring 26" each, the stingers are inserted through holes drilled through the end of a short aluminum tube which slips over the (.375") top section. #18 AWG solid (hook-up) wire completes the circuit, lending the top-hat its hexagonal shape. The design exhibits low windloading. The aerial's resonance can be pruned by sliding the top section up and down the top element.
No consideration was given to how much the top-hat would lower the resonant frequency of the 21' vertical. The philosophy was to load it as much as possible with a lossless top hat before bringing it to resonance with a lossy loading coil. A superlative demonstration of the small vertical on receive is provided below.
JA5CJZ 59+20 to 30 dB • Inductively-loaded 21' Vertical • January 28, 2016 • Point Judith, R.I.
The inductively-loaded vertical is operated at seaside locations along the southern coast of Rhode Island.
First Test Site • Point Judith, Rhode Island
The flag seen in the map above identifies Point Judith, R.I., which juts out into the Atlantic Ocean, affording a clear, over-the-water shot to the East, South and south of West. The Northeast path to Europe is also over saltwater across the (Narragansett) bay opening at the southern end of the state. This provides 2 to 5 miles of unobstructed salt water before encountering Newport, R.I. Listening to JAs longpath from this location with only a mobile Hustler whip testifies to the great reception at this site, as heard in the video below.
Listening to JAs Longpath on Hustler Mobile Whip
Point Judith, Rhode Island
A blow up of the area around Point Judith is provided in the map below. The red flag appearing off-shore identifes the second test site, Deep Hole, at Matunuck, R.I. The site is about 4 miles to the west of Point Judith. Both locations exhibit low-noise radio reception with even the most modest of antennas.
The Second Test Site
Matunuck Point, Rhode Island
Deep Hole at Matunuck Point allows public access to the ocean--just over the dune seen in the photo above. 50' coaxial lines are all that is needed to connect the inductive-loaded 21' vertical to the mobile rig in the car. The aerial is affixed to 4x4's supporting the dune fence. The best signal report thus far received from JAs longpath on 40 Meters is 59+5dB. With a shelf extending 300' offshore, Matunuck Point facilitates the siting of vertical antennas directly over salt water.
300' Shelf Protrudes from the Test Site
Deep Hole • Matunuck, Rhode Island
At high tide, the water swamps the shelf to a depth of no more than 3 feet, enabling one to access the verticals with waders (if necessary). Extending 800' parallel to the shoreline, and 300' to the breaking waves, the shelf allows sufficient space to experiment with phased arrays. Smaller waves successively breaking into shore, as seen in the photographs above, indicate the shallow depth of the water over the shelf. If the surfer in the photo stood up, the water would be at his knees.
Shallow Water Extending Out 300 Feet
Matunuck Point, Rhode Island
Swamped twice daily by the ocean, the shoreline at Matunuck Point is nonetheless protected from the pounding surf--except during tidal surges accompanying coastal storms. The site faces due south. The photograph below details the earliest installation of the inductively-loaded 21' vertical, and its attendant, resonant radials, for the purpose of tuning the aerial. An example of the type of propagation possible from locations such as this can be heard in the video below.
European Pile-up • 21' Loaded Vertical
January 28, 2016 • Point Judith, Rhode Island
Portable Vertical "On-shore" Tuning Jig
Matunuck Point, Rhode Island
At Matunuck Point, PVC caps affixed to 4x4 posts along a dune fence accept PVC stubs which serve as stand-off insulators for the two elevated radials. By pulling the PVC stand-offs out of the PVC end-caps, the elevated verticals are removed from the site. On a few occasions in the winter, the stand-offs and elevated radials remained at the test site between operations--reducing installation of the portable vertical to inserting the aluminum element into the PVC insulating tube, tightening a connecting screw and attaching the coaxial feedline. Done.
Portable Vertical Looking East at Dawn
Matunuck Point, Rhode Island
The Portable Base Support
Depicted at the Pont Judith location below, the portable vertical base support is made form a 1" PVC tube, and affixed to the 4x4 post by two metal brackets ($2.45/dozen @ Home Depot). A 1/2" plexiglass sheet was inserted between the metal brackets and the 4x4 post to lift the Z-match coil off the post. Both were subsequently replaced with a metal bracket used to hang electrical conduit, affording the clearance needed by the Z-match coil while eliminating the need for a screw gun to install the vertical. This replacement bracket is discussed shortly.
Portable Vertical Insulating Base Support • Two Versions
The brackets used to support PVC insulating base were changed to allow the base to be spaced off the wooden post.
Below the lower mounting bracket, a shunt coil is wound around the PVC tube. Channels cut into the PVC tube enable the value of the Z-match coil to be varied (1 uh to 2.3 uh) to tweak the feedpoint SWR at varying saltwater sites. Below the shunt inductor is the SO-239 connector, the ground connection for radials and a 1:1 current balun to isolate the feedline. Connection between the top of the Z-match coil and the aluminum element is made by a metal tab cut froom aluminum flashing. All wiring connections are made inside the PVC tube. The system works perfectly.
Fully-developed Vs. Early Jerry-Rigged Prototype
Vertical Base Supports
Initial Failures Due to Multiple Errors
Point Judith, Rhode Island
Initial Errors Result in Failure
The earliest attempts to work JAs longpath using a portable vertical from Point Judith failed miserably, despite assistance provided by Canadian amateurs. In the installation photographed above, several errors compounded to doom the effort despite its location adjacent to the Atlantic Ocean. Amongst the errors are (i) use of non-resonant radials (ii) laid on the ground; (iii) driving a ground rod adjacent to the base feedpoint of the vertical, and then (iv) attaching the radials and shield of the coax to this ground rod. Additional errors include (v) making no attempt to use a shunt inductor across the feedpoint to match the vertical to the 50 ohm coaxial feedline.
In the video below, you can hear how poorly the vertical seen in the photographs above performed. Without assistance from Canadian and Japanese hams, it is likely no contacts would have been made.
Example of Poor Performance of First Saltwater Vertical
EVOLUTION OF THE LOADING COIL
A 3" diameter air-wound coil is inserted across an insulated spacer in the vertical. The coil is then compressed, stretched and otherwise mangled until the vertical resonates at the target frequency of 7.130 Mhz. The coil is removed and measured (with an MFJ analyzer) to determine how much inductance is needed to resonate the vertical. The magic number is 5.4 uh.
Pliable Loading Coil Used During Initial Tuning
The coil is then mounted coaxially within the vertical to see if it detunes the aerial. It does not. The center insulator is replaced with a beefier section of PVC tubing due to high winds encountered at Point Judith.
Second Iteration of the Loading Coil
A section of fiberglass rod arrives from MaxGain Systems (5/8" @ 4' = $7). It replaces the PVC tube as the center insulator in the vertical element. This strengthens the vertical sufficiently to withstand sustained winds encountered at Matunuck Point. The loading coil can continue to be stretched and squeezed to resonate the vertical.
Third Iteration of Loading Coil
After resonating the vertical, the coil is removed and measured with the MFJ antenna analyzer (5.4 uh). I now know 5.4 uh is needed to resonate the vertical using two elevated radials. I re-wind the coil in a more efficient form, so that it will obtain a higher Q and work more efficiently in the vertical. Closer-spacing not only results in the use of less wire, but brings the coil's physical dimensions more closely to the coveted 1:1.5 form factor. So, two strips of plexiglass are clamped on top of one another, and a series of holes are drilled through both. After separation, the two pieces are trimmed with a Dremel tool and threaded onto the loading coil. Done.
Fourth Iteration of Loading Coil
But now the coil is too big. The MFJ analyzer measures it at 7.4uh. I find the 5.4uh spot on the coil, and snip the excess wire off--removing about 1.5 feet. What this shows is that less wire can be used for the same amount of inductance, this reducing the coil losses, by winding the coil in a uniform fashion. The compact, robust loading coil is then re-mounted into the vertical. Attention is paid to leave space between the ends of the coil and the aluminum tubing on each end so as to furtehr reduce losses. When the aerial is set up at Point Judith, it works perfectly. Done.
Final Loading Coil • 21' Portable Vertical
We can tell from the photo that not much inductance is needed to resonate the portable vertical. This is due to (i) the aerial's significant length compared to a full-sized vertical, (ii) its use of a capacity hat, and (iii) the placement of the loading coil near the bottom. How these factors affect the vertical's performance is worthy of review.
Since the current distribution along a 1/4 wave vertical goes from its maximum at the base to its minimum at the top, combined with the fact that the aerial radiates in proportion with this current distribution, it turns out that more energy radiates from the lower part of the vertical. So when we shorten a vertical by inductively loading it we want to place the loading coil up as high as possible because, as far as radiation is concerned, the lower part of the vertical is its filet mignon. Above the loading coil the current and radiation will always taper off (per unit length). From the photograph above we can now see that we placed the loading coil fairly low in our portable vertical--only about 1/3rd the way up. This sequesters maximum efficiency to a mere 1/3rd of its reduced length. Although this was done to strengthen the vertical in high winds, it does not represent optimal placement of the loading coil, electromagnetically.
Buttressed by this new knowledge you might posit, "Let's put the loading coil up higher to get more of the filet mignon at the bottom". This makes sense, and will increase your signal reports. But there are trade-offs which limit this strategy, one of which being the higher you place the coil, the larger the coil must be. Let's see how this and additional see-sawing factors eventually balance out to optimum coil placement.
Left out of our discussion until now is the important fact that the voltage distribution along a 1/4 wave vertical is inversely-proportional to it current distribution. This means that the voltage is minimum at the base of the vertical, and maximum at its top. Imagine a full-sized 1/4-wave vertical with the voltage lowest at the bottom and highest at the top. And then imagine cutting out a section and substituting in a coil. In the shortened vertical you just created the voltage will still be lowest at its bottom and highest at its top. But the gradual rise in this voltage will not occur at the point where you installed a coil. At this spot the voltage abruptly increases--as if to make up for the missing section--and appears as a voltage across the coil.
Let's try to understand this another way by using a real-world scenario. Suppose you want to take a 35-foot, 1/4-wavelength vertical on 40 meters and reduce it to 12 feet by adding a loading coil. And that you've decided to put the loading coil way up in the vertical--like 2 feet from the top--to grab as much of the filet mignon below as possible. That means the first 10 feet of the vertical (below the loading coil) radiates as well as the first ten feet of the full-sized vertical. Bravo! You've cut a nice piece of filet mignon out of that 12 foot vertical. But when you install the loading coil at the ten-foot mark, a large voltage will develop across it because there's only two more feet of vertical above it. Since the voltage maximum sits at the top of the vertical, two feet below--at the top of the loading coil--there is a lot of voltage! And since the bottom of your loading coil connected at the vertical's ten-foot mark--where there's a lot less voltage--a large voltage develops across the loading coil. This is how RF voltage across the loading coil gets bigger the higher up you place it in the vertical. The "omega point" for the coil is reached when the high voltages developed across it exceed the insulating properties of its form, or arc over between windings.
PHASE II: Full-size 1/4 WL Vertical
Tuned at Home QTH
Phase II of the Saltwater Experiment centers on the construction of a full-sized, 1/4 wavelength portable vertical. This larger size raised concerns about whether a single person could manhandle it during installation at windy coastal locations. I opted to tune the full-sized vertical at home. The early prototype was mounted on the back deck of the house, where its mechanical behavior in high winds was conveniently recorded in the photographs below.
Full-size Element Flex Deflection in High Winds
The Mathematical Error
I miscalculate the length of a 1/4 wavelength vertical by dividing 468 by the frequency, and then taking 1/2 of the results. This is wrong because the formula 468/f provides the half-wavelength (in feet) of a wire dipole over ground, taking into account end-effects. My (mis)use of the formula produces results which are too short. The more accurate formula is 246/f -- which is derived from 492/f -- the half-wavelength of a dipole in free-space. This, in turn, is derived the from the classic physics formula 300/f, which provides the length (in meters) of one-wavelength in free-space. Even after writing this part of the story, hams contact me and insist that 234/f is the correct formula to determine the length of a 1/4-wave vertical. And that the same formula is also the correct one to calculate 1/4 wavelength spacing in a phased array. This is, of course, incorrect. Inter-element spacing, for example, must be calculated in free space.
Anyhow, since my fundamental error occurs upstream, disasterous consequences result downstream. Both the vertical and radial lengths were too short. And when Phase III was initiated, the two phased verticals were spaced too close to one another: 32.5 feet, instead of the 34.5 feet of free-space feet required for 7.150 Mhz operation. As detailed shortly, I had to set a third 4x4 post a mere three feet from the first to correct the inter-element spacing error. Both 4x4's, about three feet apart, remain to this day as monuments to my error.
The upcoming photographs beautifully document this error. The reader will note such things as multiple holes drilled in aluminum tubing, the lengthening of elevated radials and the setting of the third 4x4 post perhaps as evidencing the experimentalist's adherence to instrument readings. I say this because I was not aware of the mathematical error, but it did show up in the MFJ antenna analyzer's readins. Thus, when physical dimensions do not agree with mathematical (mis)calculations, the true experimentalist will adjust physical parameters in accordance with his instrument's readings. In my case, it never occurred to me that I had made a theoretical error. My nose was buried in my measuring instrument. This prevented me from realizing the mathematical error had occurred upstream. Luckily, my father, a retired physics professor, monitors this entire process. After noticing my complaints about everything being "too short", he asked me what formula I was using to make the calculations. When I told him, he looked back at The New York Times he was reading while remarking that the dividing the speed of light by the frequency would give me the length of the vertical, if I divided the result by four. Done.
Having been set on the right course, I was able to (re)calculate the length of a 1/4 wavelength vertical resonating at 7.150 Mhz, as provided below. It is constructed of 6' sections of aluminum tubing, available from DX Engineering for about $30.
NOTE: Section 3.5 was added while lengthening the vertical to compensate for the aforementioned mathematical error. It consists of a splice comprised of a 2' length of tubing of the same diameter as Section 3 through which a 3' section of tubing (with the same diameter as Section 4) is inserted. This enables the 2' splice (Section 3.5) to be inserted between Sections 3 & 4, effectively extending Section 3. The resulting joint overlaps are 1' 3.75" and 5.5".
Improved Mounting Bracket
The original metal brackets used for the 21' loaded vertical were replaced by another type which eased installation of the full-sized 1/4 WL vertical at portable locations. The new type of brackets are used to hang electrical conduit, and eliminate use of a screw gun during installation. The vertical base support tube snaps into the bracket at the most vulnerable stage of (single-handed) installation. The brackets also provide the spacing needed between the z-match coil located at the bottom of the base insulator and the 4x4 post, as seen in previous photographs detailing the 21' loaded vertical.
Improved Bracket Eliminates Need for Screw Gun • Removing PVC Tube Sections Reduces Dielectric Losses
Reduction of dielectric losses is achieved by removing sections of PVC tubing not needed for mechanical support. This method may not work at portable locations where the wooden base post is too short to support the aluminum element above it top. In such cases it would be better to use one section of PVC tube which extends above the top of the wooden base post. Shortening the PVC insulating tubes exposes the aluminum base element, thus raising the possibility of feeding the vertical through a gamma-type match--although the 50-ohm match-point likely occurs above the aluminum exposed between base insulators. Any such gamma-type matching scheme requires installing a conductor parallel to the vertical element up to the 50-ohm match-point. As shortly noted, a gamma-type match is facilitated by mechanical means used to feed the vertical.
Mechanical Feedpoint Connection
For reasons having nothing to do with electrical design, I decided that the electromagnetic energy should be equally applied to both sides of the aluminum tubes. I did this because whenever I look at devices wired by RF engineers, I see physical symetery rivaling fine art sculptures. Gentle arcs in wires; right angles blunted. Twin feedlines drape symeterically down to a switching box suspended below and between the dual parasitic-driven elements by its own caternary line.
Symetery of RF Systems • 2-element Reversible Moxon • W1ZY • New York • 2005
Such aesthetic qualities are an aspect of how RF systems work well. Along such lines, a stainless steel machine screw passes through the PVC insulator and the base of the aluminum vertical element. The hole through the PVC tube is enlarged to the diameter of aluminum spacers which sandwich eith side of the vertical element, and then squeeze it when the stainless steel screw is tightened. This makes an electromagnetic connection at both sides of the aluminum element.
Feedpoint Connection Made on Both Sides of the Vertical Element
It also causes the machine screw to protrude from both sides the PVC tube, affording connection points for the center wire of the coaxial feed on one side, and a RF choke to ground on the other (to bleed off static build-up). The stainless steel machine screw also prevents the aluminum element from slipping through the bottom of the PVC tube. Removing it allows the vertical element to be slipped in and out of the base insulators at seaside locations without having to remove them from the wooden support post. Even this step can be accomplished by snapping them from the metal brackets that hold them to the wooden support. To feed the vertical using a gamma-match, threaded rod could replace the stainless steel screw, in which case the length of the threaded rod constitutes the spacing between the gamma-match arm and the vertical element.
Initial Testing with 2 Elevated Radials
The Saltwater Vertical Experiment strives to use the same elevated radials with each vertical prototype. This allows the same base/radial system to be used with different types of verticals. To tune the full-size vertical, the radials used with the 21' loaded vertical (Phase I) are connected to its base.
Tuning the 1/4 Wavelength Vertical • Common Mode Choke
Resonating the 21' loaded vertical centered on adjusting its loading coil while keeping an eye on readings in the MFJ antenna analyzer. There were no calculations predicting physical dimensions governing its construction. It was assembled using available scraps, beginning with its top-hat--which was made as large as possible--followed by the vertical element assembled from sections of a T-6 in storage. The only variable was the loading coil, which was stretched/compressed until resonance was obtained. In the case of the 1/4 wavelength vertical, there is no top-hat or loading coil. The only variable to bring the system to resonance is the length of the vertical element. An easy proposition until one recalls that I miscalculated its resonant length--a problem compounded by my failure to realize this fact. Thus, when the vertical resonated at 7.650 Mhz, I assumed the radials needed to be lengthened.
