Power Source for Handheld Gadgets

My handheld radio setup worked well, but ate batteries. I averaged 10 transmissions before there wasn't enough power to push out (I could listen for a few hours).

So back to the web boards and Google. I found several posts about using a SLA battery as an alternate power source.

An SLA battery is a sealed battery most often used for backup power in emergency lighting. The package is reasonably small and dense, so it doesn't take much room in the tiny cockpit. (more about batteries here) I ordered a 12v from Radio Shack for $27.

The next challenge would be connecting the battery to the Handheld radio. After some research, I decided to use a 12v power adapter (like this). I'd make a female attachment from the battery, then plug the male end into the battery that way (and connect the radio power supply via the small plug).

I removed the alkaline battery pack from the radio, plugged everything in and -- success! I could hear transmissions on the handheld.

I zip tied the loose ends, applied Velcro to the bottom of the battery (so it would sit on the floor carpet) and carefully ran the power supply line along the glare shield.

I took a few test flights and am amazed. The radio performs as well as a panel mount and I have no real limit to total transmissions. I flew to Clarion and back through PIT Class Bravo and maintained contact with PIT Approach there and back with no problems.

My next project is attaching a small solar trickle charger to the battery to help maintain charge on longer flights. I should also be able to power a handheld GPS through this setup.

Handheld Radio Antenna Mount

Although I’d prefer to fly NORDO and use pilotage to get from A to Z, we live in more crowded, complicated times. That coupled with a hangar opening at a Class D airfield meant I needed 2 way communications on board my 1940 65-LA Chief (with original serial number O-145-B2 Lycoming engine).

I’d used a Sporty’s SP-200 handheld from the air before (once as a student pilot when I lost all electric in a C152 flying from KVVS to KLNS, and another time IFR in a 1947 V-tail Bonanza). I could hear them and they could hear me, so I figured it would work in the Chief. But I heard “Unreadable” more than I heard my tail number, even with an antenna extension stuck to the windscreen.

So after querying the email list and a few web boards I decided I’d install a whip antenna. I ordered the “Quickie Antenna Kit” (two BNC connectors, some RG-58 coaxial cable, torroids, copper tape), a 2'x2' 6061T6 .025 sheet of aluminum, and a straight VHF whip antenna from Aircraft Spruce.

I planned on installing the whip behind the baggage area. However, once I looked it over I realized the maze of tubing would severely attenuate the signal. I’d have to mount the antenna externally. This Chief is not a pristine show plane (by any stretch), so I choose function over form.

Materials

·      6’ Length RG-58 Coaxial cable

·      1 Male BNC Connector (to connect cable to radio antenna port)

·      1 ½” diameter ring terminal

·      Liquid tape

·      Solder

·      RTV Sealant

Tools

·      Adjustable wrench

·      Knife or diagonal wire cutters

·      Soldering iron

·      ½ “ metal drill bit

·      Drill

·      Screwdriver (to remove wing root fairing)

·      Multimeter (I bought mine at Ace hardware for $13)

The wing root faring material is too thin to support an antenna, so I reinforced it with a 2" x 6" strip of .025 aluminum as a doubler. I measured and re-measured, then grit my teeth as I drilled a ½” hole through the wing root fairing about 18” from the trailing edge. It took some work, but I finally had the doubler mounted in the gap between fuselage and wing, the wing fairing over that, and the antenna through a hole in each.

I fed the coaxial cable down in between the lower wing root fairing and the fuselage and then though a gap in the rear window seal.

On the antenna end, I stripped the coax and terminated both the center wire and the ground shielding (which in RG-58 is wire mesh, not foil as used on TV coax) with ring crimp-style terminals. I soldered to fill in the gap and ensure security of the terminal to each wire. I kept the two ends about 1 1/2" apart, and then insulated all remaining bare wire with Liquid Electrical Tape.

At the other end I tried to install on the screw-on BNC connector but no joy – it would not fasten no matter how many times I tried. I was running out of cable to cut and try again so I decided to get a better BNC connector from Radio Shack.

After a couple of trips to Radio Shack to get an RG-58 connector (be sure the connector is meant for RG-58. A RG-56 connector will not work), I completed the connection and took the airplane out on a test-taxi. Ground and Tower could hear me – as long as I was angled in certain ways towards the tower. In fact, I was unreadable when at the end of the taxiway for 18 –hardly a suitable situation.

After another round of questions on the board Bill Pancake and Peter Lapthorne both suggested it may be too close to the trailing edge. I decided to bite the bullet and drill another hole in the wing root fairing, this time close to top dead center. This reduced the length of the Coax run from 6' to 3', and provided a longer ground plane in each direction. Just for grins I stuck the 4’ length of copper tape that came with the quickie antenna kit to the underside of the doubler and the fairing. I checked and re-checked continuity and all was as expected.

I tightened everything up and sealed it with RTV. It ended up being a better solution since I was able to reduce the coax cable run to 3’. After doing complete multimeter checks, I rolled it out of the hangar and radio checked with ground and tower. All was loud and clear with no engine noise (I was still able to hear transmissions with squelch turned up quite a bit). I took off and headed north and could hear AWOS clearly 25 miles out. Then I transmitted to MGW tower and he heard loud and clear 15 miles out. In my headset it sounded as if I was in an airplane with a dedicated panel mount Comm system!

The standard Rayovac Alkaline AA batteries lasted for the dozen or so transmissions I made on the ground, in the air, and back on the ground after landing.  Direction of flight did not affect reception or transmission. I did not try to listen to 122.8, but my guess is I would hear the same amount of traffic as I would in an airplane with a panel mount.

I wish I’d kept a list of all those that provided advice and guidance, but I didn’t. Nevertheless, please accept my sincerest thanks!