Optimizing the HF Alpha MOTO Antenna

HF Mobile with the Alpha MOTO

First, I wish to tell the nay-sayers that this is not a simple Balun system. It is not a cheat of some kind.

It is a special matching network that works to complete the antenna system using a properly grounded/bonded counterpoise. Currents are balanced with the Alpha Match. This tuning/matching system bonds to the vehicle. This allows RF current to balance a well bonded vehicle. The vertical element radiates very well against the body. Think of the vertical element SORT of like an end-fed non-resonant wire antenna that uses a vertical whip.

102″ whip test

The HF mobile antenna tuned okay on 40/20/15, but really bad on 17/12. 10 was nearly perfect. While it worked okay, I found places where RF return currents would cause cut outs. So, the 102-inch whip was forcing RF into the coax shield more. Not good. Saw this on occasion using 17-foot MFJ whip on a handful of spots mainly on 20/40.

98.5″ whip test

Cut whip to 95.5″ with total length including spring to be 98.5″, or 2.5m long. Noticed better tuning on WARC bands and bad spots on some regions of 10m (lower portions below 28.3). 20m Was decent but had two “cut out” locations. 40m was fine. 15 was decent but not ideal (no less than 1.6:1 SWR in most areas.

2.25 meter whip test

I stopped and remembered my chat with Steve at Alpha Antenna and about a good compromise length of 2.25m for HF mobile deployments. That would be 3/8 on 6m, 3/16 on 12, etc. I cut down 102 whip, to 7.5-foot (88.5″ total, 2.25m). Binding critical regions of my 2013 Ford in progress, and 25 feet of LMR-240.

Results

During the last two days, all I can say is WOW!!! This HF mobile antenna tunes all bands in the 40-10 region VERY well, best on 40/20/15/10, but also very good (<1.4-1.5 SWR on whole band) on 12/17. Lower on 12m and upper on 17m best.

I began operating under fair to good conditions. I received a 58-signal report from Costa Rica! Then Italy at a 57 on 17m, Brazil and Chile at 56/57 on 20m. Next up was Slovakia at a 56 with heavy QSB on 17m! I am doing significant DX call-ins without much extra effort over my stationary setup with 250+W and a 60-foot sloper!

I’ve had significant results with the setup and refinement that I sent at least a dozen folks to Steve at Alpha for this fine product offering. What I prefer with the Alpha Antenna MOTO is a clean, sleek line look with a simple whip. I did not like the rather beefy look of all other mobile HF antenna systems. The MOTO gets out, looks good and is multi-functional.

73 – VE4VE

Credit for the content goes to VE4VE (ex VE4DL)

FROM ALPHA ANTENNA

– While your vehicle is parked, enhanced coverage and performance from 10-80 meters can be enabled by placing a 60-foot wire at the top of the match then tying it off at the other end to some support or even staked (but insulated) at a ground stake.

MOUNTS – We do not recommend using a lip or magnetic mount, because losses on 40M and even other bands become too great when a direct surface mounting hardware is not used. If you do end up using a magnetic mount, then the widely available Tri-Magnetic Mount should be used to increase the safety and capacitive grounding of such a mount. Just note that you will need to cut the coax off and short the braid to the center conductor of the coax for magnetic mounts in order to complete the path to ground.