Lengthening Radials to Compensate for Miscalculating Vertical Length
Naturally, it turned out the radials needed to be lengthened by the same amount lacking in the vertical in order to resonante the aerial on 7.150 Mhz (SWR: 1.5; X=40). When excited with 100 watts, DX stations were worked with common-mode intereference perplexing a television audio system. After adding an "ugly balun" to the feedline (wrapped around a mason jar), and ferrite bead chokes on the audio equipment, the common-mode interference was reduced, but the "locking" quality of the SWR and resonance curves remained. Being too windy to test the quarterwave vertical at any seaside location, I opted to build the second 1/4 wavelength vertical in order to phase them. A "test range" was established in the woods, partially to eliminate the common-mode problem related to mounting the full-sized vertical to the house.
PHASE III: PHASED VERTICALS
Phasing Two Full-sized 1/4 Wavelength Verticals
For several days I tramp through the woods with a compass and a roll of mason line taking measurements collated on paper. Back in the workshop, I draw up a crude map highlighting openings in the canopy, and skew its polar coordinates to reflect the true-north readings not provided by the compass. This allows me to determine possible azimuth orientations for the phased verticals. The best I can do is site the verticals slightly north of East--covering Europe, Africa and South America--and slightly south of due West, covering the Pacific, Australia and New Zealand.
It should be noted that a phased vertical array is not a high-gain antenna. Adding a second vertical and phasing it with the first only doubles your signal strength. Maybe a little bit more, if you are meticulous with the tuning. Aside from their low take-off angle, and the dispersal of your 3 to 4 dB increase in signal strength over 120 degrees, the main advantage of phased verticals is their rejection of rearward signals--nominally 25 to 30 dB. So, if situated on the East coast of the United States, orienting a pair of phased verticals to the east reduces stateside QRM coming from the west. As later discovered, and as shortly documented, this reduction of stateside QRM depends upon propagation. For in the late-afternoon, as the band opens up to Europe, stateside signals to the west begin to go down when the array is flipped to the east. By 8 o'clock or so, when the propagation begins to go long, the reduction of American signals increases. And as night fully envelopes, the 40 meter phone band can appear devoid of stateside signals. In fact, the first time I scan across the band after installing the second vertical--and before I added the remote switching relay--I think something is wrong with the antenna because the few American signals I can hear are so weak. Below S-9. I go outside with a flashlight to rearrange the cables to reverse the array's directivity. When I return to the workshop, the same scan across the same frequencies produces a bevy of powerful stateside signals. Dayem. It's alive!
But these events are yet to unfold. They are weeks away from the cold, early-March afternoon when, as snow flakes begin to fall, I find myself in the woods pushing a wheel-barrow along what would become the well-trampled path to the West vertical. It ferries a 50 lb bag of concrete, a five-gallon bucket of water and a post-hole digger. After the hole is dispatched and some gravel thrown in, an eight-foot 4x4 is tipped until one end thunks down deep in the hole. The cement follows, evenly distributed around the post. The level of a carpenter's square assures the post is upright. For the next fifteen-minutes, water trickles from the bucket and is allowed to seep into the Quickrete cement. About an hour later the cement is set. The 2x4 serving as a base for the vertical is attached to the 4x4 post with 3" sheetrock screws later replaced with 8" carriage bolts. The entire episode takes less than two hours. Done.
Setting the First 4x4 Post
After setting the first post, the two counterpoise wires used in Phase I are strung under the 1/4 wavelength vertical to provide a counterpoise for initial tuning. Which does not go well. The vertical resonates on 7.6 Mhz, and shows a feedpoint impedance of 45 ohms with a healthy reactive component. This is not good, and manifests the fact that the formula I am using, 234/f, is wrong. Although I don't know that yet. I tune the vertical by lengthening the counterpoise wires, which works; the vertical now resonates in the 40 meter phone segment, but with the reactive component and high feedpoint impedance. Back in the workshop, the other end of the feedline shows an impedance of around 90 ohms. I could use the transmatch to tune this out if it was not for the fact that the transmatch is already being used to match the exciter and the amplifier. To top it off, my (mis)calculation calls for the vertical to be a lot shorter than it actually needs to be, and, thus, I never ordered enough aluminum from DX Engineering to make it the correct length. I stop the vertical experiment altogether in order to resolve these problems. Besides, the snow flurries outside transformed into a blizzard. And who wants to work outside in that?
Snowfall Curtails Saltwater Vertical Experiment
Turning inward, I shift focus to reconditioning the Heathkit SB-221 amplifier--something on my bucketlist for the past 35 years. To achieve a 1:1 SWR between it and the exciter liberates the tuner to match the amplifier to the antenna feedline. This, in turn, allows testing of the vertical which may lead to figuring out what's wrong with it. At least so I think. So, while reading and re-reading elevated-radial technical papers at night, by day I strip down the Heathkit SB-221 to its bare chassis, removing all components and wiring assemblies. I throw them into a cardboard box for later sorting. I am not scared.
Upright recycle bins provided by the local town government serve as operating tables, enabling me to walk around the amplifier while working on its revitalization.
For the next 6 days I listen to podcasts of NPR's "Car Talk", with "Click and Clack, the Tappet Brothers" troubleshooting mechanical problems as I do the same. I wet-sand the chassis before reassembling the amplifier--which goes easily since it is a kit.
Final improvements include: re-capping the HV power supply; adding the Harback rectifier/metering and soft-key boards; grounding the grids; removing the "CB filter"; re-tuning the input circuits; removal of Rich Measures parasitic chokes; new "french" parasitic chokes; rewound the filament transformer; new ceramic capacitors; removal of black paint from RF deck; DeToxit cleaning of potentiometers, bandswitch & relay contacts; cleaning and rewinding the tank coil; rewiring of input & output bandswitch wafers; new SO-239 connectors; installation of AC transient spike suppressors; new grommets; new coaxial lines; new circuit breakers; disabling of 120 VDC cathode cut-off bias; rebuilding of 120 VDC power supply; oiling cooling fan; acoustic silencing of cooling fan mount; removal and cleaning of tube sockets; cleaning of tube socket connectors; cleaning of tube pins; re-painting rear air intake grill; etc. Done.
The Completed SB-221 Restoration
Constructing Phased Verticals
Installing a vertical element is effortless compared to the construction of its elevated-radial system, which takes weeks. There is no way to speed up this job, and you will be consigned to commuting to the site many more times than you anticipate. Assembling tools in a small bag removes one more thing "to do" when heading out to the work site. This may run contrary to those who subscribe to the view that four elevated-radials are sufficient for reasonably efficient operation of the vertical. This view was retracted in 2012 by its main progenitor, Rudy Severns, N6LF, in a lengthy, technical paper reporting the results of meticulous field studies of elevated radial systems (http://rudys.typepad.com/files/qex-mar-apr-2012.pdf ). As things turn out, 20 to 25 elevated radials stabilizes the behavior of the vertical; it begins to behave in accordance with textbook theory. This eases the meticulous tuning required when two verticals are pressed into a phased vertical system. This is partly due to the symeteric distribution of displacement currents between the higher number of elevated-radials, thus reducing the problem of asymetric currents inherent in 4-elevated radial systems. The larger number of elevated radials also more effectively screens the vertical from the ground, thus reducing the need for a "chicken-wire" or buried radials to reduce ground losses--as recommended for the 4-elevated-radials scheme. The take away is that you will spend a significant amount of time in the field constructing the elevated radial system if you wish to end up with an efficiently-operating phased vertical array. From my experience, the assembly of a toolkit is both the first step and last chance to procrastinate.
Tool Kit for Building Elevated Counterpoise Systems
I used a canvas tool bag available from Harbor Freightfor $6. I loaded the following tools and materials into it.
Everything should remain in the tool bag at the end of the day. This increases productivity in the field by eliminating the need to put the tools away at night, only to re-assemble them at the start of the next work session.
Because I built the phased verticals in a wooded grove, I use a wheel barrow to ferry tools, a step ladder and cement bags out to the site--much in the same way that a contractor uses a work truck to do the same thing. Upon arrival, the wheel barrow serves as a means of laying out tools for easy access, and as a depository for wire and twine remnants properly disposed of later back at the workshop. This keeps the woods clear of debris of possible harm to wildlife--especially tangled webs of fishingline.
Wheelbarrow Ferries Tools & Materials to Work Site
The general axiom is to approach construction of your phased vertical array in the same way that a carpenter approaches the construction of a house. Devise some means of organizing and transporting the tools, and of removing debris at the end of the day to keep the site clean. Why? Because installing a phased vertical array can get complicated. Its counterpoise system demands precision. You will find that the threading of pre-measured lengths of wires through shrubbery and undergrowth in a wooded area will be frequently delayed by unforseen snags. At times it may appear that every, single possibility for a line to get snagged is actualized. Many fractions of dBs can be lost when such frustrations are encountered during construction.
Zen and the Art of Phased Arrays
The reader might ask why I have focussed on the assembly of a toolkit, or how it eases the daily trek out to the antenna site. Although these things are self-evident, I include them in this narrative to buttress the state of mind needed to tackle this project. Sure, you can bang it out in an afternoon in time to show it off on the local, 40-meter cloud-burner's net. Or throw it together for yet another eHam article. But there is another approach. An approach we shall term the "Zen" of constructing the array.
Verticals are finicky. The bands are strewn with carcasses of "verticals that don't work". This feeds the adage that verticals "radiate poorly in all directions." Yet, once in a while, one will encounter a vertical standing proud and tall holding court with DX stations in the late-afternoon sun. Or phased verticals disappearing into the noise when their directivity is flipped by old timers. One way to achieve such performance levels is to adopt an attitude in keeping with the array's finicky nature. A good mental starting point is to imagine yourself alone, before driving in the first post-hole, pausing to visualize your upcoming accomplishment. And that getting from here to there will take at least a couple weeks. At that point the phased verticals you are about to build already exist in your mind's eye. And all you have to do to get there is begin their physical construction by measuring each elevated radial wire precisely before stringing them symeterically from the base of each vertical, and then finishing off this part of the job by making sure they are all equally taught. And what to do where the elevated radials intersect? Each night, after finishing up in the field, you sit in your workshop fashioning insulated spacers from PVC tubes, replete with end-slits cut at the same complimentary angles as exhibited by each pair of intersecting wires. To make sure you got it right, you return to the field with a flashlight and a step ladder to pre-fit the insulators slated for installation the next day. Well, maybe you don't have to go that far. But you get the idea. When in the field working, you leave your body and watch yourself from above incrementally transfer into reality the antenna you've been imagining for months.
Attitudes like these minimize construction errors. For with every wire you splice, every solder connection you make, exists the potential for diminished performance. Fractions of a dB are lost when you implement a fudge-factor, or take a short-cut you know you shouldn't take. Since the difference between theoretical and actual performance is you, the disparity is under your control. Your attitude during construction is reflected in how well your aerial ends up working.
One's mental attitude plays a role in human endeavors beyond building antennas. It is found manifest, for example, in athletics. How often a golfer sinks a putt, a wide-receiver catches the pass, or how quickly the runner crosses the finish line are all affected by mental attitude. Mental attitude is a core element of all championship performances. The same holds true with building antennas. For before construction begins, you are the golfer before teeing-off, the receiver before hut-hut is heard, the bent runner readied for the starting gun. Envisage the idealized antenna at every step of building it. Go the extra mile when implementing solutions. Take a break when frustrated--even if you just took a break. Smokers--light up if you got 'em, for you are free to chain-smoke. This is the way of the antenna-builder. A mindset not known to those who purchase commercial antenna systems.
Dealing with the Counterpoise System
Run Catenary Lines Around the Verticals
This phased vertical array employs two elevated-counterpoise systems electrically-isolated from one another. Each consists of thirty (30) 1/4-wavelength wires--for a total of sixty (60). They are strung out from the bases of the verticals in symeterical patterns. The far ends have insulators, and are tied off onto catenary lines run around the perimeters of both verticals. Eyehooks, sheetrock screws and other non-invasive fasteners are used to anchor the catenary lines to trees. When tensioned, the catenary systems are able to suspend the elevated radials about 12 feet above the ground. It is necessary to run the catenary lines in order to evenly distribute the radials from the bases of the verticals. No way around this. The catenary lines took a week to run around the verticals in the woods, at a time when the foilage (and insects) had yet to arrive.
Short sections of PVC tube serve as end insulators. To keep the two elevated-counterpoise systems electrically insulated from one another, 6" PVC tubes serves as stand-off insulators wherever two counterpoise wires from opposing systems intersect one another.
End-insulators Made of 1/2" PVC Tubing
Catenary Lines Assure Symeteric Distribution of Elevated Counterpoise Wires
Radial Intersecting Points Electrically-Insulated and Spaced 6"
Catenary Lines Anchored to Trees • Non-invasive Fasteners
Wrapping Lines Around Tree Kills the Tree by Removing Ring of Bark
Construction techniques such as these harp back to the original wireless pioneers, who used readily-available materials--combined with their imaginations--to build their antenna systems. All of this has changed with the commoditization of ham radio equipment. A lot has been written about the relationship between elevated counterpoise systems and vertical elements in phased arrays. The general axiom is that four (4) tuned, elevated radials will work as efficiently as 32 buried radials. This is not what I found in Phase III of the Saltwater Vertical Experiment.
Near & Far Fields
Two concepts central to understanding how verticals work are its "near field" and "far field". The near field involves how the immediate surroundings determine how efficiently the vertical ends up radiating. In practical terms, this zone extends about a wavelength around the antenna. The far field has to do with how terrain extending out several miles from the antenna sculpts its directive pattern. Generally speaking, the near field determines the size of the radiation plot, while the far field determines its shape. This concern gives rise to the simple question: "How does the energy applied to the vertical element by the center of the coax get back to the shield of the coax?" The answer is that it completes the circuit by flowing through the portion of the earth contained within the near field of the vertical.
In simplistic terms, you can visualize the transmitter putting power into the center conductor of the coax in the shack, and then this power goes along the center conductor to the vertical in the field. Once it hits the vertical element, it needs some kind of path back to the shield to complete its circuit. In a ground-mounted vertical, this "return" path is provided by the earth, itself. Since soil conductivity is low, the displacement currents making their way back to the shield of the coax via the ground do so as if passing through resistors. You can think of it as a resistor placed in series with a 12 volt lamp, causing the lamp to dim. The more resistance encountered by the displacement currents, the less power is radiated by the vertical. The wasted power ends up heating the earth in the immediate vicinity of the vertical. To reduce such losses we need to reduce the resistance of the path taken by the displacement currents. And this is accomplished by burying as many radials as possible around the base of the vertical in an attempt to "short out" the "strings of resistors" represented by the ground conductivity in our model. The more wires you bury, the more strings of resistors you short out. None of this has anything to do with how well the vertical performs as a DX antenna--in terms of its predominant angle of radiation. That aspect is developed in the "far field" which we have yet to discuss.
In review: The near field has to do with the immediate vicinity of the antenna, and determines how much power ends up getting radiated. It encompasses several wavelengths out from the vertical. We try to increase the antenna's efficiency by burying radials into the earth to provide paths other than the lossy earth for the vertical's return currents.
There's another way of offering a path for the return currents in a vertical, aside from a buried radial system. And this is through the use of "elevated radials", or more correctly "elevated counterpoise wires". When we use elevated counterpoise wires, we are lifting the feedpoint of the vertical up and away from the lossy ground. The displacement currents begin to flow more through the elevated radials than the lossy earth. Thus, the higher we elevate the counterpoise wires, the more we decouple the vertical from the earth. This reduces ground losses and thus increases the vertical's efficiency. To ultimately decouple the return currents from the lossy earth, we string out as many "elevated radials" as possible from the base of the vertical. Using only two or four elevated radials requires that they resonate on the same frequency as the vertical to encourage symeterical current distribution amongst them. As the number of elevated radials increases, the whole counterpoise system begins to loose resonance, thus alleviating the need to cut each radial wire to the exact length. Return currents are also more evenly distributed, which reduces the amount of current carried by any single wire.
When using small numbers of counterpoise wires, the elevated vertical's efficiency can be increased by burying radials or laying out chicken wire beneath the elevated radials to shield them from the lossy earth. Use of a large number of elevated counterpoise wires--above 30--renders such measures to no advantage because the larger system effectively shields the antenna from the lossy earth.
So there you have it: a few paragraphs explaining the "near field" of a vertical antenna which will make any electrical engineer or physicist cringe. Is this actually how it works? No. But it serves as a starting point to dispell misinformation about the relation between vertical antennas and soil conductivity. Many think that if you have "good ground conductivity" you want to couple the vertical to the ground. Or that a vertical "wants" to "work against the ground". The fact of the matter is that in all instances except that of saltwater, one wants decouple the vertical from the earth as much as possible. Thus, if you ground-mount your vertical, you need to lay out or bury as many radials as possible to offset the resistance of the lossy earth. If you raise the vertical above the ground, you want to string out as many "elevated radials" as possible. And if you can string outonly a small number of "elevated radials," you can improve your vertical's efficiency by doing so over a buried radial system, or by laying out chicken wire beneath the antenna to further shield it from the ground. Further notions of adding salt or "watering" the ground beneath a vertical to enhance its efficiency, or substituting a radial system with a series of ground rods should now be dispelled. As well as the notion that vertical antennas will "play well" when installed over high water tables or on the shores of fresh water lakes. None of these are true. The difference between excellent and poor ground conductivity is measured in fractions of a dB. In both cases, and those inbetween, enhanced performance can be realized by taking measures to decouple the vertical from the earth. The take away is that the "ground" or "earth" is not a friend of the vertical, as far as the near field is concerned. The only near-field friend the vertical has is salt water.
Salt Water: A Unique Situation
Why is salt water so coveted amongst vertical enthusiasts? Why does locating a vertical on or near salt water enhance its performance? Taking all we have learned about the "near field" thus far, the answer is partially revealed by the table below.
