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Short Takes #8: Great Vertical Portable Antenna and KØNR's Book on VHF and Summits

By Dave Jensen, W7DGJ

The TNØ7 Portable Flagpole Antenna -- Many Possible Uses

I've followed the progress of TNØ7 Engineering for the last few years, primarily because I used to live in an HOA where I had to be very careful about my selection of antennas. Even though I have since moved to a big lot in a rural location (with no HOA interference), I check out Bob and Laura's new products now and again because they have antennas that fit nicely into special situations. While any "all bander" antenna comes with its own compromises, these TNØ7 models are interesting designs and especially well built.

I've seen a lot of their "green masts" sprouting up in RV parks around Arizona, so I wondered just how that Flagpole of TNØ7's would work on a POTA activation. I've now had a good chance to check that antenna out personally (model SFP-102) and have also interviewed a well-known POTA activator for his impressions. TNØ7 is a ten-year old, woman-owned small business, and I found them to be very cooperative and especially helpful as we began assembly. I have tried the antenna with a TNØ7 drive-on mount, with their trailer hitch, and have installed it into my own ground plate with radials in what I'd call a semi-permanent installation.

Here is a bit of detail from the assembly and initial inspection that I gave the antenna along with my ham buddy, Steve Bennion (W7DJ).  Steve and I have since suggested some revisions in the TNØ7 instruction manual, as some of the terms were a bit unclear. This happens frequently when manufacturers are using words that they understand, but which the ham user is unfamiliar with. 

First impressions upon unboxing: My first comment was "Man, this thing is built like a tank." Each of the components appeared to be the best-in-class, from the mast to the Impedance Matching Device (the "IMD-105" as it is referred to by TNØ7). The IMD-105 keeps the SWR at around 2-to-1 on most frequencies, allowing touch-up tuning by your transceiver's built-in antenna tuner. It's built into a high quality metal enclosure, certainly weather resistant but also not easy to open it up and check out how it is built. Steve's first comment was, "Beautiful shiny green color, but I wonder how easy that gloss coating will be scratched?" He's right . . . it's a gorgeous hue, but scratchable. I'm sure the color helps it fit right into the surrounding trees if you're in a wooded zone. For us (in Arizona) it's not quite the right color for blending into the cacti. It's spiffy, though, to say the least!

Assembly was easy, but it required a call with Bob at TNØ7 due to the confusion we had about the labeling of components. A knife-edge wire connector was labeled a "thimble," and we didn't "get" that the wire that goes through the center of this 32' mast would be drawn into the antenna automatically. You should have seen Steve trying to push this wire down the length of a 32 foot antenna! Hilarious that two grown men, both experienced hams, didn't see the beauty of what Laura and Bob had designed . . . one phone call and we reversed our process, extending the mast first and we both watched as the wire was drawn up into the antenna on its own. Voila!

This thing is tall, and very sturdy. It stands 32 feet, and while it is fairly slim at the top, its strength is apparent. (It collapses down to 4'). TNØ7 suggests that you can use it either on its own, or with radials, and also sells a 35' wire extension that attaches to a connection point at the top of the antenna. From there, you can run it as a sloper or bring it over to a tree at 32 feet tall which results in an Inverted L shape. In my location, I've got nothing 32 feet tall, so we ran it on its own and also as a sloper. (Well, there is a 40 ft. cactus nearby but that is a mighty risky proposition.)

We found the SWR to be between 2.0-to-1 and 2.2-to-1 across all of the bands from 6 down to 80, and for our testing worked QSO's on 40 and 17 meters. The "Impedance Matching Device" was apparently doing it's job because the built-in tuner on Steve's radio brought it almost instantly to a flat SWR. With later testing, the antenna's propagation seemed to be mostly unidirectional, but upon applying the top wire and stretching it down to about 2' off the ground in a sloper configuration, it became a bit more directional. The noise floor with this antenna was remarkably low for a vertical! 


Marty Wood (N4AMW) is a POTA activator extraordinaire and a retired electronics engineer. He told me that he's super impressed with the SFP-102, and that he's had much better results than with the Wolf River he'd been using prior to last October. Marty uses a trailer hitch mount and the TNØ7 35' extension wire in either a sloper or Inverted L (see photo). 

