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QTH is near Canton Georgia, about 40 miles north of Atlanta.   

Primary:  Elecraft K3, P3, KAT500, KPA500, Heathkit SB-220 (built by WA4WDU), Behringer C-1 Microphone

Portable KX3,PX3,KXPA100

Secondary: Icom IC-725 (my first rig purchased from my Elmer, Paul, KJ4IS now AE4KR), Icom AT-500 tuner, IC-706mkII, AH-2 mobile tuner.

Antennas: 80m full size OCF dipole (similar to a Carolina Windom) in a "Y"  at 50ft , Cushcraft R7 vertical @ 30ft, Diamond V-2000 vertical @ 30ft.

Two reversable BOGs for N-S-E-W reception.

The OCF Windom sports a high power 4:1 torrid balun from Balun Designs.   Model-4125-4-1 Balun   This model is designed as a replacement for OCF Windom's that use a 22 foot vertical coax radiator section.  It's a voltage balun, so it allows RF current to flow down the feed line shield (on purpose!)   Thus, a feed line choke is required at the bottom of the vertical radiator section or else you will have RF running rampant in the shack!  The bottom of the vertical radiator section is choked off with a current balun formed by 5 coax passes thru five stacked #31 mix, 2.4 inch ferrite donut cores.  CM Choke Here is a photo of how it looks.

Current project:

Create a Virtual Machine image that allows you to easily update your MD-380 firmware and contact list using the MD-380tools project on github.  See

https://github.com/KD4Z/md380tools-vm

Last project:   Build a receive antenna system.  Specifically a reversible BOG (Beverage On the Ground) using RG-6 coax.   Being strongly influenced by Paul Casper's K4HKX  comprehensive page here on QRZ,  http://www.qrz.com/db/K4HKX , I decided a BOG project was in order.   I've twisted Paul's design a bit so that the feed-point of the BOG can be placed anywhere along the snake itself.  I plan to place it exactly in the center to allow for equal losses between the reversible directions.  It appears Paul likes my idea, and is now reconfiguring his BOGs to be center fed as well.

Typically, reversible BOGs are fed from one end, with a single Reflection Transformer at the other end.  This BOG setup will have two Reflection Transformer modules, one at each end of the receiving cable.  The Feedpoint Module then can be placed anywhere along the RG-6 receiving line.  My intent is to locate the feedpoint box exactly in the center. Relays are used to select which direction of reception is enabled and allows the antenna to be disconnected from the feed system when not in use.

The system includes two reversible BOGs oriented orthogonally in the compass directions of NE/SW and NW/SE.  A selection module will allow switching between the two BOGs allowing for 4 point primary directivity.  As it turns out, I implemented one of  the Bogs using the center feed layout, the other uses the more common end fed design due to site conditions.    Here are the BOG system diagrams I've cooked up.  This first graphic depicts the overally setup.

(Click image to enlarge in new tab)

Each BOG is reverseable using a dual relays.  The control signal is provided by a DC bias injected on the RG-6 feedline.   The stretch module allows the BOG to be electrically lengthened to allow for better multiband operation.   The base length of the BOG will be around 128 feet, optimum for 40 meters.  When stretched, the BOG will extend to approximately 200 feet to better support operation on 80m-160m.    The stretch module can be omitted to simplify the system.  This is the Center fed feedpoint module.

(Click image to enlarge in new tab)

This is the end fed version of the feedpoint module.  I ended up using this setup for the NW/SW Bog due to the way my site slopes downward.  This made the physical positions such that the two BOGs look a bit like a "T" .  This actually is the more commonly used layout for BOGs and reversible Beverages.

(Click image to enlarge in new tab)

The reflection transformer module is in the typical layout, however the stretch module adds an actively switched relay to provide for lengthening the BOG on demand.  When the control signal is enabled from the selection module, the stretch module relay engages and the reflection transformer becomes bypassed, and thus the snake is extended to the reflection module at the end of the RG-6 cable.

(Click image to enlarge in new tab)

Control is provided by a wireless link on 2.4 GHz using two Arduino Nano microcontrollers.   One Arduino is used in the station control panel, and the other is remoted by CAT 5 to the Bog Selection Module.  Commands are received wirelessly and are used to select which BOG is enabled, reversing state, and stretch state.  This also provides a nice lightning surge isolation factor.

 

The completed Control Panel.  The yellow pushbutton switches allow direct selection of the four ordinal points, and the green pushbutton toggles the stretch mode or auxillary 3rd antenna input.  Note the only connection is for 5V power.  The 2.4 GHz transceiver provides a wireless link to the Selection Module ( antenna is visible in this shot).