We can use scientific notation to express the soil conductivities in Table 1.
VERY POOR - (1xe-3)
POOR - (2e-3)
POOR - (2e-3)
GOOD/AVERAGE - (5e-3)
VERY GOOD - (3e-2)
SALT WATER - (500e-2 or 5000e-3)
The soil conductivites can now be expressed as integers raised to 10-3.
VERY POOR - 1
POOR - 2
POOR - 2
GOOD/AVERAGE - 5
VERY GOOD - 30
SALT WATER - 5000
At RF frequencies, salt water conducts:
It conducts better than soil by 2 to 3 orders of magnitude. What does this mean?
Orders of Magnitude
What is an order of magnitude? An order of magnitude simply means "ten times more". So, for example, if we increase our transmitter power from 1 watt to 10 watts, we have increased it by a factor of ten, which is an order of magnitude. And if we increase it again--this time going from 10 watts to 100 watts--we have increased our power by yet another order of magnitude. Doing the same thing again--this time going from 100 watts to 1,000 watts--means we end up running 3 orders of magnitude more power than the original 1 watt. On the receiving end, each order of magnitude increase in our transmitter power registers a 10 dB increase in our signal strength. So, if we increase our transmitter power by 3 orders of magnitude, our signal report will increase by 30 dB.
Such comparisons serve to provide a ballpark idea of how much better salt water conducts at RF frequencies than any type of soil. For most soils ("very poor" - "good/average"), salt water conducts about 30dB better. And for the best possible soil possible ("very good"), salt water conducts about 20 dB better. Does this mean that a vertical installed at the ocean will be 30 dB louder than when it is ground mounted inland? No--although these numbers do correlate with my own field experiments. What it does mean is that it is impossible to make up the 2 to 3 orders of magnitude difference between the conductivity of salt water and soil by adding salt to the ground beneath a vertical, or by watering it. Nor does installing a vertical aside a freshwater lake, or in an area with a high water table, improve the vertical's near field ground conductivity. What the numbers do show is that something special happens when salt water is found beneath a vertical.
With regard to the near field, what this means is that the salt water vertical does not need as extensive a ground radial or elevated counterpoise system as an inland vertical does to achieve the same efficiency. When a vertical is situated near or over salt water, there is no need for scores of ground radials to "short out" the "series of resistors" representing poor soil conductivity at inland locations. You can get away with as few as 2 elevated radials. Why? Because in the case of the salt water vertical, it is not mounted over "lossy earth". It is mounted over a beautifully conductive plane that enhances the flow of (displacement) currents. No need to "bury" ground radials to increase its conductivity, or string out 30+ "elevated radials" to shield the vertical from it.
And what about inland hams using vertical antennas and phased arrays? What does this mean to them? Their takeaway is to focus on their ground systems. For it is within the near field of inland vertical installations that extensive ground systems close the gap between the high-conductivity of salt water and the low-conductivity of soil. At a coastal installation, the high conductivity of salt water means that a less-extensive ground system is needed to achieve a high degree of efficiency compared to an inland installation, where the poorer soil conductivity necessitates a more extensive ground system. An inland vertical can operate as efficiently as a salt water vertical. It just takes a lot more wire.
Momentarily removing the salt water scenario from further consideration, and restricting our discussion to inland vertical installations, many technical papers point to the same conclusion; namely, that there is a point after which adding radials (whether buried or elevated) to a vertical does not increase its near field efficiency. There is a numerical limit. In the case of buried radials, the limit lies somewhere between 64 and 120 radials. If you add more radials above this range, the efficiency of the vertical does not increase--irrespective of soil type! The limit to the number of radials dovetails perfectly with the observation that the soil conductivities provided in Table 1 span a range resolving to a factor of about 50. This range is so miniscule compared to the orders of magnitude difference between the conductivity of salt water and all soil types that it undercuts the notion that a vertical's efficiency is limited by the soil conductivity of its location. A vertical in the desert, for example--with its "very poor" soil conductivity--can achieve the same efficiency as the vertical installed over "very good" ground because the difference between their soil conductivities is not technically insurmountable. Radials can be added to the vertical in the desert until it exhibits the same near field efficiency as the vertical over "very good" ground--which naturally uses fewer radials. Although both verticals will eventually reach the point where adding more radials doesn't enhance their efficiencies, the vertical over "very good" ground will require fewer radials than the vertical over "very poor" ground before this point is reached.
Conclusion: Near Field
The near field has to do with the array's interaction with its immediate environment, which boils down to how efficiently it radiates. Most near field parameters can be controlled by the builder. In the case of our phased vertical array, the near field parameters include:
The second concept we promised to cover is the Far Field.
The far field has to do with how the local terrain, extending out hundreds of wavelengths from the antenna, shapes the antenna's radiation pattern. Obviously, the far field of a 40 meter antenna canot be controlled by its builder--aside from relocating the antenna. Which is why the Saltwater Vertical Experiment is so interesting: we move the vertical to different locations, which is tantamount to altering its far field. We can place it various distances from the shore. Or install it right on the shelf that extends 300' away from the shore--at Matunuck Point--and see if anything happens in the far field when the moon floods the near field with salt water. With the soil conductivities listed in Table 1, this would be an interesting experiment.
But what is the Far Field? The far field is the terrain extending about 3 to 5 miles from the base of a 40 meter vertical. It is over this "far field" that the antenna's final directive pattern is sculpted--including how far above the horizon a vertical's low-angle lobe will hover. You can see what we are talking about in the radiation pattern graphs produced by antenna modelling programs, such as NEC.
If you look at modeling plots for a vertical, you see the vertical, which sits at the center of the graph, with two lobes coming out nearly perpendicular to it. If you look closely, you will notice the lower edges of these lobes do not hug the X-axis of the graph. The bottomside of the lobes execute a gentle, upward curve as they move out along the X-axis--sort of like the bow of a motorboat speeding through water. The bottom edge of the low-angle lobes is of highest concern to DXers. The lower this part of the curve gets to the X-axis, the lower the vertical's "take-off" angle. Making this "take-off" angle as low as possible is the Holy Grail sought by antenna designers, and the Ark of the Covenant used by SuperStations when pinning thousands of S-meters during contests. How does this work?
Let's suppose the "take-off" angle is zero (0), and thus the low-angle lobe is parallel to the horizon. In such circumstances, the radio wave propagates off the antenna and travels towards the horizon skimming the surface of the earth. By the time the radio wave propagates about 12 miles out, the curvature of the earth begins to cause its surface to drop away from the radio wave. As the wave continues outwards, the surface of the earth continues to drop away. Eventually, the radio wave is hundreds of miles above the surface of the earth. At this point, the radio wave would continue out into space if it was not for the ionisphere, which reflects most of it back towards earth. After doing so, the radio wave continues to travel, but on a collision course with the earth because the ionisphere has bent its trajectory back towards the ground. At a point about equal to the distance the radio wave has thus far traveled, it arrives at the surface of the earth. This is the point where the radio wave completes its first "hop", whereupon part of it bounces off the earth and heads skywards----on its way to another rendezvous with the ionisphere. The maximum single-hop distance for the F2 layer is about 4000 Km, and 2000 Km for the E layer.
The distance the radio wave travels before making its first terrestrial "bounce" is called the "skip zone"or "skip distance". For the purposes of DXing, we want this "skip zone" to be as long as possible because every time the radio wave "bounces" off the ionisphere or the earth, it gets weaker. Conventional wisdom estimates the attenuation at about 10 dB per hop. This means that your signal report from a DX station loses ~10 dB with every "hop" it makes on its way to the DX location. As the reader may have already deduced, lower take-off angles require fewer hops than higher take-off angles to get to the same DX location.
Let's re-rack and go through this explanation again--this time assuming the predominant "take-off" angle is not parallel to the horizon, but 20 degrees above it. Under such circumstances, the predominant lobe radiates energy at 20 degrees above the horizon. Within the near and far fields, a smaller component will radiate at negative angles--meaning at angles below the horizon. Within the vertical's far field, these negative angle components will be reflected by the local terrain and eventually re-join the predominant 20-degree component--which has not been reflected by anything. The point at which the two angular components recombine sculpts the vertical's low-angle component. When the two angular components merge constructively, the vertical's low-angle component is enhanced. When the two angular components merge deconstructively, the vertical's low-angle component is not enhanced. The degree to which the two angular components end up recombining is determined by the extent to which the radio wave's polarization and phase are shifted when reflected by the local terrain. Should there be no shift, the two components recombine constructively, thus lowering the vertical's "take off" angle.
As the reader might have already deduced, inland terrain--with its poor soil conductivity compared to salt water, topographical undulations and geological formations--does not reflect the negative-angle component well. Whatever energy is reflected off the ground does not recombine constructively with the low-angle lobe because its polarization and phase have been dramatically shifted. That is why verticals do not work as well in regions with poor soil conductivity, or in valleys or cities, compared to when their far fields are proximate to the ocean. When they are, the conductivity of salt water, combined with the ocean's planar surface, enhances the reflection of the negative-angle component of a vertical's radiation. This reflected component recombines with the predominant low-angle lobe a lot more coherently than is the case over land. How much more? Almost all of it. The conductivity of salt water, combined with its virtually mirror-smooth surface, redirects almost all of the negative-angle radiation to the low-angle lobe. This extends the low-angle lobe, while skewing its lower-half downwards towards the X-axis. This causes salt water verticals to exhibit lower angles of radiation than inland installations.
Salt Water Extends a Vertical's Low-Angle Lobe
To the left, the vertical over land. To the right, the vertical as it is relocated away from the ocean.
21' Saltwater Vertical Working VK6APZ Longpath
January 28, 2016 • Point Judith, R.I.
You can visualize why RF does this over the ocean's surface by remembering what the ocean looks like on a sunny day. If the sun is directly overhead, you can look down into the water and see the fishes swimming around. If the sun comes in at an increasingly lower angle, at some point it starts glittering off the surface and you cannot see down into the water.
The sun's light is as much electromagnetic radiation as is the energy radiated by the vertical. It's just that its frequency is so high, and its wavelength so short, that the contours of the ocean's waves and ripples--which are many wavelengths longer than sunlight's--cause the sun's refelction to glitter and sparkle. In the case of the 7 Mhz vertical, its 40 meter wavelength is much larger than the countours of the waves and ripples of the water. Therefore, at 40 meter resolution, the surface of the ocean appears to be a flat surface exhibiting high conductivity. At 7 Mhz, it acts as a smooth mirror reflecting most of the negative-angle radiation emitted by the vertical. When this reflected component merges with the vertical's low-angle lobe--kilometers out in the antenna's far field--it combines constructively, thus enhancing the low-angle component of the vertical's radiation pattern. Inland, this is not true. Geological formations and topographical undulations are perceivable at 40 meter resolution. They constitute "ground clutter" to the negative-angle component of the vertical's radiation. When encountering the poor conductivity of all soil types, the small amount of this component that makes it way back to the low-angle lobe does not recombine with it. This is why the antenna modelling plots of verticals situated over soil never show the low-angle lobe coming all the way down to the X-axis.
The Pseudo Brewster Angle
This Section is Unfinished
Richard Feynman & The Pseudo Brewster Angle
The Brewster Angle is from physics. 1811, to be exact. You can read Dr. Brewster's original peper here. https://books.google.com/books?id=U-U_AAAAYAAJ&pg=PA125&hl=en#v=onepage&q&f=false
The Brewster angle has to do with figuring out what happens when a "pencil of light" (aka. light beam), let's say travelling through air, hits some other medium, like water or glass. When it does, part of the light beam is reflected off the surface of the water or glass, and part of it is refracted by the medium--meaning it passes through the medium. The angle at which the "pencil of light" strikes the medium determines how much of the light beam ends up reflecting off the surface of the water or glass, and how much of it ends up passing through the medium as a result of being refracted by the medium. Another thing that determines the percentages of the light beam that end up being reflected and refracted is the "index of refraction" of the medium, itself.
Now, when a light beam bounces off of something, or passes through it, the photons don't actually richochet off the substance. Or navigate through it, if the substance is translucent. What happens is that the photons are "absorbed" by the substance. They disappear. They do so by "jiggling" electrons in the substance. This, in turn, causes the electrons to "re-radiate"--just like the passive elements of a yagi do (e.g. director, reflector). But in this case the electrons "re-radiate" by emitting another photon. That's how photons are "reflected" off a substance, or "pass through" a translucent one. It's like a relay race. Photons in the light beam hit the substance and excite electrons in the substance. These excited electrons then emit photons in order to return to their lower energy state. These "re-radiated" photons then almost immediately hit another electron, jiggling it. It emits a photon. This goes on and on and on through the substance until the electrons at the opposite surface of the substance emit photons which do not strike anymore electrons, but simply continue uninhibited outside of the substance. This is an over simplification, and assumes the substance is in a perfect vaccum. But it serves the early stage of our understanding of the Pseudo Brewster Angle.
Now, each time a photon jiggles an electron, certain aspects of the light beam change. One of these asspects is its polarization. As things turn out, assuming the light beam heading towards the substance is not polarized, being reflected by the substance polarizes it, and being refracted by the substance also polarizes it, but not so much.
the angle the sun has to be to the ocean in order for the glare of its reflection to prevent you from seeing into the water. Or the angle the sun has to be at in order for the glare off a window to prevent you from seeing inside a building. Actually, the Brewster Angle is a lot more intricate than this. Let this simplistic notion suffice on the first pass of a more thorough explanation. Having said that, if the sun gets lower off the water than the Brewster Angle, it glare continues to prevent you from seeing into the water. And if you look closely, you will notice that you cannot see into the water even in parts where the glare of the sun is not reflecting off the surface of the water. The same holds true if you are iunderwater. When you look up amd away at a certain angle, you cannot see the sky above you. All you see is a rippling reflection of everything beneath the water. If you look straight up, it disappears and you can see clearly the sky above. You can see the same thing when looking into an aquarium. The Brewster Angle is the angle at which total reflection occurs.
Reflection of turtle off surface of water is due to the Brewster Angle
WORKING ON THIS SECTION NOW:-
The Pseudo Brewster Angle is used in RF engineering. It represents the lowest elevation angle at which an antenna's radiation pattern is 6dB below its isotropic value.
Below the "Pseudo Brewster Angle" the direct and reflected waves do not recombine in a constructive fashion (they substract). At angles above it, they combine constructively (they add up). This is why antenna plots show the modelled pattern receding from the "perfect ground" isotropic pattern at elevation angles below the Pseudo Brewster Angle--which is arbitrarily defined as the point where the difference between the two is 6 dB. As the elevation angle gets lower, this 6 dB of attenuation increases. Maximum attenuation occurs when the elevation angle is equal to the horizon (0-degrees). This increasing amount of attenuation measures how well your vertical is performing at low elevation angles.
Since this interesting phenomenon is developed in the far field of the antenna, it is sculpted by the surrounding terrain--as far as several miles out--by geological undulations, mountains and urban structures. And as you might suspect, such terrains exhibiting poor soil conductivities attenuate low angle performance to a far greater extent than a planar far field exhibiting high conductivity--such as an ocean. Between the two extremes one finds situated a majority of ham radio vertical installations.
angles exhibited at dispersed over and obstructions and poor soil conductivity undulations or onstructions the more obstructions you haveproliferent landscape undulations, geological obstructions and There is little you can do to improve performance other than relocate the vertical, which is why hams in the desertYou will see the the low-angle lobe getting weaker and weaker. Above the Pseudo Brewster Angle, the plot will show the low-angle lobe getting stronger and stronger. This is because above the Pseudo Brewster Angle, the reflected component of the negative-angle radiation recombines constructively with the low-angle component far out in the antenna's far field. This enhances the low-angle component of the vertical's radiation pattern. For DXing, we want the Pseudo Brewster Angle to be as low as possible to maximize the lowest-angles of the antenna's "take off" lobe. This causes the front of the outboard motorboat discussed earlier to level off so close to the X-axis that it appears to be sitting flat on the water. And this is exactly what the bottom edge of the vertical's low-angle lobe looks like when plotted over a perfectly reflecting plane. When the same modeling program is set to model the vertical over salt water, the outcome is practically the same; the low-angle lobe begins to drop off at 0.1 degree! The takeaway is that the Pseudo Brewster Angle is determined by the far field of the antenna. The lower the Pseudo Brewster Angle, the more the bottom edge of the low-angle lobe hugs the X-axis. Which means more energy radiated at the lowest possible angles. Which means the fewest possible hops to the DX location.
REVIEW OF ELEVATED COUNTERPOISE SYSTEM
The Ground System Determines How Much Power is Radiated by the Vertical
An old timer summed up the role of a vertical's ground system when stating, "It determines how much power the vertical radiates". Another well-known ham equates the ground system as a footing needed by the transmitter to "push against" when jiggling electrons up and down the vertical element. Others visualize the ground system as a path allowing for "return currents" radiated by the vertical element to make their way back to the shield of the coax. Anyway you slice it or dice it, the ground system for Marconi-type antennas, such as verticals, is crucial. For the verticals that do work well, the operators all testify to the enormous amount of physical work requred to errect them. And this effort is unequally divided between installing the vertical element (easy) and constructing the ground radial system (hard). Again, most of the time you will spend in the field will be consumed by installing the ground system. There is a lot of talk in the community about using elevated-radials as a short-cut around putting in buried radial systems. As few as 2 elevated radials are said to be sufficient to extract some modicum of performance from a vertical. 4 elevated-radials are heralded as working as well as 32 buried radials. I think such observations might hold true when the vertical is installed near salt water. Yet, when installed inland, verticals with 2 or 4 elevated-radials did not work as commonly described. I had to get to 15 elevated-radials before the vertical started to behave in the field as it is supposed to on paper. And it took 15 elevated-radials before the signal reports I received started to approach those of fully-developed vertical systems.