"There's no way I'd give this up," Marty says. "I've had over 8000 QSO's since I started using it in October. I'm getting out to Spain and South America frequently, and on a decent radio day I can work 60 to 65 POTA contacts an hour. It's been a terrific investment so far." Marty is using an FT-891 and generally works at about 75-90 watts on SSB.

The antenna can be purchased without the IMD-105 but it then requires an external tuner. However, in that configuration it is then capable of full legal limit. Marty agrees with me that it's nice to be able to take a radio like his or my IC-7300 and use it at full power at a POTA location (antenna rated at 100W SSB in that configuration with Impedance Matching Device). With the responses this antenna is capable of getting for you, that's an easy POTA scenario and fine for 99% of POTA operations. Deployment or tear-down takes Marty about 10-20 minutes, depending upon the amount of radials he brings along. For my testing, I've only used one or two radials but Marty has used 6 or more with great effectiveness.

It took Steve and I about an hour for the initial assembly which should have taken substantially less time. We're two old friends who hadn't seen each other in a while, so there was a lot of chatting and discussion along the way. There's nothing better for bringing old friends together than putting together an antenna!

The SFP-102 sells for $279.95, and optional accessories such as the excellent TNØ7 drive-on mount or trailer hitch are available from their website. Some amateur radio dealers also stock and sell the SFP-102.  I rate this antenna with a solid A+ for build quality and A for user experience. We'll be doing a big article on POTA activations later in May -- I expect the TNØ7 flagpole to be a major part of the action. Stay tuned!


A Book of Advice for Fun with Ham Radio

Bob Witte (KØNR) is an interesting ham. He is an electrical engineer and author of a number of technical books. He's a credentialed fellow, with a BSEE degree from Purdue University, an MSEE degree from Colorado State, and leadership experience from Hewlett-Packard and Agilent Technologies among others. Bob's recent book was a hit here, so I went back to read an earlier one he wrote for the ham market in 2019. (You'll find my review for his excellent Extra Class License Manual written along with Stu Turner of Ham Radio School, at this link.)

In my earlier review, I noted how Bob's folksy style makes it easy to understand complicated subjects. I like the way this guy writes, and his first book for the radio operator, VHF, Summits and More, reflects that same writing approach. The book is subtitled "Having Fun with Ham Radio." I think he probably would have sold a lot more books if he had switched the title and sub-title . . . that's because the book is really intended for the rather new ham, someone who may have recently been licensed and is presently active on VHF, perhaps with a Technician Class license.

Still, I've been licensed for years and I found content in this book that was new to me -- most notably from Bob's excellent section on "Summits on the Air." Unfortunately, there's really no POTA information in this book, but a lot of what you learn from Bob about operating from a Summit can be used in a park setting as well.

There are three sections in the book. For one, a general introduction to VHF/UHF operating, with great info for the newcomer on repeaters, SSB on 2 meters and more. Some of this comes from Bob's blog, which is KNØR.com, but there's a lot of new material here as well. The second section is a selection of Bob's hits from his Blog, and then the final third focuses on the SOTA activities which are so plentiful in his native Colorado.

The book is available on Amazon.


73 for now,



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Dave Jensen, W7DGJ

Dave Jensen, W7DGJ, was first licensed in 1966. Originally WN7VDY (and later WA7VDY), Dave operated on 40 and 80 meter CW with a shack that consisted primarily of Heathkit equipment. Dave loved radio so much he went off to college to study broadcasting and came out with a BS in Communications from Ohio University (Athens, OH). He worked his way through a number of audio electronics companies after graduation, including the professional microphone business for Audio-Technica.  He was later licensed as W7DGJ out of Scottsdale, Arizona, where he ran an executive recruitment practice (CareerTrax Inc.) for several decades. Jensen has published articles in magazines dealing with science and engineering. His column “Tooling Up” ran for 20 years in the website of the leading science journal, SCIENCE, and his column called “Managing Your Career” continues to be a popular read each month for the Pharmaceutical and Household Products industries in two journals published by Rodman Publishing.

Articles Written by Dave Jensen, W7DGJ

This page was last updated April 23, 2023 00:01