Metrocrest Amateur Radio Society
News
September 6, 2021
The Chameleon Inverted Delta Loop Antenna
—Kevin Grantham, N5KRG
Chameleon Antennas makes a variety of portable antenna kits based on military models. With few exceptions all of the components are made in the USA. Various components are combined into different kits with different performance characteristics. One of the newest antennas they have produced is the inverted delta loop, model CHA TDL. This antenna won a US Army HF Low Power contest recently—details are on the Chameleon Antenna™ website.
Andy Parcel, KE5KOF, and I decided to try this antenna out. We already had many of the pieces—Andy has the Tactical Dipole kit and some extra bits, and I have the Multi-Purpose Antenna System (MPAS).
The inverted delta loop antenna starts with the ground spike—a heavy-duty steel spike with a 3/8-24 threaded hole in the top and a radial wire attachment point on the side. Chameleon says to leave 8 inches sticking out of the ground.
Unique to the inverted delta loop is a machined metal disk with a male 3/8-24 threaded post on the bottom, two 3/8-24 threaded holes on opposite sides, a 3/8-24 threaded hole in the top, and two 3/8-24 threaded holes on the beveled sides. This is threaded into the top of the ground spike.
The Chameleon Hybrid-Micro (comes with the MPAS and other kits) fits one of the holes in the beveled edge. The Hybrid-Micro is a 5:1 transformer in a Delrin case with stainless steel mounting hardware on each end.
Two stainless steel 17-ft whips (Chameleon part number SS17 but MFJ-1979 works as well) are attached, one to the top of the Mini-Hybrid and one to the other hole in the beveled edge. This forms a large “V” shape.
Finally, a 25-ft wire with copper alligator clips on each end connects the end of each whip together. Chameleon supplies their PTFE coated copper-clad steel wire on a winder for this purpose.
This arrangement should work from 80-10 with an external antenna tuner. Worst case SWR was 5:1 so internal antenna tuners may not be able to work with it, other than the Xiegu G90 or HPA125B, for example.
So much for the instructions. We saw in the fine print that it would work better if elevated. Some email exchanges with Chameleon tech support revealed that they had tested it only to about 10 feet—they also cautioned that wind loading would make it unsuitable to mount atop Chameleon’s own Military Mast Extension unit. We decided to attach it to the top of the Long Buddipole™ tripod. This has an NFT pipe thread to go into the Buddipole VersaTee™ but also has a 3/8-24 threaded hole. AHA! We screwed the machined disk into that and used the Buddipole guying system and raised the base about ten feet.
We surmised that ground coupling was why Chameleon mentioned raising the base. Also, the ground spike and metal disc are an electrical path to ground, but the plastic Buddipole tripod isn't. More practice will help us understand the effect of ground coupling.
The antenna really wants to “windmill” across the wind, but because this was Field Day we didn’t care where the contacts came from. It is only mildly directional. It performed well on all bands we tried. We even tried 6 meters and it worked there, too.
Andy put up an inverted V for 20 meters. We compared the two antennas on 20m and the Chameleon Inverted Delta Loop was at least two S units quieter while hearing even more stations.
We were very pleased with the performance of the Delta Loop and plan to have it out on weekends and other events. It folds up very compactly—the whips and ground spike are about 24 inches long, and the machined disc and the wire winder easily fit in a small bag.
All of the Chameleon Antenna configurations that Andy and I have tried so far work well. Some, like the Inverted Delta Loop, go up and down very quickly and take very little area—they also don’t require trees or poles. Other configurations take longer, take more ground space, and require more supports. Some are NVIS (close in, 50-200 mile HF range), some are DX, some are intermediate, and most vary by the frequency being used. Because at lower frequencies they are “short” for the wavelength, they aren’t the best for long DX although we have made contacts to Okinawa and Hawaii on some configurations.
We highly recommend Chameleon Antennas and the Inverted Delta Loop.
73, Kevin