So I thought it would be interesting for the reader to examine the various stages of the elevated-radial system I incorporated over a period of several months, as seen in the photographs below. Part of what is evidenced in this review is the progression of my own view about the ground system from an initial disregard for it, to an almost obsessive fixation for it. My take-away from all of this work is that the ground system is the aspect of the vertical antenna system which rewards hard work with improved performance. And when I think back on this realization, I cannot understand why it was not apparent to me at the beginning. This is because installing the vertical is not hard to accomplish. It's relatively straight-forward. And since there are no "free lunches" in antennas, to get the vertical to work as well as it is supposed to, additional labor had to be focussed on some other part of it. And that part turned out to be the ground system.
Our review starts with the photographs below depicting the full-sized vertical mounted to the back deck of the home QTH in early March. The same two elevated-radials used for portable operation at seaside locations are used as a coounterpoise for the full-sized vertical. That is the whole ground system at this point. Two elevated radials.
Two Elevated Radials • 1/4 Full-Sized Vertical • Symetrical Distribution
You can see the simple means used to connect the elevated-radials to the shield of the coax, consisting of a bolt mounted to the bottom of the PVC insulator. Nothing more than that is required. A wingnut is run down to tighten the electrical connection, as well as to enable the radials to be removed without any tools. A couple makeshift PVC poles are stuck into the (soggy) ground to support the ends of the radials. Aside from the mathematical miscalculations already covered--which cause difficulty in tuning the vertical--the signal reports received from on-air operation are disappointing. Not much power is being radiated by this set up.
So I relocate the vertical to the Test Range 150 feet behind the QTH in the woods. I double the number of elevated radials from 2 to 4. This lowers the vertical's feedpoint resistance. But the reports from DX stations are disappointing. And this is with 4 elevated radials! This is supposed to be equivalent to 32 buried radials, according to eHam chatter. No joy here. So I move on.
You can see that I have yet to develop respect for ohmic losses associated with the connection of the radials to the shield of the feedline. I simply kept stacking radial wires to the binding post at the bottom of the PVC insulator. And, of course, there is no effort to reduce common mode through use of ferrite beads. It got to the point where I could not run down the wingnut sufficiently to get a decent DC electrical connection, let alone a low-loss RF connection. Take a look at how messy this is.
Four Elevated Radials • West Vertical • Symetrical Distribution
I double the number of radials again, this time from 4 to 8. This is more than what the common literature calls for, and uses up the rest of the speaker wire in my junkbox. At this point I cannot stack the new wires on top of the old ones around the ground stud. I try it, anyway. At this point the lightbulb goes off in my head, providing the first glimmer of the eventual realization that the ground system is "where it is at", so to speak. So I add a circular ground bus wire to the grounding post. It is made of AWG #12 solid copper, and encircles the base of the vertical. Scraps of PVC lying about the work shop are recycled as stand-off insulators. The thing works. I can even remove it by pulling the PVC tubes off the PVC end-caps. I transfer all of the elevated radials thus far acquired over to this new contraption. I solder them with a propane torch. So far in this review, we have seen the system start with 2 elevated-radials. And then four. Now we are up to eight, with an improvement in the means of making the base connection.
Eight Elevated Radials • West Vertical • Non-symeterical Distribution
Although the feedpoint impedance gets closer and closer to 36 ohms, and the SWR/reactance curves continue to align themselves closer to textbook theory, even with 8 elevated radials the vertical's performance is not nearly where it should be. When calling CQ DX above 7175 Khz, I am getting responses from General class hams reporting that I am extremely loud. But the DX reports I seek still elude me. By this point my comparative reports are derived from daily contact with a group of Bulgarians on 7164 Khz, and by piggy-backing VE9ZY, Mac, who has taken an interest in the project. Mac runs a pair of phased verticals, each with 120 buried radials. We are both runing comparable power. But the difference in signal reports from DX stations--with mine being 30 to 40 dB lower than VE9ZY's--is tremendous, and cannot be attributed to Mac's forward gain or the near field efficiency of his buried radial system. A significant portion of the discrepancy is due to my inefficient ground system. I conclude that eight elevated radials are not enough to recover the ground losses encompassing the Test Range out in the woods.
#26 Enamel Magnet Wire • East Vertical • Non-symetrical Distribution
I randomly begin stringing radials in any direction that harbors an anchoring point, using AWG #26 enamel magnet wire because my speaker wire ran out. When I get up to around 18 elevated radials, things take a turn for the better. The feedpoint impedance is 36 ohms, and with the SB-221 input tuned circuits optimized for the exciter, I can now use the Murch transmatch between the amp's output and the feedline in the shack. This enables me to pump more power into the coax, which is showing a pretty hefty SWR at the transmitter end. None the less, DX signal reports are picking up. One special night Italian hams, who have been watching the project, excitedly advise me to "not touch a thing" for my signal is 20 dB over S-9 in Rome. It appears soldering the radials to the ground bus wire, and increasing them to 18 is stabilizing the system. The vertical is starting to behave as the textbooks predict. And the SB-221 finally sees a 50-ohm, non-reactive load via the Murch tuner. I make a mental note that the ground system is key to getting the vertical working correctly, and that I will be doing a lot of work on it during Phase III of this project. For now, however, the vertical is operating decently. And I can now spent cold, winter nights at the helm of a high-powered station working DX on 40 Meters from the sanctity of a New England workshop.
Moving this story about the ground system ahead at a faster clip, after getting the first (West) vertical operating with 18 elevated radials, I turn my attention to constructing the second (East) vertical. I applied the lesson learned on the first vertical to the installation of the second. I use a ground bus and #26 enameled magnet wire to string up about 15 elevated radials. I have yet to discover the error I have been making when calculating 1/4 wavelength on 40 meters, so I cannot get either vertical to resonate at the target frequency of 7150 Khz. The good news is that they resonate around the same frequency: 7450 Khz. The second (East) vertical goes together a lot easier, and looks a lot cleaner electrically in the end. Perhaps because of this, it's feedpoint impedance is a lot closer to 36 ohms than the first vertical. I make a mental note to clean up the rats nest of ground wires on the first vertical, making sure to use the same wire type when doing so.
Evolution of Ground Bus Ring
AWG #14 to AWG #6 Solid Copper Wire
Jumping ahead several months to conclude this story--I finally replaced the AWG #6 ground ring with one made out of 1/4" copper tubing (into which I inserted a AWG #6 solid wire to stiffen it up). I also increased the size of the ring terminals and associated connecting bolt.
Final Evolution of Ground Bus
AWG #6 Solid Wire to 1/4" Copper Tubing
The use of 1/4" (solid) copper tubing ended up creating a massive ground ring--the setails of which are described shortly. But let me digress by returning back to several months before its installation to describe the evolution of the elevated counterpoise system. After installing the AWG #6 copper ground bus, I then rip out all of the speaker wire and #26 enamel wire radials, and restring them with AWG #18 stranded copper wire ($33/500' @ Home Depot). This increases the DX signal reports I receive by about 15 dB. So there is a big lesson to be learned at this juncture of building the ground system for this pair of phased verticals. And that lesson is reduce the Ohmic losses throughout the elevated counterpoise system. First by SuperSizing the ground bus ring. And then reducing the resistivity of the counterpoise wires, themselves. Going from a single strand of #26 copper wire to stranded #18 copper wire made a huge difference. Probably the biggest difference of all the changes having been, and about to be, made to the array.
25 Elevated Counterpoise Wires • Symetric Distribution
AWG #18 Stranded off a AWG #6 Ground Bus Ring • DX Signal Reports Up 15 dB
When installing the #18 stranded copper radials, I measure each to the same length, +/- 1". Initially I string 15 per vertical. But then I went back and installed catenary lines around both verticals, which took about a week. I was then able to re-re-string the #18 radials, setting them out in a symeterical pattern from the bases of each vertical. And then I went back over the next 2 weeks and added more. I added insulators while so doing, and spaced all points of intersection with 6" PVC tubes.
Final Assembly • 30 Elevated Radials
1,500 Feet #18 AWG Copper Wire • End Insulators • Catenary Lines • 6" Spacing Between Counterpoise Systems
I ended up using 1,500 feet of AWG #18 stranded copper wire for 30 elevated radials per vertical. I then went through the several steps needed to resonate the phased vertical system, beginning with resonating each vertical +/- 5 Khz while the other was disconnected from its feedline. Then I did it again, this time while the other vertical had a 50 ohm non-reactive load (resistor) connected to its feedline. And then I did it a final time while both verticals were connected to their respective feedlines. To adjust the verticals to resonance, I had to unbolt the ground bus and pull the PVC stand-offs from their end caps.
Final Tuning of the Array
Ground Bus Loops Allow Access to Vertical • DX Reports up 5dB
In the end, I picked up between 20 to 25 dB in signal reports from DX stations--compared to when I started with 2 elevated radials. I accomplished this partly through a methodological, and, at times, stumbling development of the elevated counterpoise system, and partly through improving the efficiency & impedance matching of the feedline system. Additional increases were obtained by matching the exciter input with the SB-221 amplifier and tuning of the array's phase delay & impedance-matching lines. Removing the transmatch at the end, after obtaining a non-reactive 50-ohm impedance at the transmitter end in the shack, also assisted in system performance. Finally, final tuning of the two verticals after installation of the elevated counterpoise system added about 3 to 5 dB of the overall system gain. I suspect raising the phased vertical array from 4 meters to 8 meters above ground would further enhance performance, although I will leave that task for the end of the summer. Below are photographs depicting the phased verticals in their final form, although the photographs were taken before number of radials reached 30 per vertical.
The Completed Phased Vertical System
The Phase Verticals in June, 2016
How are they holding up after 1 month of operation?
Hidden Behind Shrubs
40 Meter phased verticals are enveloped by forest growth.
HOBBIT ENTRANCE • Let's go through and see what's in there.
DEBRIS PILES • Deritus had to be cleared during installation.
COHABITATION • A bird calmly eyes us, so acclaimated he is to our presence in his sanctuary.
EXPERIMENTAL PARASITIC DIRECTOR • Sited off the East end of the phased array to the Northeast.
LOADED • A 50 ohm resistor shunted across the feedpoint of the director.
HOBBIT TRAILS ABOUND • One of several paths trodden during construction.
HOBBITVILLE • Another Hobbit Path, this one leading to the West vertical.
The West & The East Verticals • As they appear after 1 month of non-maintenance.
Looking Back at the East Vertical from the West Vertical
Another look at the debris pile upon our exit of the Test Range.
Peering through at the home QTH from inside the Test Range
THIS SECTION IS PRESENTLY BEING COMPOSED & EDITED
How to Build the Verticals
A lot of people on-the-air have asked about how to construct the verticals using materials available at your local Home Depot store. Although a lot of this is conveyed in the photographs, let's go through the construction of the final prototype, and add in a couple footnotes about how to beef it up mechanically.
The two verticals are not guyed. They are supported by 4x4 posts set in concrete to which 2x4s are bolted. Two metal brackets are fastened into the top of the 2x4 which receive PVC rings acting as insulators for the aluminum tubes that pass through them. The 4x4 posts are 8' in length with about 2 feet set in the ground. 50 pound bags of Quickcrete, a fast-setting cement available at Home Depot, are poured around the posts after they have been set into the holes. Water is then drizzled over the cement over a period of about 10 minutes. In about an hour the cement is set. Before pouring the water, the 4x4 posts are made standing true with a carpenter's square.
Only a few implements are needed to set base supports for verticals.
THIS SECTION IS PRESENTLY BEING COMPOSED & EDITED
Wiring-up the Remote Switching Box
Our attention now focusses on electrical aspects of the phased vertical array, and the construction of its remote switching box.
Use of T-connectors simplifies implementation of the Christman phasing method
Two phased verticals (of the type described herein) can assume three directive states. For the sake of our discussion, we will call them East, West and Omni. These three states require two relays in the remote switching box: one to toggle East/West, and another for omnidirectional operation. We will leave for later consideration the question of whether or not to isolate coaxial shields, which requires more relays, and assume the all the shields are connected together, which simplifies the wiring of the remote switching box. In our example we will employ the Christman method of phasing.
Phased verticals exhibit directivity due to a difference in the phase of the signal exciting them. This holds true for transmit as well as on receive. It is caused by two things: (i) how far apart the verticals are from one another, and (ii) the lengths of the transmission lines connected to them. In the case of receive, the phase difference varies in accordance with the compass heading of the incoming signal. If it arrives at the front of the array, the phase difference adds the signal up, making it louder. If the signal arrives behind the array, the phase difference cancels the signal out, making it weaker. Gradations between the two extremes are distributed over the intervening compass headings. So how great are these two extremes? A signal arriving in front of the array is enhanced by a factor of two (3 dB), whereas a signal arriving behind the array is reduced by several orders of magnitude (20 - 30 dB). Thus two phased verticals do not exhibit much forward-gain since they only double the signal on transmit and receive. They do so over a wide swath (~120-degrees), after which radiation drops off precipitously towards the rear (180-degrees). So when you hear someone switching the directivity of a pair of phased verticals back and forth on the air, the great difference you hear is not due to the forward gain. It's due to the reward rejection of the antenna. A pair of phased verticals oriented East/West on the East coast of the USA enhances coverage of European, African and South American signals by about 3dB, while reducing stateside QRM and QRN by about 20 to 30 dB. Thus on a clear winter night, a pair of phased verticals can produce an astounding listening experience.
Phased verticals do not exhibit high forward-gain. On receive, the compass heading of the incoming signal determines the phase difference between the verticals. On transmit, the phase difference between the verticals determines the compass heading of the outgoing signal.
- INSERT FIGURE 1 -
In this section we will visualize how phase differences develop between the two verticals.
Einstein's Theory of Special Relativity depends on the use of something Einstein called "frames of reference", which play a key role in the thought experiments he used to explicate his theory. We'll use these "frames of reference" in our attempt to visualize phase differences between verticals. Before doing so, let's take a look at Einstein's use of this concept. In Einstein's case, he uses frames of reference to set up a thought experiment in which a person is standing at a train station at the moment a train passes by (very close to the speed of light). The first frame of reference he sets up is that of the person standing at the train station. He then introduces a second frame of reference in the form of a person who is sitting on the train passing by the station. He then introduces a simultaneous event in the form of two lightning bolts which strike the earth at the same time. He points out that the person standing at the train station would perceive the two lightning bolts as occurring at the same time, since these two bolts strike at equal distances from that person. But for the observer traveling on the train, his frame of reference is in motion relative to the person standing at the train station. And thus, for him, the light from one lightning bolt would arrive before that of the other lightning bolt--even though both bolts strike the earth at the same time.
Another example is to set up a frame of reference (at rest) by imagining a person standing in a field looking at a train track whyich passes perpendicular in front of him. And then imagine a train going by on that track which has a flat car on which two more people are playing catch--throwing a baseball back and forth. So in this example we have set up three frames of reference. One os the person standing in the field watching the flat car going by. Einstein would call hius frame of reference "at rest". And two more frames of reference in the form of the two people standing on the flat car playing catch. Einstein would identify their frames of reference as being "in motion" relative to the person standing in the field. And would also identify their framnes of reference being "at rest" relative to one another.
So in this example, the person in the field wtaches the flat car pass by as the two other people throw the baseball back and forth. From his frame of reference, the time it takes the baseball to travel from person to the other as it is being thrown back and forth is not the same--eventhough for the people playing catch on the moving flatcar it is the same. For the person standing in the field, it takes the baseball a little longer to make it from one person to the other person when its direction of travel is the same as that of the moving flatcar. And that's because after the basebeall is thrown, it has to travel towards a glove which, itself, is being moved away from the ball by the movement of the flat car. So it takes a little bit longer to reach the glove. And when the ball is thrown back, as soon as it is thrown it travels towards a glove which, itself, is being moved towards the ball by the motion of the flar car. In this case it takes less time to pass between the two gloves. In other words, as soon as it is thrown, the person who is going tio be catching the ball is moved towards the ball by the motion of the flar car. In this case it takes less time for the ball to get to the person who catches it. All of this occurs in accordance with observations made from the first frame of reference--from the perspective of the person standing still in the field watching the train go by. At the same time, from the frames of reference of the two people playing catch on the flat car, the ball takes the same amount of time to pass between them.
The interesting thing is that you can take a stop watch and measure the time discrepancies that are produced in the different frames of reference.
because the speed of the flat car. baseball differsthrowithe light from the lightning bolt would reach him before the light of the other lightning bolt. a second person who was on the trainthe speed of light). train station hought experiment thought experiment , one important thought experiment these frames of reference The two sources of delay are (i) the spacing between the verticals and the transmission line lengths. Both produce delays based on how long it takes the signal to travel. In the case of spatial delay, varying the distance between the verticals varies the phase difference between them. Since in our case we are separating the verticals by 1/4 wavelength, the amount of time it takes the signal to travel between the verticals is equal to 1/4 of its 360-degree oscillation--or 90-degrees. 1/2 wavelength spacing results in a 180-degree phase difference. 3/4 wavelength spacing produces a 270-degree phase difference. The various phase differences, in turn, produce different directivity patterns. So if we want to change the directivity pattern by spatial delay, we have to change the spacing between the verticals. Since this is impractical to do, we focus on the other source of delay; namely, the lengths of the transmission lines. Changing the lengths of the transmission lines is a lot easier than changing the spacing between the verticals. One way to do it is to add a length of transmission line to either feedline. This can be done by means of a remote relay in the field.
When we add 1/4 wavelength of transmission line into either feedline, we add an additional 90-degrees of delay to one vertical, but not to the other. This causes the two verticals to be 90-degrees out of phase with each other to begin with--before we even take into account the delay caused by the time it takes the signal to travel from one vertical to the other. It also introduces the concept of a vertical "lagging" behind the other, since only one vertical has the extra transmission line connected to it. Finally, this arrangement radically alters the directive pattern of the type of phased verticals we are experimenting with. Let's run through what all this means.