Here is the completed Center Fed Feedpoint Module which includes a Bias-T circuit for reversal.  The snake's shield passes through this box via the black insulated wire. The  transformers pick off the received signal from the center conductors from each leg, as selected by the relays, then passed through an aggressive Common Mode chokes made from 4  turns of  RG-179 coax passed through #31 ferrite cores.   A CM kit designed by the Yankee Clipper Contest Club, is obtainable from DX Engineering as part # DXE-YCCC-CHOKE.   However, you can roll your own using #31 Round Cable Cores (Fair-Rite 2631102002) for about $1.80 each from Mouser.com 

After measuring the common mode impedance of this kit, I decided to wind them as two separate chokes in series, instead of the intended design wound binocular style.  This improves the common mode impedance by 1000 ohms up through 40 meters by sacrificing some of the 8000 ohm impedance on 160m.  The kit obviously was designed for maximum effect on 160m only if completed per the original directions.    You can see the original layout of the choke in the center fed feedpoint module below.  The photo of the end fed feedpoint module shows the new layout of the CM chokes.

The output signal is available at F Connector at the bottom of the box.    When a DC bias voltage (approximately 12V) is detected on the output port, the relays activate, thus reversing which snake port is sensed and placing termination resistors on the other port.

This is the end fed version of the feedpoint module.

 

Here is the Bog Selection module.   Extra effort was required to stablize the power rails when the relays engage.  A LM7805 5 volt regulator is visible on the Bias-T board.  On a separate board, (tiny 1 inch square board in the picture) a 3.3 volt regulator was required as the 2.4 GHz transceiver requires more current on transmit (in high power mode) than the 3.3 volt regulator on the Arduino Nano could supply.

This is not a current photo however, as I have since moved the Nano board and the 2.4 GHz receiver out to a separate box using CAT5 and RJ45 connections.  This helps tame a few birdies in the 40m band, created by the Nano's clock.  Email me if you are interested in building the RF control link using the Arduino boards.  Although the RF link works fairly well, I'm still tinkering with the Arduino sketches, so I haven't posted them yet. You can of course just use manual switches to fire the relays as desired.

 

Here is one of three Reflection Transformers.  Each end of the snakes have one, and they are identical.   The purpose of the module is to reflect the received signal traveling along the outer shield of the coax, back into the center conductor, to be later picked off by the centrally located feed-point module.   Note the liberal use of Gas Discharge Tube (GDT) devices throughout all of these modules.  

Reflection Transformer

The transformers are made using binocular cores and #26 ga enameled wire.  The proper cores to use are type 73 ferrite material,  BN73-202 type.  ($.50 to $.90 depending where you get them)  The next picture is a closeup of a 4T/2T transformer made using these cores.  That's four turns on the primary, and two turns for secondary.   The surge impedance of the RG-6 shield, while laying on the ground, is approximately 300-400 ohms.  The 4T/2T transformer creates a 4:1 impedence transformation to approximately 75 ohms as the signal is reflected to the center conductor.    

 

There are many opinions floating around the Net regarding BOG performance versus length.   Paul K4HKX provided the following EZNEC / AutoEZ simulations of BOG front-to-back, front-to-rear, and RDF performance based on  the anticipated height of 0.1 ft (1.2 inches), over average earth (0.005/13). This represents my topography here at my QTH.   Paul automatically scaled the quarter wave ground radials in the simulation with frequency using the formula (29.38*(F/7.15)), which is based on some data from Jack, K1VT for the Velocity Factor of radials very close to earth.

Looking initially at front-to-back, it is easy to see why 128 feet is favorable on 40/30 meters, with decent coverage of 80m.  However it appears that even 200 feet might be a bit short for coverage of 160m.  Another model done by K4HKX suggests that a length of 280-300 feet would be optimum for 160m.  Since this length would compromise both 80m and 40m, I will use the stretch module to allow electronic selection of snake length.  RDF is considered more important than F/B as RDF considers the rear signals as a whole, not just from a single point to the reverse.  This is important as you rarely have the situation where the station you are trying to ignore is directly in line with your BOG.   If the BOG does succeed in obtaining an RDF over 11, that is quite good considering how easy they are to make, and how well they fit in small site dimensions. 

 

Project Status:

March 10, 2016 : Both the NE/SW and NW/SE Bogs are fully deployed and are both reversable.   Currently the NW/SE Bog is fixed at 128 feet until I can complete the stretch modules.  It is configured using the end fed design.   The NE/SW Bog is also fixed at approximately 164 feet using random scraps of RG-6.   More RG-6 has arrived but not deployed as of yet.

Initial performance:  This short video shows the difference between the NE Bog and the 80m OCF dipole while receiving a station about 800 miles away.   I apologize for the hand-held shake!  You should be able to tell the difference as I change the antenna selections.   Listen for the difference in signal-to-noise ratio.  The dramatic difference in the noise floor is partially due to the lower output level produced by the Bog.  In this video, I only had the built-in 20 dB preamp enabled on the K3 for the Bog.  For the OCF, the preamp was switched off.  You can add another preamp if you prefer the signals to be similar when switching between the Bog and other antennas.   I have the DXE preamp inline and enable it with power any time desired.  It self bypasses with out DC power.

click here for video

 

Prior Art:

I also own a wide area coverage 70 cm repeater located in Orlando, Florida.   KD4Z/R 442.250 + 103.5 CTCSS.  Feel free to use it if you are visiting the Orlando area.   Makes a good meeting place when attending Orlando Hamcation.

