We are blessed to live in a central Florida community that has miles and miles of “multiple mode” paved paths which we enjoy daily for trike riding. Our recumbent TerraTrikes are nearly 20 years old and one of the best purchases we ever made. Maybe I can go play radio on mine.
Let’s make the trike radio-active
First the antenna… The Elecraft AX1 has a reputation ranging from “outstanding” to “dummy load.” My experience has shown it very capable when set up well. It’s not for worldwide DX, but for pure fun, and indeed offers fun for POTA activities. Let’s deploy the AX1 on my TerraTrike.
There is a tripod mount widget for the AX1 which fits the standard camera 10-24 screw. I drilled and tapped a 10-24 hole in the deck of the trike’s panier carrier, and used a hardware store bit of 10-24 threaded rod to hold the antenna. My first attempt was with a short stub a few inches long. I learned later that the antenna was happier being elevated, so the remainder of that rod, 36″ minus the short stub, leaves a 32″ rod. Add a couple of nuts and we’re have a 32″ tower. Mount the tripod widget atop the threaded rod and the AX1 to the BNC connector there. Add 5.5′ of RG-316 coax, 13′ counterpoise wire (simply thrown on the ground under the trike), and some “secret sauce” to make an operational 20M antenna.
Some complain that the AX1 doesn’t work, is just a dummy load. My opinion is that these are the people who don’t understand antenna characteristics beyond reading the advertising hype. They break open the package with “plug-n-play” expectations, or with “my tuner will take care of it” expectations. Some don’t know how to test or adjust their antennas and end up disappointed.
Base loaded vertical antennas are sensitive to radiator length and ground conditions. Those with short whips have especially narrow bandwidth, often covering only a portion of the band they are designed for. Getting them to work at the frequency you want means you need to be very finicky about radiator length.
My secret sauce enables using this antenna with NO tuner. It works because I’ve measured the antenna’s behavior and know the AX1 naturally resonates at the SSB, not CW, end of 20M, or actually beyond in many deployment scenarios. To get resonance down to the CW portion of the band I add a 8″ extension via an alligator clip. Careful adjustment of the whip length then brings it to a beautiful not too steep SWR null.
Along this line, Linus Ly2H advocates using a capacitance hat to moderate the antenna’s reactance component. I’ve tried his suggestion and agree that it helps broaden bandwidth, flattens the curve somewhat. Yet, I find that it also raises the null point up to the 1.5 neighborhood.
I’ll stick with my clip-on extension and this result.
Next, operating layout… I’m not carrying a collapsible table or folding chair on the trike. I prefer sitting in the trike’s seat. But, where to put the gear? My DIY arrangement is made from a simple plastic kitchen cutting board, with a few washers epoxied to it, with a hook and loop patch for holding the Talentcel 3000 mAh battery and QMX radio, and with a non-slip pad to keep my phone in place. The QMX has an absolute voltage ceiling of 12v. So, the blob in the power cable is an inline voltage regulator. I use the wonderful Ham2K PoLo logger on the phone. Some CWMorse keys have magnets built in. The one I’m using did not, but I added them and it now sits nicely on those washers.
Transporting… is easy. The trike has two panier bags, into which I can stow the board, the threaded rod and a couple of Maxpedition pouches which hold the AX1 and the QMX, and other things I might want while riding. …and for places beyond a reasonable trike ride from home, I have a pickup truck that carries both of our trikes.
Note well: NONE of these product links are affiliate links. I don’t need to be making money off of my fellow hams’ interests.
End result… so far… My first tests were from the driveway at my home. Mid morning (14:00z) on 20M isn’t the hottest time of day for the band, but I set up and casually completed 3 hunter QSOs, while fiddling with the antenna in between. Twenty minutes, 559 and 599 RSTs from KY, PA and NY.
That’s a great start for an experiment with a dummy load.
Cool setup, Bob!
Thanks Craig.
Note to self… I tried elevating the radial at one point and saw much higher SWR. John VA3KOT tells me why in his article about a “Band Spanner” antenna:
“A lesson I learned early in my ham career, but overlooked in this exercise, was that a short-loaded, high Q vertical whip requires a carefully tuned counterpoise – or a good ground. Simply using a raised 17ft wire isn’t good enough.”