The vertical that has the extra transmission line connected to its feedline is referred to as "lagging" behind the other vertical. And as things turn out, it is also the vertical consituting the front of the array--the forward lobe radiates off its end. The directive pattern, itself, assumes a cardoid shape.
Steering the Array: Line Delay & Space Delay
The phase difference can be varied by means of electrical wizardry. The Christman method, amongst others, accomplishes this feat by adding an extra piece of transmission lines to one of the vertical's feedlines. This compells the transmitted signal to take a little more time to reach one vertical compared to the other, and is called the "line-delay". It constitutes a part of the total phase difference between the two verticals. The other part is derived by how long it takes the signal to travel from one vertical to the other vertical, and is determined by the distance between the verticals. Both are expresed as degrees of the signal's oscillation.
Since the purpose of the extra piece of feedline is to delay the signal, it is called a "delay line". It's length is measured by the number of degrees the signal advances in oone of its oscillations during the time it takes to travel down the delay line. Interestingly, delay lines are measured in units of time, not distance. And these units of time, in turn, are not measured in seconds, but in degrees of a 360-degree oscillation. Since our array requires a 90-degree phase-shift, the length of our delay cable will be equal to how far the signal travels down this cable while it progresses 90-degrees, or 1/4, of an oscillation. As you might suspect, the 90-degree delay line ends up being 1/4 wavelength long. Equally uninspiring might be the realization that a "180-degree delay line" is 1/2 wavelength long, and that a "270-degree delay line" is 3/4 wavelength long. And, yes, we do have to take into account the velocity factor--but not until we are finished with all the theoretical calculations. In other words, don't even think about the velocity factor until you find yourself in the field with the wire cutters in your hand.
How phased verticals work is a little more complicated than this. And we will get into these details in a moment. For now, let this explanation suffice on our initial attempt to understand how this fascinating aerial works.
Cutting Delay Lines: Some Practical Tips
It is important to get into the habit of thinking of distance in terms of time when discussing phased arrays. You will find this to be true whenever delay lines, feedlines and inter-element spacings are discussed amongst afficinados. These phased-array experts appear to think of space as time measured not in seconds, but in the number of degrees a signal advances in an oscillation as it moves through space. This type of thinking transposes one-wavelength into 360 degrees, 1/2 wavelength into 180 degrees, and a 1/4 wavelength into 90 degrees. I reiterate this point due to the following quandary: what happens if you need an 84-degree line? Or a 71-degree line? How many feet is that?
To answer this question, let's suppose you're assisting an RF engineer constructing a phased array in the field. And he or she asks you to cut an 84-degree line of coax. What do you do? One approach is to reformulate the request as meaning they want you to cut off part of a 1-wavelength cable, which you know is 360 degrees "long". And that the engineer wants 84 degrees of it--or "84 parts out of 360". So, you divide 84 by 360 (on your iPhone) and get .2334. And then you calculate how long 1-wavelength is in feet (936/f), and multiply this by .2334. This gives you the length of the "84-degree cable" the engineer wants you to cut. After measuring it out on the ground, you hover over it with your wire-cutters. But then you abruptly stop. Why? Because you remembered to figure in the velocity factor!
Actually, you don't have to do that if you have an antenna analyzer. You can go ahead and cut the coax because the velocity factor, which Einstein would agree is always less than 1, guarantees the final length will be less than the amount you've measured out. After snipping off this length of transmission line, you can trim it to the precise "84-degree length" using an antenna analyzer, as covered elsewhere in this tome. How much will you end up trimming off? If the velocity factor is .82, which it oftentimes is, about 1/5th of the coax will be trimmed away. For a velocity factor of .66, it'll be about 1/3. If you don't have an antenna analyzer, now's the time to apply the velocity factor and make the final cut, adding on a couple of extra inches in case you screw-up putting on the connectors. Done. Close enough for government work.
Wiring the Remote Box
Remembering the shields are all tied together, let's examine how to wire up the remote relay box used to switch the directivity of the array, as provided in Figure 2, below.
One major aspect of the Christman phasing method is that it doesn't use a 90-degree delay line. Instead, a 71-degree delay line is used in conjunction with two, 84-degree feedlines connected from the switching box to either vertical. This technique produces the 90-degree phase difference required by the aerial while also forcing the currents fed to the feedpoints of the verticals to be equal. Now, it is at this point that our discussion about phased verticals will delve into some finer details about their operations. If you don't understand it, don't worry. Just re-join this review a few paragraphs down. Having said that, the reason why the Christman method uses such weird cable lengths to achieve the 90-degree phase shift and equal current distribution between verticals required for this system to work is due to the fact that each vertical, when it radiates its signal, induces a current in the other vertical. The two play off one another through the same mutual coupling found at work in a parasitic array. So when one vertical radiates as energy the current fed to it by the transmission line, it induces a current in the other vertical, which then re-radiates this energy resulting in another current being induced in the first vertical. And vice-versa. It all gets quite complicated, requiring the kind of complicated mathematics thankfully consigned to theoretical physics. The bottomline for our review is this: although equal currents are forced at the feedpoints of both verticals by Christman's odd cable combinations, the two verticals do not end up radiating equal amounts of energy. Some of the energy radiated by one vertical is coming from the other vertical. If it was not this way then feeding two verticals would only result in twice the effected radiated power produced by a single vertical. And this is, in fact, what we do see happening in the "forward" direction of two phased verticals--a 3 dB increase in the radiated energy. But this doubling of the radiation off the "forward" end of the array is not the result of all the complicated interactions between the two verticals due to mutual coupling and phase differences. These aspects of the array are what cause the tremendous reduction of radiation to its "rear". The complicated interactions of currents inducing other currents due to the mutual coupling between the verticals causes the huge rear null in the array's radiation pattern. This is the product of these complexities--not the 3 dB of forward gain. The 3 dB of forward gain is a side-product of the fact that the energy not being radiated by the rear of the array has to go somewhere; it can't disappear. It's spill-over. The physical analogy can be approximated by imagining sticking your finger (deeply) into a party balloon: one side becomes conically depressed as the other side slightly expands.
And you can tell which is the primary result and which is a concomitant of all the complicated current interactions between two phased verticals by comparing the essence of the rearward null to the slight forward enhancement. The rearward null has the more pronounced essence in the form of reduced radiation several orders in magnitude dispersed over a well-defiined, sharp angular displacement. Compare that to an almost imperceivable 3 dB doubling of radiation dispersed over a wide, 120-degree swath. Which is the result of the complicated current interactions dictated by phase differentials between two verticals, and which one is the result of the fact that radiation displaced by the former has to end up somewhere? One way to intuit an understanding is to imagine the complex current interactions between the verticals causing a doubling of radiation over 120 degrees on one side of the array, causing the displacement of several orders of magnitude of radiation over well-defined, sharp angles on the other side.
Use of T-connectors to link the 84, 71 and 84-degree cables to each other (in that order) simplifies the wiring of the remote switching box, to which the T-connectors are attached by means of SO-239 connectors. This arrangement enables the 71-degree delay line to be neatly coiled and hung off the remote relay box which, itself, is mounted between the two verticals.
When the remote switching relay connects the main feedline to the first T-connector, the first vertical gets fed through its 84-degree line while the second vertical gets fed through its 71 and 84-degree lines. This causes the signal radiated by the second vertical to lag behind the signal radiated by the first. When the relay connects the main feedline to the second T-connector, the second vertical is now being fed through its 84-degree line while the first vertical is being fed through its 71 and 84-degree lines. This causes the signal radiated by the first vertical to lag behind the second vertical. This reverses the directivity of the array--which beams towards the vertical that has the extra coax in its feedline.
Construction Tip: Wire up your remote switching box so that the extra coax is added to the vertical pointing towards the DX region you work most. This will cause the phased array to point in this direction when there is no power sent to the remote relay box.
A second relay shorts out the 71-degree delay line, causing both verticals to be fed through 84-degree lines. This causes them to radiate in phase, which produces the omnidirectional pattern.
Whether or Not to Isolate the Elevated Radials
At some point you need to decide whether or not to tie the elevated radial systems together wherever they intersect. You can wrap wires or solder them at their intersecting points, or electrically isolate them with insulated spacers. I opted to isolate them with 6" PVC spacers because a footnote I read in a technical paper indicated that doing so adds about .75 dB to the array's forward gain.
Keeping the elevated radial systems electrically isolated necessitates lifting the shields of the coaxial cables at the switching box. This, in turn, requires relays to switch the shields along with their respective center-conductors in accordance with the various configurations just described. Using a plastic box isolates the SO-239 connectors. However, if you use a plastic box in a system that ties the shields together, grounding the SO-239 connectors with a piece of wire introduces a reactive component which degrades the array's performance. The workaround is to either (i) ground the SO-239 connectors with a copper or aluminum strap, or (ii) use a metalic box for the remote relay enclosure.
Purists can employ plastic boxes in which relays switch coaxial shields along with center-conductors. If you are using low-power, a single DPDT relay can be tasked to switch the array's directivity East-West, and another DPDT used to short out the delay line as described. For higher power ooperations it might be advisible to double-up the contacts of a DPDT relay to increase it's power handling capabilities. If you opt for this approach, you will need two (2) DPDT relays with the shields all tied together, and four (4) DPDT relays for the ground-isolated configuration.
UPDATE: October 17 - 24:
Fattening Up the Phased Verticals for Winter
Increasing efficiency by reducing ohmic losses
1/4" Copper Tubing Grounding Rings
A scrap of 2x4 mocks-up the center support, enabling us to figure out the correct dimensions for the stand-off insulators.
Disassembling & Cleaning the Vertical Elements
Antenna work continues with the reduction of ohmic losses in the phased verticals. First up is the dismantling of the vertical elements so that their joints can be cleaned and treated with an anti-oxidant grease. Upon reassembly, the "slit/hose-clamp" method will be used to secure the joints, instead of the original sheet metal screw.
Day #1: Cleaning the East Vertical
Despite the thickly wooded area, bringing down a vertical is a fairly straightforward process.
Once we open up the patient, we can see that the junctions are in need of a good cleaning (Brasso), followed by some anti-oxidizing grease.
After cutting a slit in the outer section, the junction is secured with a hose clamp.
New Grounding Rings
Second up is the reconstruction of grounding rings out of 1/4" copper tubing through which a #6 solid copper wire is inserted to stiffen it up. After the counterpoise wires are soldered to the rings, the contraptions will be sprayed with Liquid Electrical Tape. The cleaning of the verticals's junctions, and beefing up of their grounding rings, should reduce ohmic losses and enhance overall efficiency. Upon reinstallation the system height will be increased from 4 meters to 6 meters over the ground.
Devising New Grounding Rings in the Workshop
Trial and error, combined with precise measurements and cup of coffee, brings forth the new design. On the right is the connection point for the feedline shield.
Before & After
On the left is an old grounding ring made out of AWG #6 solid copper wire. On the right is a new one made out of 1/4" copper tubing with a #6 solid wire inserted to stiffen it up.
The stainless steel eyebolts enable the counterpoise wires to be soldered with a torch without melting the PVC tubing.
Ring terminals secure the ends of the copper ring around the ground stud, which has been increased from 1/4" to 5/8".
Hard at Work
The workshop remains a mess over the several days needed to complete this antenna clean-up.
DAY #2 & #3
Cleaning the West Vertical & Installing the First Grounding Ring
Day #2 involved cleaning the West vertical, which went without a snag. On Day #3 the first grounding ring snapped perfectly into place beneath the East vertical. I lost light before being able to solder the counterpoise wires to the grounding ring, so I left them twisted.
New Grounding Ring Installed in East Vertical
Ring snapped into place perfectly. Counterpoise wires migrated easily. Significant increase in system efficiency noted back in the shack.
Each wire was cleaned (with Brasso) before being transferred to new grounding ring. Everything is in good shape for continuation of the job tomorrow, which will begin by stringing more counterpoise wires before soldering and sealing up the ring. Back in the shack the results were immediately evident. The amplifier loads more fully. Looking forward to continuation of the install tomorrow.
Installing the Second Grounding Ring on the West Vertical
The fourth day marked the completion of installing the grounding rings, with the second one fitting perfectly into the West vertical. The counterpoise wires were transferred over in the same manner as had been done the previous day at the East vertical. I lost light again, so was unable to solder any of these connections.
New Grounding Ring Installed in West Vertical
Ring snapped into place perfectly. Counterpoise wires migrated easily. All ready to be soldered with a torch tomorrow.
When I returned to the shack, the amplifier loaded up even more fully than the previous day. I also perceive some of the computer hash QRM plaguing the phased verticals on receive is diminished, although more time is needed to confirm this observational supposition. On-air testing produced incredible reports from stateside and European stations. Cleaning the vertical system appears to be producing overall improvement to the system's efficiency. We'll see more tomorrow when we solder the base rings up and weatherproof them with Liquid Electrical Tape.
On the sixth day I awake at dawn with the excitement of knowing that today will complete the job of sprucing-up of the verticals. I prepare the toolkit while sipping coffee in the workshop listening to Pacific stations on the West Beverage. Once geared up, I head out to the Test Range which is illuminated by a light which sets the verticals off against their bucolic background. I return to the workshop and retrieve the camera in order to shoot some photographs of the verticals before beginning work on them.
West Vertical Awaits Soldering in Early Morning Light
I apply rosin flux to the connections on the West vertical and light up the Butane torch. Unfortunately, it's tip is clogged with solder from similar work performed on a Moxon in Boston years ago, so the flame it emits is yellow and sputters. I cannot solder with this tip, so I return to the workshop and rumage through an old toolbox where I believe I might have another torch tip. I do! Purrfect. I return to the site and replace the clogged one with it. Once sparked by my Zippo, the torch roars like the afterburner on an F-16. I adjust the thumbscrew until the blue-flame tip approximates that found on a Sharpie marker pen, and then climb the ladder up to the base of the West vertical. Despite the heavy gusts, I am able to work my way around the ring loading solder into each connection as the flux bubbles on the next. I am surprised at how quickly I am able to dispatch the job. Shutting the torch off, I climb down and, like a proud parent, pick up my camera. Twins.
Soldering Complete in West Vertical
Grounding ring connections soldered with butane torch • Next-up: Liquid Electrical Tape
I shuffle through the toolkit and retrieve a ZipLoc bag containing a wetted microfiber towel. I climb back up the ladder and clean the resin off the grounding ring. I then dry the ring with a second towel. Back down the ladder and another sifting through the tool bag produces my trusty bottle of Liquid Electrical Tape. I climb back up noting to myself how easy these last few stages of the job are compared to all the work required to get here. I carefully apply the Liquid Electrical Tape reminding myself several times to not skimp on the material, nor worry about having to buy another bottle. After putting on the initial first-coat, I climb down the ladder--happy that all I have left to do is brightwork--such as applying the second coat and installing the ferrite beads that on their way right now from The Wireman. All the heavy-lifting is done. I move over to the East vertical and perform the same tasks, thinking all the while of how far I have come since that blustery day last March pushing the 50 Lb. bag of cement and the post-hole digger in the wheelbarrow in the snow.
Here are some photos documenting this work, beginning with the West vertical.
THE COMPLETED WEST VERTICAL
THE COMPLETED EAST VERTICAL
UPDATE: October 8:
Phased Verticals Modelled
4.95 dBd Forward Gain, 14-degree Take-off Angle
Modelled by G3ODO/W4
W1ZY's Vertical & Horizontal Patterns
Calculated by G3ODO/W4 using EZENEC-5
I want to thank William Buckett, G3ODO/W4, for taking the time to model The Gadget at his well-mulched laboratory in Georgia. The recordings below bear witness to Mr. Buckett's modelling. The first depicts 7 Mhz transatlantic communication at 3 PM in the afternoon, arguably demonstrating the low-angle component predicted by Buckett's model.
Working Europe at 3 PM
QSO with ON4AYM in Belgium at 3 PM local time (1900 UTC) • Kenwood TS-520
Transmitting on elevated phased verticals. Receiving on a NE Beverage. Automatic changeover implemented.
The second recording superbly demonstrates Bucketts's horizontal plot by conveying the array's front-to-back response when excited by a signal eminating from East Africa. The signal is purportly that of Ethiopia jamming Eritrea on 7175. These efforts by Ethiopian officials enable us to check the front-to-back ratio of the phased verticals which are sited almost due East/West, and optimized for 7150 Khz. It is hoped these recordings and William Buckett's plots encourage other hams to experiment with phased verticals at their QTHs.
Monsterous F/B Exhibited by Phased Verticals on Receive
Ethiopian Government Jamming Signal • Recorded on 7175 Khz at 0200Z • Early-October, 2016 • Kenwood TS-520
UPDATE: OCTOBER 7
Beverage Terminating Resistors Now Available on eBay
With mounting bracket, multiple surge suppressors & spare Ohmite resistor
Beverage Termination Resistor
Mounts to ground rod. Capsule opens to service 2-watt Ohmite metal-ceramic resistor & Bourns 90V GDT.
Spare cartridge without bracket
UPDATE: SEPTEMBER 24
The 1/2-Wavelength Suburban Beverage
A Short 40 Meter Beverage Eliminates Plasma & Computer Hash on Receive
Ever since I put up the elevated phased verticals last Spring, I have been struggling to hear weaker signals through a noise floor I assumed was cosmic. Turns out it wasn't. Turns out the elevated verticals are susceptible to local hash pouring out of consumer electronics, garage door-openers, cheap laptops, "wireless" dog fences and every plasma TV in the neighborhood. These sources produce a white-noise-birdie-hash-floor blanketing signals below S-7. This is why I have been struggling to copy Europeans running 100 watts or less on low dipoles for the past several months.
A Short Beverage for the Suburbs
At only 1/2 wavelength, the aerial may not have much directivity. But it does eliminate local hash in suburban environments.
And it's forward lobe closely matches that of the phased verticals, producing complimentary coverage.