Originally KJ4IS/R, the repeater was a low power, solar powered system.  Now it is "QRO" at 26w, is at about 400 ft agl, and has a hot GaAsFet preamp (ARR) on the receiver so expect a 20 mile handheld radius.  It is flat Florida after all.   I routinely worked it from Port Canaveral, 50 miles away with a 30w mobile.

Here are some old shots at the KD4Z 70cm repeater site.  The 70cm repeater is a GE Mastr II mobile converted for full duplex.  The controller is a highly modified Scom 7K, (the 5K in the shot was changed to a 7K) with a custom CI-V controller I cooked up using a Basic Stamp microcontroller.  It made an Icom 725 into a remote HF base onsite at the repeater.    The system also supported Mic-E APRS packets dropped on the 70cm repeater input, which would be crossbanded over to the co-located APRS digipeater made from a surplus Motorola Mitrek. 

 

When I relocated to the Atlanta area in 2001, I removed the HF remote radio.  However not long after, I was able to reuse the Linux box that was co-located in the repeater cabinet as the first IRLP node in the state of Florida.  That lasted a few years until I lost the wireless internet connection due to the ISP going upside-down after too many hurricane claims for destroyed equipment.

The repeater has been on Echolink for a while after that, using an off-site uplink.  Now that we are tired of rebooting the Windoze machine so much, it's back to Linux and soon, we will have the repeater back on the Net as an Allstar node.  (Likely Echolink again as well)

Toys and diversions

I have long since moved on to Microchip PIC processors and have created some interesting things over the years.   Here is a totally home brewed GPS driven digital master clock using a single PIC PIC16F88‑I/P as a processor. It derives the time signature from a GPS module, and directly displays the time/date on a pair of I2c bus LED displays.  It also feeds data to a 902 Mhz transmitter, which dutifully transmits out a 1200 baud packet burst every 60 seconds.  That signal can be decoded by slave clocks to be automatically time/date synchronized over a block away from the QTH.  Had I thought to use a 5 volt compatible GPS module, I wouldn't have had to go through so much trouble level shifting between 3.3v and 5.0v.  (Note to self)  No external time setting switches are needed.  The time pops on the display after within 3 seconds from power up.  Local time is automatically adjusted for daylight time shifts.  (The decimal point to the left of the "9" in the time display is illuminated to indicate DST)  The GPS module has 16 parallel receiver channels and can get a decent fix inside commercial buildings.   The display alternates between time (8 seconds) and date (2 seconds)  All of the parts for this project were sourced from www.sparkfun.com   The microcode for the PIC is my creation, written in PicBasic Pro.  Send me an note if you are interested in recreating this clock.

 

 

Recently, I gave a presentation to the North Fulton Amateur Radio League (www.nfarl.org) on ham radio uses of the Arduino.   Here is a link to that presentation: 

Unique Uses for Small Computers in Ham Radio-Meet Mr. Arduino

As a result of displaying the GPS clock shown above during the presentation, many people expressed an interest in building one using an Arduino.  Here is a design I whipped up for a very simple GPS clock that displays date and time in UTC.  You can source the Arduino, GPS module and LED display from China for about $30 total!  Amazon has a u-blox NEO-7N with external antenna that works very well..about $20.  I just found the display on newegg.com for $2.   You can power the UNO with a 9 to 12V wall wart.

The source code for the Arduino sketch is here: GPSclockLEDverybasic.ino

Another useful project, here is a PIC based 4 channel power sequencer that I made to automatically control the power up timing of a DSL router, firewall router and microwave link radio.   It's in a remote site that has periodic power drops.  The issue was the firewall router would attempt to get an IP address long before the DSL router was ready to give it one.  The channels come up with a 60 second delay between each channel, starting when the power is reapplied.  This magical device saves a lot of trips to the remote site.

Fun with Linux

I have also had fun throwing a Raspberry Pi into the mix.  Although not ham radio related, here is a music streamer that I built for listening to my audio collection while at the office.  It emulates real Squeezebox hardware using an open source project called squeezeslave.   It connects to a remote Logitech Media Server (at my QTH) and directly drives a 2x40 LCD display.   A custom modification that I submitted to the project allows this device to act as a remote display for another squeezebox in the house.

Where did this all start?   Well, I first was introduced to Ham Radio back in high school but didn't take the test until much later.   At the time, 11 meter CB was popular, so I built a 3 element Cubical Quad for 11 meters out of PVC pipe and copper wire.  Plans for this great performing antenna was extrapolated from the 1974 ARRL Radio Amateurs Handbook.  It worked very well coax fed from the bottom vertex giving horizontal polarization. 

Ed Kranek holding my Cubical Quad for 11 meters

"The Five Amigos" 

8276659 Last modified: 2017-08-16 19:55:42, 22689 bytes

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