Using a handheld radio in a Piper Cub

[The following was posted to the Piper Cub Builders List by Lynn Towns, and is posted here with his kind permission -- Dan Ford]

When I first started flying (33 years ago), I had a couple of Stinsons, and I had quite a bit of trouble with the radios (vacuum tubes and crystals). Then, I bought a Champ (more fun) and liked the simplicity of no radios. I flew the Champ, and then my PA-11 Cub for about the last 25 years without any radios. I used earplugs, and I had a Hush-a-Com intercom.

During the last winter, I started to plan a long cross country with a friend of mine who also owns a PA-11. He encouraged me to get a radio so we could communicate on the trip. I didn't immediately agree, but I finally decided to give it a try.

I bought an ICOM A23 handheld, and I originally tried using it in my Cub without a headset, and with the rubber ducky antenna. I bought a RAM adjustable belt clip mount model# RAM-B-149-BC1 to attach the radio to the windsheild tubing near the throttle ($28.80 from Aircraft Spruce and Specialty). The mount worked great, but I couldn't hear the radio at all while I was flying.

Then, I bought a Lightspeed 25XL ANR headset. The ANR curcuit on the headset emits RF signals that were picked up by the radio antenna, making reception garbled. My friend said my transmission was fine. I exchanged the Lightspeed headset for a Pilot Avionics PA 17-79 DNC XL headset. After posting my problem on a newsgroup, other newsgroup members responded who had experienced the same problem. Several solved their problem with the Pilot headset. This system worked OK, but the range of transmission/reception was limited pretty much to the pattern; I would estimate 5 miles maximum.

MY PA-11 friend suggested an external antenna. He had been using a 1/4 wave whip antenna mounted on the wing root fairing with his ICOM. I believe he was getting 25 or 30 mile transmission/reception. I did some research, and decided the wing root fairing was not an adequate surface area for a ground plane, making that kind of antenna inefficient. A folded dipole antenna that does not need a ground plane seemed like a better choice.

I bought an Advanced Aircraft Electronics VHF-5T folded dipole antenna (www.advancedaircraft.com) ($117.95 from Aircraft Spruce and Specialty) and installed it vertically on the left side of the fuselage fabric with duct tape. I was able to slide it between the side fuselage tubing/stringers and the fabric. The bottom end butts into the lower longeron, the upper end curves inward in the upper fuselage just below the stringers, and the antenna ends just past the top center wooden stringer. It is centered fore/aft in the second bay of the birdcage behind the baggage compartment. My mechanic said it is not considered a permanent installation, so no 337 is required.

The ICOM radio has a BNC antenna connector like the antenna, so a few feet of coax finished the installation. There is extremely low loss without any adapters required using the ICOM handheld (unlike some handhelds that do not use BNC connectors).

The performance is better than I ever dreamed. I regularly hear pattern traffic from airports 100 statute miles away, and I once heard someone that was approximately 200 statute miles away across flat land. I have transmitted to towers 50 statute miles away, and they said I was "loud and clear". I really don't know the limits of the transmission/reception distance, but it is more than adequate.

I'm convinced that this antenna installation is superior to any 1/4 wave ground plane antenna on a fabric covered plane. Besides, it is inside the fuselage where it doesn't show.

I was very happy with my communications capability, but my handheld also has a VOR receiver, and that didn't work too well using the vertical antenna. I reasoned that since the VOR signals are horizontal, I could add a vee-shaped horizontal antenna to get good VOR reception. So, I bought another Advanced Aircraft Electronics antenna and installed it in the birdcage, in a horizontal vee-shape with the open side facing forward, in the first bay behind the baggage compartment. I mounted it on the fuselage tubing using balsa wood and nylon cable ties.

Since the ICOM only has one antenna connector, I wanted a way to switch between the two antennas. I posted on a newsgroup again, and got a suggestion from a pilot/ham operator. At his suggestion, I found and installed a Dow-Key (>.1 db insertion loss) coaxial switch to easily switch between the two antennas.

The results using the vee-shaped antenna were mixed. Something (probably the engine/prop) partially blocks the signal from the front, and the forward VOR reception is only about 20 miles. Anywhere behind the wings it is 40-50 miles, so it works well going from a VOR, but not as well going to a VOR. My main purpose in having it was to be able to duplex to Flight Service Stations, so I can always temporarily turn if I have to. The VOR also provides a backup for my GPS, but I have yet to use it for navigation.

Surprisingly however, the horizontal vee antenna works very well as a communications antenna. Communication range with the vee-shaped antenna is at least 50 miles. In fact, it works better than the vertical antenna when communicating with someone directly above or below me (which often happens in the pattern). If I was going to do it over again, I would only install the horizontal vee antenna and eliminate the other antenna and the selector switch.

I eventually bought another Pilot 17-79 headset and a Pilot PA 200-A23 intercom that plugs directly into the ICOM radio (doesn't require a headset adapter, and comes with a velcro mounted PTT switch). Using the intercom with matched headsets does not require separate squelch controls for each headset (this may become a problem with unmatched headsets). Intercom volume is adjustable separately from the radio volume.

I am completely satisfied with this system. I think the folded dipole antenna makes a handheld radio have equivalent performance of just about any panel-mount radio. And, you can install the entire system yourself. The only improvement I can even think of would be an increase of forward VOR range, and I think that would require a VOR antenna mounted somewhere outside of the fuselage.

Last spring, my PA-11 friend and I took our 73 flight-hour, 16 day cross-country in our planes (Michigan to southern California, up to Oregon, and back). It was great fun. My headset was comfortable for the entire time, and the only problem I had with my radio is that twice I transmitted too much and the rechargeable battery went dead. In September, ICOM finally came out with an alkaline battery pack for the A23. I have had one on order for 2 months, but I still haven't gotten it.

Now that I have a radio again, I feel safer. I have a better idea who else is in the pattern, and where they are. It is comforting to know I can call Flight Service in marginal weather, and the headset makes flying quieter, more comfortable, and less fatiguing. So far, the dependability of the radio has been very good. I'm a happy Cub pilot!