Comparison Between Phased Verticals & 1/2 Wavelength Beverage
7Z1RR in Saudi Arabia • 7140 Khz • October 1, 2016 • 0330 UTC • Kenwood TS-520
Since I never used a vertical before, I assumed they are noisy on receive. The recording below demonstrates this by comparing a 2-wavelength Beverage to the phased verticals while both are pointed West at 8 AM in the morning.
Beverage Eliminates Local Noise & QRM
290' Pacific Beverage vs. Phased Verticals (West) • 7005 Khz • October 11, 2016 • 1200 UTC • Kenwood TS-520
Short Beverage Construction Notes
Given my space limitations to the Northeast, the best I could do was install a 1/2 wavelength Beverage up 8 feet off the east-end of the phased verticals. A matching transformer consisting of 5-turns of #26 enamel wire (secondary) and two turns of #22 insulated hook-up wire (primary - 75-ohms) was wound on a binocular ferrite core. When loaded by a 470 ohm non-inductive resistor, it exhibited 78-ohms from 1.8 Mhz to 21 Mhz. I temporarily housed it in a weather-proof box easily opened in case I blow it out by accidentially transmitting into it.
Beverage Feedpoint Tuning Box
Used for tuning Beverages. Black carbon deposits are from accidentially transmitting into the Beverage.
After tuning the Beverage, I installed the matching transformer into a cartridge fitted with an SO-239 connector. I built two. If one fails in the field it can be replaced with the other one.
Beverage Matching Transformer & 90 Volt Bourns Gas Discharge Tubes (GDT)
Replaces tuning box at feedpoint. Mounts to ground rod. Matches 450 ohms to 75 ohms.
Lightning surge protected by Bourns 90v GDT and external spark gap.
The Perfect Rainy Night
Reception of the Spanish special-events station AN400T, as heard in the recording below, constitutes a great example of listening to DX on a short Beverage. Because the operator was working his pile-up by numbers, the 5-minute recording affords the opportunity to sample signals from regions not favored by the NE Beverage. Interestingly, at 02:16 in the recording the receiver is switched to the phased verticals, as annoted in the video, which are then alternated between East and West (until 02:28) to enhance reception of a station in the American midwest. This occurs again at 03:05, and again at 03:55, in the recording to check the F/B of the short Beverage by comparing it to the phased verticals on stations in South America. It is hoped this recording demonstrates to hams operating from limited spaces the enhanced DX reception possible from a short Beverage.
Listen to AN400T on the 1/2 Wavelength Suburban Beverage
AN400T in Spain • 7140 Khz • October 1, 2016 • 0200 UTC • Kenwood TS-520
Terminating the Beverage
In the beginning, I merely attached a resistor to a ring-terminal and screwed it into the ground rod--which in my case is a copper pipe. This enables me to change the value of the resistor while tuning the Beverage with the MFJ 259B antenna analyzer.
2-watt Ohmite Metal-Ceramic Terminating Resistor
Straightforward mechanical attachment used during tuning phase
After getting the Beverage tuned, I placed the resistor in a capsule similar to that used for the matching transformer. I made a spare so that replacing a bad terminating resistor is reduced to merely snapping in a new cartridge. Back at the shack, the old one can be opened up and refurbished. To forestall such routine maintenance, I doubled-down on lightning surge suppression; in addition to a 90 Volt Bourns Gas Discharge Tube (GDT) shunting the antenna terminal to ground, I added the external spark gap jumper suggested by W8JI. I made a bunch of these things and put them on Ebay for hams who asked for them.
Beverage Terminating Resistor
Mounts to ground rod. Opens to replace resistor & GDT.
Tuning the Thing
To tune the aerial, Tom, W8JI, suggests using an antenna analyzer to seek minimum SWR fluctuation over a frequency sweep 4-times higher than the targeted frequency (http://www.w8ji.com/beverages.htm). If grounding at both ends has been stablized, adjusting the value of the terminating resistor should lead to the maximization of the aerial's F/B ratio. In our case, the initial sweep from 1.8 Mhz to 21 Mhz with a 470 ohm terminating resistor caused the SWR to fluctuate between 1 : 1 to 2 : 1 about every 3 megacycles. Lowering the terminating resistor to 220 ohms increased both the extent of the SWR range, as well as the frequency with which it fluctuated. It was assumed that the higher terminating resistor value of 470 ohms produced better results than the lower resistance, and that further work on the ground system was the best way to procede.
Copper Pipes as Ground Rods: Cleaned with Brasso Before Being Driven into the Soil
The quick rub-down does little to improve conductivity, but makes for a great photograph in articles like this.
After installing three (15') radials at the far end, and two at the feed point, the same sweep with the 220 ohm terminating resistor showed 84 ohms resistance, and the SWR fluctuating between 1.8 : 1 to 2.4 : 1 (over 7 Mhz to 21 Mhz). I then removed the matching transformer and re-wound it. I found that by doubling the number of "turns" suggested on the W0BTU web site, the analyzer showed a more broadbanded 72-ohm response. So I replaced the transformer at the feedpoint and performed another sweep with a 470 ohm terminating resistor connected at the far-end of the antenna. When swept from 7 Mhz to 21 Mhz, the SWR fluctuated between 1.0 : 1 and 1.6 : 1 every 2 Mhz. At 7150 Khz, the SWR was 1.4 :1, which I interpreted as an SWR of 1 : 1 since I was using an instrument with a 50-ohm input impedance to measure the SWR of a 73-ohm, essentially non-reactive load. Done.
MFJ 259B Final Readings (left) at Northeast Beverage Feedpoint (right)
A perfect match with a 73-ohm input impedance and 3-ohm reactive component.
Old Timers Tell Me to "Keep (My) Hands Off Those Phased Verticals" This Fall
In response to my admission of harboring a desire to tweak the elevated phased verticals this Fall, several old timers implored me to "keep (my) hands off those verticals", telling me that I would "screw them up" if I "horse(d) around with them any more". Since the only thing these old timers know better than antennas is me, I am taking their advice to heart and (re)focussing my efforts this Autumn on improving the receive system. The strategy is to optimize the short NE Beverage, then "screw it up" by trying to make it into a "two-wire" reversible affair. If I get that far, then build a second one staggered alongside the first. These will be pointed at Europe/South America. To enhance reception of Pacific signals, a 290' Beverage has just been run to the West.
Terminated End of 290' Pacific Beverage
Terminating resistor mounted on ground rod. Radials yet to be installed.
Baseball (with mason line attached via lag bolt) enabled wire to be run-out above underbrush.
All this requires multiple runs of RG-6 coax to the woods--one line of which having already been laid. And some kind of system to manage these receiving antennas has to be devised for the shack.
TS-520 Modification: Antenna Select Switch
I am already working on this. My solution is to modify the TS-520 by converting its antiquated "Channel Select" switch into an "Antenna Select" switch to choose between four (4) different receive antennas--or three plus the transmit antenna. The switch will energize relays that connect different receive antennas to the receiver's input. Since this all happens upstream of the rig's T/R relay, there is no possibility of accidentially transmitting into any of the receive antennas. To prevent RF ingress during transmit, the receiver input is lifted and the receive antennas are grounded. The system is powered from a 12 volt bus on the rack above the receive antenna panel, as seen below.
Modifying the TS-520 for Receive Antennas
Converts the "Channel Select" switch into an "Antenna Select" switch.
Depicted above in prototype form (left), along with the receive antenna input panel (under construction; right).
I have the switch programmed to select either the transmit antenna, position #1 (phased verticals), or the Beverages, position #2. The "XVerter In" phono jack on the back of the TS-520 has been re-tasked as an "External Ant In" jack. So when I switch to position #2 the rig receives off of whatever antenna is plugged into this phono jack--albeit via a relay which lifts the receiver input off this jack to reduce RF ingress on transmit. This jack, through a phono plug & cable, is connected to the external receive antenna panel bolted into the rack at the operating position, as seen above, where the two Beverages are connected. Each is routed through a relay which, when off, grounds the antenna. When it is on, the antenna is connected to the "External Ant In" jack on the back of the TS-520. The switch actuating the two relays is mounted beneath the switch that controls the directivity of the phased verticals. Thus all antenna directivity switches are grouped together. .
- More to follow -
October 16, 2016
Here's what I ended up with.
Receive Antenna Input Panel & Directivity Switches
Beverages are connected to the receive antenna input panel (left) and selected by toggle switch with illuminating lamps.
Below the Beverage switch is a second switch which controls the directivity of the phased verticals.
Here's How It Works
PY2ZZ Working Stateside • October 18, 2016 • 40 Meters
Demonstrates use of multiple receive antennas
From this recording we can begin to see the system paying dividends. We also see that neither Beverage affords coverage to the South, indicating each exhibits decent F/B and/or side rejection. After setting the phased verticals to the East, and the Beverage to the West, alternating between the two is reduced to flipping the modified switch on the TS-520.
UPDATE: October 14:
Comparing the Directive Patterns of the Northeast & Pacific Beverages
The Northeast Beverage: Done
Tuning of the Northeast Beverage shows 73-ohms of input impedance with a 3-ohm reactance component. Done.
75-ohm Match on Northeast Beverage
MFJ-259B shows 73-ohm input impedance and a 3-ohm reactive component at the feedpoint of the Northeast Beverage.
SWR fluctuates 1:1 to 1.6 : 1 every 2 Mhz. from 1.8 to 21 Mhz.
Attention now focusses on tuning the 290' Pacific Beverage. It already is receiving well, as heard in a couple of recordings below. With the installation of the first 2 ground radials at the feedpoint, the F/B appears to have diminished. More work underway. A few days after posting this, I ran two ground radials at the far end. This increased the F/B. More radials will be laid on the far end. It is rather slow going due to the heavy briar undergrowth, though.
290' Pacific Beverage
Feedpoint matching transformer (left) and far-end terminating resistor (right).
Initial sweep shows SWR fluctuatting between 1:1 to 2:1 every 2.5 Mhz (from 1.8 to 21 Mhz).
Comparing the Northeast & Pacific Beverages on a Stateside Signal
Toggling between the Northeast and Pacific Beverages while listening to N4YDU • October 13, 2016 • Kenwood TS-520
Testing the New Pacific Beverage: VK3SS in the Early Morning
VK3SS at 7:30 AM EDST • Transmitting on phased verticals • Receiving on the Pacific Beverage • Automatic changeover
7155 Khz • October 13, 2016 • Kenwood TS-520
UPDATE: AUGUST 18:
Portable Saltwater Vertical Operation • 2200 - 0100 GMT • YouTube coverage below!
Last night we enjoyed an extended EU pile-up between 0400 to 0530 GMT from the Point Judith location under a beautiful full-moon. Below are some of the YouTube coverage this garnered from both sides of the Atlantic. Check out the DX signal strengths on the saltwater vertical!
Hear the Saltwater Vertical in Europe
August 18, 2016
Listen to Signals on the Saltwater Vertical
August 18, 2016
Some interesting observations:
Thanks to 2E0KDT/M, CT1HFS and WA3FET for making the recordings. More oceanside operation will be attempted between 2300 and 0500 Z as time permits.
UPDATE: AUGUST 21:
Does Putting Land in the Vertical's Far-field Reduce Its DX Signal?
Results: Inconclusive. But during the experiment, the Saltwater Vertical unexpectedly busts the VI6 pile-up longpath with 80 Watts. And then does it again for the YouTube video!
The Saltwater Vertical Installed at the Matunuck Point Location in August, 2016.
THE EXPERIMENT: To see what happens to the vertical's signal in Europe when you put land in its far-field path to Europe. On the afternoon of August 20, 2016, we set up the portable vertical at the second location, Matunuck Point, which faces South. This causes the vertical to have a clear shot over saltwater to the West, South and East. The far-field of the vertical's northeast path to Europe, however, is now over land. The map below shows how the relation between the first and second locations causes this to be the case.
The Two Test Sites Afford Different Far-Fields to Europe
Preliminary Results: European "Beacon" Signals Appear Attenuated
The map to the left is extremely blown up in the map to the right. The distance between the two test sites is approximately 3 miles. At Location #2, the Northeast path to Europe is over land, in contradistinction to Location #1. So what did we find out? Well, conditions to Europe were not wildly open over the operating window (2230 - 0200Z), but we did work three stations which are regularly worked from the first location. UR5VFS and UT7HA--who are about 20 KM apart from one another--and CT1EHI in Portugal. The very non-scientific observation is that UR5VFS and UT7HA were between 10 to 20 dB down compared to their normalized signal strengths at Location #1. CT1EHI's signal was down 10 dB compared to its early reception on the phased verticals. Marco was 59 at 2230Z, or 5:30 PM local time, and devoid of QSB. Interestingly, during the EU pile-up a few days earlier, several EU stations remarked that our transmitted signal had no QSB. I don't know what either means, but it is what was observed in the field. Obviously we need to do this experiment again. The best way would be to operate two of the verticals at the same time from the two locations.
Construction Note: Detail of PVC Base Insulator & SWR-adjustment coil.
The metal mounting brackets lift the insulator off the post, allowing the SWR-adjustment coil to slide freely.
This allows adjustment of the SWR at the different locations, which alleviates need for a tuner.
Saltwater Vertical Breaks VI6BLT50 Longpath Pile-Up Twice
The excitement was the huge pile-up that developed on 7135 Khz, starting at about 2300Z, on VI6BLT50--the Wireless Institute of Australia special commemerative operation presently working portable from Sydney. On 40 they are using a four-square vertical array. They were coming in 59+10dB. The pile-up was LONGPATH for North and South American stations, and (presumably) short-path for the European stations. I was surprised to break the pile-up with 80 watts on the first call. I then did it again for the sake of the YouTube seen below. Check out VI6BLT50's signal strength and its lack of deep QSB dives, as well as how many inland North American stations require several calls. Such observations arguably evidence through non-scientific means what happens when you get an antenna's take-off angle down to 1 or 2 degrees.
Watch the Saltwater Vertical Bust the VI6BLT50 Longpath Pile-up
(Followed by extended reception of the pile-up)
August 21, 2016
"Enhancements to increase an inland station's effective radiated power--from amplifiers to high towers to stacked arrays--
are man-made attempts to recoup the lower path losses afforded by ultra-low take-off angles."
-- Bill DesJardins, W1ZY
COOL IDEA: Varying the Distance of the Vertical to the Ocean Without Moving the Vertical
Variations in the vertical's SWR were observed as a function of the tide, a phenomenon exasperated by the topography of the second location where a 300' shelf is exposed at low-tide. This causes the seawater plane to be 300' away from the vertical at low-tide, and about 3 feet from the vertical at high tide
The Saltwater Vertical at Low-tide
The seaweed along the beach is the high-tide waterline. The surf way out at sea is the low-tide mark. Between the two is the 300' shelf which swamps twice per day.
As the tide rises it reaches a point where the Atlantic Ocean literally spills over the shelf after which it takes about fifteen minutes to reach the vertical. This extreme topography causes the tide to vary both the vertical's SWR and its distance from the ocean. It would be interesting to see whether or not such tidal flooding affects the vertical's radiation pattern in accordance with the animated gif below.
Salt Water Extends a Vertical's Low-Angle Lobe
To the left, the vertical over land. To the right, the vertical as it is relocated away from the ocean.
The ultimate experiment would be to mount the vertical out on the shelf at low-tide, allowing the ocean to pour in underneath it at high-tide.
Seawater Spills Over onto the Shelf
Enabling the installation of phased verticals at low tide subsequently swamped, along with their elevated radial fields, at high tide.
UPDATE: AUGUST 5:
A Finer Point of Elevated Phased Verticals Confirmed
Using toroids, ugly-baluns or voltage baluns as current chokes changes the phase relationship between the verticals, diminishing F/B performance.
Removing the toroids pictured above returned the F/B ratio exhibited prior to their installation.
Only ferrite beads slipped over the coax at the feedpoints can be used in elevated phased verticals. Other common mode current chokes, such as wrapping the coax around a torroid, voltage baluns and ugly baluns, change the phase relationship between the verticals. The screen provided by the 30 elevated-radials per vertical in our installation reduces common mode currents along the feedlines, which are allowed to drop down from the feedpoints and then run on the ground to the switching box without any chokes installed.
UPDATE: January 1, 2017
UHER M517 DYNAMIC MICROPHONE
Being used while SONY ECM-55B microphone is being repaired
Both condenser microphones crapped out due to electro-mechanical failures. While repairs are being affected, using an old UHER M517 dynamic microphone pulled from storage. Requires equalization to reduce lower frequencies. Repair of the condenser microphone requires micro-surgery, which is time-consuming. Hoping the audio from this old UHER reel-to-reel tape recorder microphone is acceptable.
UHER M517 Dymanic Microphone (circa 1972)
Used while SONY ECM-55B condenser microphone is being repaired.
UPDATE: DECEMBER 25, 2016
RESTORING NATIONAL HRO-500 RECEIVER
Removal of Front Panel & General Inspection in Preparation for Re-capping
A National HRO-500 receiver has been pulled from storage in order to be restored this January, after which it will serve as the station's main receiver and thus relegate the Kenwood TS0-520 to transmitting duty.
National HRO-500 Receiver
Initial inspection. The main tuning dial was cleaned with Brasso using a soft rag and toothbrush. The remaining knobs were put through the dishwasher.
Front Panel Removal
Removing the front panel eases access to the inner gear mechanisms, and the replacement of rusted pilot lamp sockets. It necessitates the removal of 8 stainless steel flathead screws securing the the top and bottom of the front panel to the chassis, as well as several self-tapping hex screws along the side gussets. All of the nuts holding the controls to the front panel must also be removed. In our case a Dremel tool had to be used to split a stubborn, warped toggle nut. After that, a screw holding the S-meter lamp socket must be removed, followed by a light aluminum nut holding a C-shaped aluminum plate fitted around the back of the S-meter. There is no need to remove any of the Phillips-head screws in the face of the front panel.
Removal of Front Panel
Eases access to mechanical assemblies and pilot lamps.
After the plexiglass windows were cleaned with warm, soapy water, the gears are inspected in preparation for cleaning and re-lubing. All fasteners are returned to their respective locations in order to keep them organized prior to reassembly. Peeking into one of the oscillator sections lifts spirits while exposing several of the electrolytic capacitors which will be replaced. The HRO-500 will now be set aside until arrival of replacement components in mid-January.
UPDATE: DECEMBER 21, 2016
THE PERFECT PILE UP • Europe & Asia
7135 Khz • Captured on YouTube
The video below demonstrates how the large F/B ratio exhibited by the phased verticals helps suppress American QRM when working eastward DX on a busy band.
The December 21st Euro-Sino Pile-up
Stations include: IZ8GCP DK2RZ/m G4AIR IT9NDW JO1DZA CN8WL HB9EYP IZ1WWX IU5HIB G4DOQ JH3FMJ FM5WE EA5DTX JH7MQD DK1RU IK5ORP I8VJK 4X6TT CM7OA
UPDATE: DECEMBER 20, 2016
DISASTER STRIKES • Beverage Destroyed
Windstorm from Hell Takes Out the West Beverage
Tree Lands on West Beverage
Dead tree explodes on a cold Winter night, taking out the Western Beverage.
Through the howling winds a loud crack is heard in the middle of a cold winter night. I rise from the kitchen table and walk over to the sliding glass door, peering through the 3-degree F chill outside. Premonitions of a tree taking out the elevated counterpoise systems are possibly confirmed by the sound of a second, more prolonged cracking. Trunks are finding their final resting place. Switching on the exterior light does nothing to illuminate the phased verticals out in the woods. The next morning, early--when attempting to work VKs--the West Beverage doen't appear to be exhibiting any directivity. After a hearty breakfast, a site survey is conducted. What is discovered? Watch the video below.
Survey Team Makes Its Way to the West Beverage
UPDATE: DECEMBER 5, 2016
SALTWATER VERTICAL QSOs • JAs Longpath • Mobile-to-Mobile UK-USA
VA2DF enables W1ZY/P to work JAs longpath with 50 watts • M0UOO/P peaking 59+40dB using phased saltwater verticals
Have been doing some portable vertical work along the coast, mostly at Point Judith, Rhode Island, working JAs longpath with the VA2AM DX Group (7128 Khz @ 4 PM EDT). This is because the main station's Kenwood TS-520 is on the bench for a few days to complete restoration work, including chasing down a problem with the ACG & S-meter, as well as to replace the jack to the CW key on the rear panel and get the VOX operating. Thus we are not operational at this time at the home QTH, and get in some radio time by using the IC-706MKIIG in the car, along with the 21' loaded portable vertical, which is working nicely. One upcoming project will be to relocate the loading coil higher up in the portable vertical in an attempt to increase its radiation efficiency. At the present moment, it takes abotu 10 minutes to assemble the portable vertical and about 5 minutes to break it down. Everything fits through the small boot of a 1999 VW Cabrio, if we pull the back seat down to allow for the single 6' aluminum tube section at the top of the portable vertical. Some great signals are being copied from Japan longpath, as well as some obscenely bodacious European signals shortly after sunset.
W1ZY/P Piggybacking off VA2DF, Working JAs Longpath with 50 Watts
Portable vertical mounted over Atlantic Ocean • Two elevated radials
Point Judith, Rhode Island • December 4, 2016
Mobile-to-Mobile Transatlantic QSO • M0UOO/P 59+40 dB
M0UOO/P in QSO with W1ZY/P
Phased Verticals in South Hampton, UK to Single Vertical at Point Judith, Rhode Island • December 5, 2016
UPDATE: NOVEMBER 1, 2016
Choking & Raising the Height of the Elevated Phased Verticals
W2DU baluns enhance system performance prior to raising the base-heights to 18 feet in preparation for Winter
It has been thus far assumed that 30 counterpoise wires per vertical sufficiently screens the two 84-degree feedlines from common-mode currents. This assumption has been proven wrong by enhanced F/B performance after installing W2DU "current baluns" at both feedpoints. The F/B response has deepened in the phone segment of the band, and has extended itself down to the CW portion. It is believed the common-mode currents apparently choked by these devices are exasperated by an 8-ohm reactive component yet to be eliminated at system resonance (7.1 Mhz). This residual reactance might be due to the counterpoise wires being too long for the targeted frequency--the thinking being that after we adjust the lengths of the verticals to achieve resonance at 7.1 Mhz (34'11"), we do so against counterpoise systems that are a wee bit too long (36'), resulting in each vertical-counterpoise combination being fed slightly "off-center". When each vertical is swept with the antenna analyzer, we find its reactive component dipping at the targeted frequency, but never reaching zero. As an aside, the physical symmetry between the verticals is replicated in their impedance and reactive sweeps.
Other possibilities include:
(i) The MFJ antenna analyzer is out of calibration.
(ii) The counterpoise wires are not equally-tensioned, thus presenting different electrical lengths at the target frequency (7.1 Mhz).
(iii) My use of 246/f to calculate vertical element and counterpoise lengths should be replaced with use of 234/f.
W2DU Baluns Installed in East & West Verticals • Increases Depth & Bandwidth of Front-to-Back Ratio
Pigtails pruned to bring feedlines to their requisite 84-degree lengths.
Assembled from kits purchased from The Wireman ($11 each).
It is summized that the reduction of the diameter of the counterpoise systems may eliminate the residual reactance presently seen at resonance. And that this diametral reduction might be obtained as a concomitant of the (separately-planned) raising of the system height from 12 feet to 18 feet--the thinking being that the downward slope of the elevated radials will reduce the counterpoise diameters sufficiently to eliminate the residual reactance presently found at resonance. The elimination of this reactance minimizes the voltage between the counterpoise centers and ground, thus reducing ground losses to the fullest practical extent.
UPDATE: It has been calculated that increasing the heights of the verticals will not suffice to reduce the diameters of the counterpoise systems as discussed. Therefore, the sixty (60) counterpoise wires are being individually trimmed from 36' to 34' 11". This will take several days and necessitate re-resonating the vertical elements.
UPDATE: With one-third of the East counterpoise system shortened, there is no change in the system's impedance and reactive curves.
UPDATE: Shortening the East counterpoise has altered the system impedance, reactance and SWR sweeps, as detailed below. The East vertical now resonates at 7.125 Mhz, while the West vertical remains at 7.080 Mhz--both with 10 ohms reactance--measured at their feedpoints with both disconnected from cables. The lengths of the verticals has not been changed.
System Impedance, Reactance & SWR Sweeps • November 17, 2016
As measured at remote relay after trimming East counterpoise system from 36' to 34' 11".
With radial (re)tuning the system impedance fluctuates between 36 and 50 ohms with a reactive component below 30 ohms. Although the SWR sweeps appear off-set by a constant value, their general alignment might reflect the efficacy of the Christman phasing method. The non-conformity of the reactance sweeps might be better understood upon review of phased verticals theory. To wit, quadrature-phased verticals create a condition wherein the vertical closest to the forward lobe radiates more energy in spite of the fact that the phasing scheme "forces" equal currents between the two vertical feedpoints. Mutual coupling establishes this unequal radiation, which is the basis of the array's directive pattern, leading to the "front" vertical "having more energy" than the "rear" vertical.
The East sweep represents system reactance when the East vertical has more energy in it, and the West sweep represents system reactance when the West vertical has more energy in it. This observation gives rise to the theory that the "dominant" vertical "dominates" the system reactance sweep. Assuming our trimming of the East counterpoise has caused its vertical to resonate "more deeply", when we set the directive state to the East--causing the East vertical to be the dominant radiator--the (blue) system reactance sweep is smoother and devoid of the excursions measured when the directive state is set to the West. Under such conditions, the variations in the (red) system reactance sweep might reflect the West vertical operating against a counterpoise system yet to be trimmed, while being coupled to the differently-tuned East vertical.
The differing reactance sweeps are produced when the 71-degree delay line is added to one or the other of the (84-degree) feedlines feeding the verticals. When we add it to the East vertical's feedline, the system reactance is nice and flat. When we add it to the West vertical's feedline, the system reactance goes beserk. This effect must have something to do with a difference between the two verticals--the most obvious of which presently being the disparity between the lengths of their counterpoise wires (34' 11" vs. 36'). Outside of that, there is no difference between the two verticals (other than, perhaps, widely-variant ground conductivity). The next stage of this experiment entails trimming the West counterpoise system to that of the East vertical (34' 11"). After that, we can measure the impedance, SWR and reactive sweeps again, and compare these readings to those provided above. Hopefully we will see the East & West sweeps align themselves--especially after re-resonating the vertical elements.
UPDATE: With the West Vertical counterpoise 50% trimmed, the following system measurements were recorded at the relay box. Note the alignment of the East/West curves.
System Impedance, Reactance & SWR Sweeps • December 2, 2016
As measured at remote relay after 50% trimming of the West counterpoise system from 36' to 34' 11".
And here's the two sweeps side-by-side. *** This situation is admittedly a mess, and looks like it will require lengthening the counterpoise wires in accordance with the 5% longer rule. Of interest is the fact that the F/B performance is not affected (so far) by the trimming of the counterpoise wires. All we know right now is that the curves for the two directive states are aligning themselves as we finish trimming the West counterpoise system. The problem is that the reactance and impedance values are heading in the wrong direction, both getting higher than when the system was using the longer, 36' counterpoise wires. So the shortening of the counterpoise wires appears to have detuned the system, as far as the impedance and reactance values are concerned. At the same time, this trimming has caused the curves of the directive states to align themselves. None of the readings provided above reflect re-tuning of the vertical element kengths, which has yet to be attempted. Recent readings indicate the East vertical is showing least reactance at 7.125 Mhz, which is a bit higher than its original resonance at 7.108 Mhz earlier this summer (with the 36' counterpoise wires. And the West vertical is showing resonance at 7.080 Mhz, which is 25 Khz lower than earlier this summer. ***
UPDATE: DECEMBER 2, 2016
Year's End Review
Pictoral of Elevated Counterpoise System After Being Prepared for Winter Season
Here are some photographs of the phased vertical system shot earlier this morning. We ended up applying three coats of Liquid Electrical Tape to weatherproof the grounding rings on both verticals, and then added W2AU ferrite beaded current baluns at the bases of both, which increased the F/B performance and extended it to the CW portion of the band. As part of preparing the verticals for the Winter, we also trimmed the counterpoise systems--shortening them from 36' to 34' 11", despite objection from Old Timers. This turns out to likely have been an error. We should have lengthened them in accordance with the 5% longer rule, which will be done after we complete trimming the West vertical counterpoise. The logic being to take a third set of system measurements for the sake of entering these values into the Project's scientific notebook, and then perform the experiment of inserting small coils between the shields and grounding rings of each vertical to see if this reduces the reactive component discussed above. Finally, as part of the work done on the counterpoise systems in preparation for Winter, they have been retensioned which realigns the insulated spacers at intersecting points to electrically isolate the counterpoise systems from one another.
UPDATE: JANUARY 22, 2017
Restoration of a 1946 Hallicrafters S-40A General Coverage Receiver
While the National HRO-500 awaits parts, we have begun the restoration of a 1946 Hallicrafters S-40A.
That's what they look like when fully restored. This one was done by Jeff Miller
Our journey begins with a not-too-bad specimen, acquired in 2005 off eBay for $30.
1946 Hallicrafter S40-A: Faceplate & Cabinet
After a thorough cleaning, the faceplate and cabinet emerge intact. No dents.
Chassis: Top and Bottom
Chassis cleaned up after a thorough cleaning with dishwater liquid, followed by Brasso and cotton rags.
Beneath the chassis lie the original components, including paper capacitors and blown power resistors.
Bandspread Flywheel & Transformer Case
The tuning capacitor and pulley mechanism are removed from the chassis and cleaned. While being spun by a cordless drill, the flywheel is slathred with Brasso and buffed with cotton rags.
The pully mechanism is reinstalled and lubed with Mobil 1 and white lithium grease. The top of the power transformer is then removed, sanded, primed and painted.
Restoration forums say the rust spots on the chassis can be removed through application of Naval Jelly with Q-tips.
No interest in doing that here, for this not a museum-grade restoration. It's a W1ZY clean-up.
Arrival of Components from Just Radios®
Elation greets the arrival of capacitors and power resistors
Enlarging the S40-A Schematic
After being downloaded from the internet, a high-resolution S40-A schematic is blown-up and printed on 8.5" x 11" sheets of photographic paper, which are then trimmed and taped together.
The resulting mosaic--measuring 3 feet by 2.5 feet--is then populated with useful information, such as resistor wattages, power busses and cathode return circuits.
Schematic Hung Over Workbench
With its hanging over the work bench, the schematic acts as a road map when tracing point-to-point wiring in the chassis.
Prior to that, a magnifying glass was needed to read a smaller schematic.
Re-capping with the Foil-Side of Capacitors Towards Ground
The rewarding work of re-capping the radio begins. Care is taken to connect the "foil-side" of capacitors to the part of the circuit closest to ground potential. This reduces hum.
To check a capacitor, hold it between your fingers while touching each lead with an oscilloscope probe. Your fingers act like an antenna. Whichever lead shows MOST hum on the scope is the "foil side".
Rebuilding the Power Supply
Although the can capacitor remains in the chassis, it is disconnected from the circuit. It is replaced by fresh electrolytic capacitors which are mounted along a terminal strip.
At first, high-wattage resistors are wired to the terminal strip to check voltages. But then they are then moved to the rear of the chassis, and stacked like rifles in the back window of a F-150 between two terminal strips.
This protects other components from the heat they generate, and eases their measurement and eventual replacement in the future.
Low-wattage resistors connected in series & shrink-wrapped allow the testing of voltages while waiting for the arrival of a high-wattage resistor.
The original tube rectifier (80) was initially supplanted by silicon diodes; its filaments were left wired for visual effect.
However, the rectifier tube was re-introduced after it was discovered that the higher efficiency of the silicon diodes registered a 10% increase in plate and screen voltages.
New "Fender" Toggles & Switchcraft 1/4" Headphone Jack
S40-A toggle switches are replaced with new "Fender" switches ($4/ea.).
The new toggle switches and headphone jack enhance the pleasure derived from operating the antiquated shortwave receiver.
These new items will spruce up the appearance of the restored radio since they are the only controls exposed on the front panel. All others being concealed by Hallicrafters "cupcake" knobs.
#44 Pilot Lamps Arrive
6-Volt pilot lamps are installed upon their arrival from Antique Electronic Supply (10 for $3).
The dry and cracked powering wires are ensconsed in shrink-wrap tubing. Done.
Tuning Pulleys Restrung
New dial cord is restrung upon its arrival from Antique Radio Supply (8' for $8).
This completes restoration of the tuning mechanism. Done.
Just a pretty picture taken by a proud father.
JANUARY 32, 2017
The Aesthetics of the Front Panel & Cabinet
After getting the final screen-dropping resistor in place, and checking the voltages throughout the circuit, we put the chassis aside to work on refinishing the front panel and cabinet. At the top of this list is obtaining a perfect color-match between the old and new paint. I thought this might be impossible since the Hallicrafters S40-A has a unique color, which does not appear to be black. It appears to be slightly lighter than black, with perhaps an olive or green or blue tint to it. But this does not turn out to be correct. What happens is that when flat black paint is applied, the metal does something that causes the color to match the original color--as we shall shortly see.
First I turned my attention to the front panel. I cleaned it with "Super Clean", available at Home Depot, WalMart and auto stores. This really cleans the chassis and cabinet of old radios.
After cleaning the front panel, I then made a number of measurements depicting the placement of various labels on the panel. A lot of photographs were taken during this stage, along with measurements and copious notes taken down on paper. This produces a record for the precise placement of decals after the panel has been painted.
I then sanded and cleaned the front panel with Spray Clean, and then rinsed it. And then cleaned it again with Acetone, after which I hit it with a tack cloth to get every, last anal-compulsive speck of anything off it. Nerviously, I began shaking a can of Rustoleum Gray Auto Primer. With the front panel leaning against the bottom of one of the re-cycle containers, previously used to restore the SB-221 last Spring, I rolled my office chair up to the victim. I lowered it and began to spray the panel--hoping I was not making a mistake. When I was through, I placed it kitty-cornered over the edge of the table and the operating position to let it dry over the electric (oil) heater which I rolled beneath it. The paint can says it takes about 10 minutes to dry. I am nervious. All the patina coveted by The Collectors is gone. Jitterly, I go into the kitchen to get some coffee. When I return, I almost drop the cup when I see what I had done...
Dayem! It looks great! I might not even paint the black on it. I take a swig of coffee admiring the thing, and set the cup down. Determined to experiment, I flip the front panel and paint the backside with the the Kyron flat black--just to see what it looks like. Just to see if it is too black. I put the panel back kitty-cornered over the edge of the operating position and up-loaded some of these photos to the QRZ.com page. As you know, that took several hours. Just kidding. A few minutes later, I check out the panel. Dayem again! It looks even better than the gray primer! I shake the can of flat black Krylon, which I had left on the radiator to warm up, and start spraying the front panel. As McDonald's says, "I'm Luvin' It!" After three coats, the front panel pretty closely color-matched the original paint--as seen in the photograph below.
Very nice match. So we are now prepping the cabinet for the same treatment. Start with the perforated top. Remember to spray the paint in at angles at the end in order to get the sides of the perforations, where rust is often times lurks.
The perforated top comes out perfect. Three coats. I then sand and clean the cabinet, getting it ready for the primer.
After the auto gray primer and two coats of the Krylon flat black, this is what we get. Yes.
Now we perform a partial re-assembly sans chassis.
The types of paint I used were Rustoleum Automobile Primer (gray), followed by Krylon "Colormaster" Flat Black. That's what you see applied iin these photographs. After putting the decals on, I used Krylon Clear Coat (gloss). This brought the color down to true black, which was a slight disappointment because I liked the hue of the flat black. It matched the original Hallicrafters finish perfectly. So if I did it again, I might try using Krylon Clear Coat (matte), if it exists. Perhaps that would not cause the same darkening of the base coat color. You will see what I am talking about a bit further down in the photographs depicting the front panel after application of the decals. Until then, check out the nice results from using the flat black.
We are now ready to put the decals on the front panel. Stay tuned....
Application of the Decals
The decals were ordered from Antique Electronics Supply ($15). Although the restoration forums all reported that one needed to use a watercolor paintbrush to position the decals after they had been slipped off their paper backings, I found use of my index finger more convenient. As seen in the photographs below, the decals worked wonderfully. At first you could see the trim off to the sides of the decal lettering. But this totally disappeared after application of clear coat to seal and protect the decals. As previously indicated, application of the clear coat also darkened the hue to the base coat, bringing it to true black. No worries, though. The results were quite acceptable--expecially when compared to the original condition of the receiver cabinet.
Before & After
Comparison between the original S40-A front panel and after application of decals and one coat of clear coat.
A General Overview
One coat of clear coat is seen depicted in these photographs of the front panel, which appears to provide sufficient protection to the decals without raising the gloss of the front panel's finish.
In this restoration, however, several additional layers of clear coat were applied to raise the gloss of the front panel, as seen in subsequent photographs.
Do not be afraid to cut the decals as close as possible to eliminate trim area. Once they are coaxed from their paper backing, they can be positioned with a watercolor brush or an index finger with ease.
After getting the decal positioned properly, a dab with a Kleenex removes excess water. Pressing down on the Kleenex also secures the decal to the front panel surface.
Detail of Decals
When first applied, the film of the decals is clearly visible. However, it disappears after application of one coat of clear coat.
A slight is evident in the "the" of the Hallicrafter decal, which was subsequently touched-up with a watercolor brush dabbed with a smidgen of flat black paint. Additional layers of clear coat followed.
On the right, a small defect can be seen int he paint, which was sanded down and re-painted before adding more layers of clear coat.
Clear Coat: Before & After
For anyone about to do this restore, the photograph on the left shows the luster of the front panel after one coat of clear coat. On the right we see the luster after 7 additional coats.
Details of Decals: S40-A & The Hallicrafters Co.
Seen above are the finished states for the S40-A and Hallicrafters decals.
We can see the removal of the blemish from the panel finish previously seen below the S40-A decal, as well as the removal of the film artifact from the "the" of the Hallicrafters decal.
High-gloss Detail of Front Panel
Above we see the result of 8 layers of clear coat (gloss) applied over the flat black base coat.
Preparation of the Dial Plate
Blue painters tape protects the dial plate glass from paint. The plate assembly has been sanded with 600-grit sandpaper.
White-Out has been rubbed into the band position numbers in an effort to reclaim them after painting.
The idea being to pick the White-Out out of the numbers and re-apply White-Out.
Dial Plate: Before & After
Here we see the dial plate after priming, painting and clear coating.
Initial photography of restored S40-A.
The receiver will be set aside in the warm house for several days to allow the clear coat to harden.
Coming Up Next
Aligning the receiver with a sweep generator...
Here's a little movie of the S40-A depicting its operation (without smoke) prior to alignment.
UPDATE: March 13, 2017
CONVERTING THE WEST BEVERAGE INTO A 2-WIRE REVERSIBLE AFFAIR
With Spring around the corner, now's the time to enhance reception to the East
How a Beverage Works
What follows is a simplistic explanation of how Beverages work which will make physicists cringe--beginning with a neat animated gif I found on the WikiPedia listing for Beverage antennas.
The Single-wire Beverage
Forward-direction Signal Builds-up Along the Wire
When a signal arrives from the front of the Beverage antenna, it builds up energy as it travels down the wire. When it reaches the end, it passes to ground through a broadband transformer that couples it to the receiver through a length of coaxial cable. The primary and secondary windings of the transformer are respectively matched to the characteristic impedances of the wire (450 Ohms) and coaxial cable (70 Ohms). This maximizes the transfer of the signal from the antenna to the receiver.
Signal From the Opposite Direction Goes to Ground Through a Resistor
A signal arriving from the opposite direction--e.g. behind the Beverage--also builds up energy as it travels down the wire. When it arrives at the end, it passes to ground through a resistor connected to a ground rod. This gets rid of the signal so that it does not reflect off the end of the wire and show up in the feedpoint transformer at the other end. The value of the (terminating) resistor is equal to the characteristic impedance of the wire. This maximizes the draining of the unwanted signal off the wire to ground. This is how a Beverage is configured to receive signals from only one direction. If the resistor is left out, the Beverage will receive in two directions--e.g. off both ends.
Terminating Resistor at the Far End of a Beverage
The terminating resistor is matched to the characteristic impedance of the wire to provide unwanted signals a "perfect match" to ground. The "1:1 SWR" to ground also minimizes the reflection of the unwanted signal back to the feedpoint transformer at the other end of the wire.
Down the Rabbit Hole
The antenna enhances signals that travel down it, and rejects signals that arrive perpendicular to it. Thus, radio waves arriving perpendicular to the wire instantaneously induce energy along its entire length. This occurs over the amount of time it takes the radio wave to travel through the diameter of the wire. These perpendicular waves do not build up along the wire as do waves that arrive off either end, which incrementally induce their energy into the wire during the time it takes them to encounter the wire. To get an idea of how much longer end waves (e.g. "end wavefronts") interact with the wire compared to perpendicular waves, we can divide the length of the wire by its diameter. The resulting huge number tells us how much longer end wavefronts interact with the wire compared to perpendicular wavefronts. It also shows us that the longer the Beverage, the longer the time end waves get to deposit their energy into it. And that the time alotted perpendicular waves remains the same, for the only way to increase this amount of time is by increasing the diameter of the wire. This phenomenon partially sculpts the side-rejection exhibited by Beverage antennas. There is another interesting phenomenon, however. And it has to do with the fact that the antenna wire conducts electricity from one end of the wire to the other end.
Antenna Wire Conducts Induced Currents
As the end wavefront encounters the wire at the speed of light, at some point in time it will be halfway down the wire. At this point all of the energy induced into the wire by the end wave is being conducted by the wire, itself, and--in accordance with its velocity factor--is traveling slightly behind the end wavefront as both approach the feedpoint transformer at the other end. This is what we mean when we say that waves arriving off the ends of the Beverage "build up energy" as they travel down the wire. And this means that even the feeblest of currents induced into, say, the first 5 or 10 feet of the Beverage will make their way to the other end, and will therefore be included amongst the cumulative energy delivered to the feedpoint transformer.
Energy Arrives On-time
Since the wire conducts the cumulative energy at slightly less than the speed of light, the energy induced in the first 5 or 10 feet of its far end will arrive at the feedpoint transformer at almost the same time as the energy induced in the last 5 or ten feet of the wire. Let's calculate this delay while physicists shake their heads in disagreement.
Question: How much far behind a 7 Mhz wavefront is the cumulative signal (conducted by the antenna wire) by the time it hits the feedpoint transformer in a 100 meter long Beverage?
Answer: About .01 microsecond.
Time it takes the wavefront to travel 100 meters in free-space: .00000034 seconds
Time it takes the cumulative signal to travel 100 meters of wire (.95 velocity-factor): .00000035 seconds
Difference in time: .00000001 second, or .01 microsecond
Phase shift @ 7 Mhz: 25 degrees
The take away is that perpendicular wavefronts do bear any of these consequences because they encounter the entire length of the wire at the same instant. The current they induce into the traveling wave antenna is instantaneously disbursed throughout its entire length. When they cycle from positive to zero to negative and back to zero, the current they induce follows this progression throughout the entire length of the wire. There is no opportunity to "build-up" as the wavefront progresses down the wire, with the cumulative current following close behind the wavefront.
If you've followed this explanation so far, you're really close to understanding how Beverage antennas work. There's a couple things we've left out. One has to do with a quality of the radio waves exciting the Beverage antenna, which is related to the second thing; namely, why the Beverage antenna needs to be close to the ground to to receive long-distance signals. When we mix these two remaining concepts into our understanding of how the Beverage works, physicists will cringe a little bit less, and we will have arrived at a decent understanding without using any math.
Why Does a Dipole Work the Opposite Way?
Before we mix-in these missing ingredients, let's first take a moment to acknowledge and address the elephant brought in the room by our explanation; namely, Why is it that a dipole works the exact opposite way? Afterall, signals arriving perpendicular to it are enhanced, while signals arriving off either end are diminished. How can a Beverage work the opposite way? The answer lies is in the fact that a dipole (or vertical monopole) are resonant antennas, which means the currents induced in them flow in both directions as a result of bouncing (reflecting) back and forth between their ends. This creates what we perceive as standing waves of energy which we interpret as current and voltage maximums and minimums disdtributed along the lengths of resonant radiators. Thus a half-wave dipole, for example, exhibits a current maximum at its center and current minimums at its ends. And voltage maximums at its ends with a voltage minimum at its center. These perceptions, in turn, are translated by engineers into varying "feedpoint impedances" along the length of the resonant radiator which, in turn, allow for different excitation schemes: e.g. 50 Ohm coax at the center; a balun when fed off-center, etc.
The Beverage is a Non-resonant, Traveling Wave Antenna
The Beverage antenna is not a resonant antenna. It is classified as a "Traveling Wave" antenna which operates, essentially, along lines provided in the explanation we have thus far mastered. With the proviso, again, that we need to add in a couple more items before we can arrive at an understanding without using any math. The two things we need to add address the questions of (i) Why does the Beverage have to be so close to the ground in order to (ii) enhance reception of long-distance (DX) signals? Both have to do with a physical property of the radio waves that excite Beverages, as explained below.
Meat & Potatoes
Because it is a low-noise DX receiving antenna, Beverage aerials have a preference for low-angle radio waves that arrive almost parallel to the ground after having been bounced off the ionisphere far, far away. These types of DX signals are the Beverage's meat & potatoes.
Bending Forward When Kissing the Ground
And there is a quality ascribed to these low-angle DX signals upon arriving at the end of their journey a few feet above the ground. They do not possess this quality if you intercept them high up in the air with a dipole or a yagi. You can only perceive this quality by intercepting them a few feet above the earth. For it turns out that these low-angle DX signals are subjected to a "ground-effect" that slows them, causing their vertically-polarized electric field to tilt forward. This gives rise to the generation of smaller electric fields that happen to be parallel to the ground. This is a unique situation. For if you string up a long wire a few feet above the ground, it will be excited by these small electric fields that are parallel to earth. So when we talked earlier about radio wavefronts interacting with the Beverage antenna wire, it was these weird electric fields parallel to the ground to which we referred.
A Freak of Nature
The ground effect that slows down the DX signal, causing its electric field to tilt forward and spew-out the smaller electric fields parallel to earth, is a freak of nature that gives rise to such oddities as a long, low wire being a good long-distance receive antenna. And that this long, low receiving antenna is vertically-polarized! Strange, but true. Beverages are vertically-polarized. This is because the small electric fields that excite them--even though they are parallel to ground--are part of the vertical (electrical) component of the incoming radio wave.
Back Down the Rabbit Hole
Because the incoming radio wave is slowed down when it gets close to the ground, the small electric fields it produces are also not traveling at the speed of light. And neither are the currents they induce into the long, low antenna wire. The currents in the antenna wire, in turn, are slowed down even further by the same "ground-effect" that slowed the incoming radio wave. In this case, the proximity of the antenna wire to ground slows down the flow of current thorugh it the same way the dielectric in a coaxial cable slows the propagation of a signal through it. Because the height of the antenna wire is fixed, the degree to which the "ground effect" slows down the flow of current in the wire is fixed. But this is not true in the case of the incoming signal; the degree to which it is slowed by the ground-effect depends on its angle of arrival. When the speed of the incoming signal equals the speed of current flowing down the antenna wire, the cumulative signal delivered to the feedpoint transformer is maximized. This sculpts the forward-lobe of the Beverage antenna.
The Angular Sweet Zone
This is an interesting point, because at the beginning of this explanation it was posited that the traveling wavefront and culmulative energy arrive at the feedpoint transformer almost at the same time. We even calculated the delay as .01 microsecond (for a 7 Mhz signal along a 100 meter Beverage). This inaccurate representation was admitted into the initial explanation in the hope that it would help you get to this more advanced understanding. The more accurate explanation is that the arrival angle of the incoming radio wave causes it and the current it induces into the antenna wire to arrive at the feedpoint transformer at the same time. And that when they do, maximum Beverage performance occurs. The take-away is that angle at which the incoming signal encounters the Beverage creates a "sweet zone" vis a vis the aerial's performance.
ANGLE = ARCOS (1 - WL/2L)
WL = wavelength of frequency being received
L = length of wire
MORE TO FOLLOW IN THIS CRAZY SECTION
Practical Notes of Interest
The Beverage offers two advantages: directivity and low-noise reception. Its directivity is derived from its length, while its low-noise receive capability is related to its low height above ground. This means that even if you don't have enough room to put up a full-size Beverage, you can put up a shorter one to take advantage of the antenna's low-noise reception--albeit from all directions. Or you can put up a full-sized Beverage, but not terminate one end with the resistor. Each configuration has practical applications. For example, if you are net control for a worked-all-states nets operating from the middle of the United States, a short Beverage provides lower-noise reception in all directions, while an unterminated East/West Beverage simultaneously extends low-noise reception to both coasts. In the video below, we hear the low-noise reception afforded by a short, terminated Beverage oriented NE/SW.
Listening to a Spanish Station on a Short (70') 40 Meter Terminated Beverage
AN400T in Spain • 7140 Khz • October 1, 2016 • 0200 UTC • Kenwood TS-520
Signals coming from the front build up in strength as they travel down the wire. When they reach the end, they are coupled to the receiver through the feedpoint transformer. Signals coming from the oppostie direction also build up strength as they travel down the wire. But when they get to the end, they are provided a "perfect match" to ground. The "1:1 SWR" offered by this "perfect match" minimizes the refelction of these signals off the end of the antenna back to the feedpoint, where they would show up in the receiver. If we want low-noise reception in both directions, we do not terminate the far end of the Beverage. Even if we don't have enough room for a full-size Beverage, we can still get lower-noise reception by stringing up a shorter version.
The Beverage needs good RF grounds at both ends to work. Ground rods are not enough. But they are a starting point. They can be fashioned from 5' or longer copper pipes, rather than copper-clad steel ground rods, which have a tendency of flaking over time. After driving the copper pipes into the endpoi9nts of the Beverage, you should run out several radials along the ground attached to these pipes. Avoid running any radials that line-up with the Beverage wire, though. 1/8 wavelength is a good length, but anything shorter than that is better than nothing at all. I use old wire coat hangers bent into U shapes to staple the ground radials to the earth. These rod/radial systems stabilize the ground systems at RF frequencies at either end of the antenna. This simplifies the tuning stage by removing poor grounding as a possible reason for poor performance.
Winding the $1 Amidon BN-73-202 Feedpoint Transformer
The 450 - 75 Ohm feedpoint transformer is wound on a small, Mix 73 binocular core (Amidon BN-73-202). Mouser sells the cores for about fifty-cents apiece.
You can use #26 enamel wire, or #22 insulated hook-up wire. If you use the former, a couple pieces of spaghetti inserted into the holes of the binocular core protects the enamel wire from the conductive, ferrite core. Insulated, stranded hook-up wire serves the same purpose.
70-ohm coaxial cable: 4-turns for the primary winding (antenna-side), and 2-turns for the secondary winding (coax-side).
50-Ohm coaxial cable: the primary is 5-turns, and the secondary is 2-turns.
Keep Track of the Windings
It's essential to wind the primary and secondary in the same direction through the binocular core. And to keep track of which lead constitutes the "beginning" of the winding and which lead is the "end" of the winding. It can get really complicated, so it is best to stick short pieces of masking tape on the leads and label them (18.104.22.168. etc) as you wind the transformer. That way you can be assured that the "beginning" leads on the primary and secondary are attached to the "hot" signal, and the bottom leads are connected to ground. Or in the more complicated 2-wire, reversible Beverage--which has yet to be convered--to get correct the interconnection of multiple transformers. Otherwise, the thing won't work properly and you might end up adjusting aspects of thte aerial, such as its height, to no effect.
What Constitutes 1-Turn Around a Binocular Core?
"1-turn" means the wire passes through one hole, makes a U-turn and passes back through the other hole. "1/2-turn" means the wire just passes through one hole, ending up on the other side of the core. Such "1/2-turns" should be avoided because they create imbalance in binocular core transformations. In such cases find a greater number of windings that satisfies the turns-ratio while eliminating the "1/2-turn". The primary winding should be wound first, with care taken to wind the secondary over the primary windings. Do not tighten the windings too tightly around the core if using enamel magnet wire. Soldering the completed transformer(s) onto a circuit board makes them more durable.
Packaging the DevicesWhy Doesn't a Dipole Work the Opposite Way?
There are many ways to weatherproof the feedpoint transformer and terminating resistor. I use two methods. Initially, I place them into plastic electrical utility boxes available at GHome Depot for about $6. They are perfect, affording a lot of room inside to adjust things, removable lids with rubber O-rings and tabs along the base which ease their mounting on wooden stakes and/or trees.
Feedpoint & Termination Circuits Housed in Weatherproof Boxes
After tuning the antenna, I remove the utility boxes and use PVC tubes with end-caps to encapsulate the feedpoint transformer and terminating resistor. This provides an excellent means of long-term weatherproofing, and simplifies the means of mounting the devices to the grounding tubes in the field. They are also inexpensive to produce, and lend themselves to quick and easy replacement. Some ideas about how to do this are provided below.
Permanent Enclosures Fashioned from PVC Materials
The feedpoint transformer (left) and terminating resistor (right) are fitted within weatherproof PVC tubes.
Metal clips used to hang electrical conduit find perfect application when copper pipes are used for grounding rods
- More to follow -
7989034 Last modified: 2017-03-25 06:05:00, 488440 bytes
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