When I finally invent a time machine, I'm going to grab a baseball bat and then
go back about 100 years. Mr. Marconi had better watch his step. After nine
years of owning Moonraker, the biggest sources of heartburn has been fighting
the radios.

When I bought the plane, it mounted a Narco Escort 110 radio that transmitted
clean and received signals from a long way away. Unfortunately, the FCC
upgraded the frequency accuracy standards, and it became illegal to transmit
using the 110.

I bought a used Narco Escort II from a friend. It worked for about a week, then
broke. Not the radio's fault, I think... the generator system had been
suffering some problems, and I think the radio got fried by overvoltage.

$300 later (exactly what I'd paid for the used radio, in fact) it was
operational again. It worked fine for several years, then started acting up
again. Narco radios use separate receive and transmit antennas, and I noticed
that folks couldn't understand me if antenna "A" was hooked up to the transmit
side, and I couldn't hardly hear anyone else if I hooked up the receive side to
that antenna.

So I built the what I called the "CW McCall's Revenge" antenna from Radio Shack
and Home Depot parts, and things were OK for another year.

http://www.bowersflybaby.com/stories/antenna.htm

Then folks started having trouble understanding me again. I flipped antennas,
but folks still were complaining that they couldn't read me. Finally, I decided
that I was tired of fighting it. It was time to replace the radio.

However, I had some limitations. First, my avionics box tends to restrict the
size of a radio that I can mount. It has only room for one "full width"
avionics box. It was currently occupied by the Escort II (which mounts in a
3.125" instrument hole) and my Microair Transponder (which mounts in a 2.5"
instrument hole):

http://www.bowersflybaby.com/tech/avionics_box.JPG

I really needed a NARROW radio...a standard 6" wide box wouldn't leave enough
room for the transponder.

My second limitation was cost. The only other type of radio I'd found that fit
in the 3.125" round hole was the Becker and they were over $1,000. The ICOM
IC-200 panel-mount radio is full width but very flat; sketching out the problem
indicated that I might be able to put the transponder on top of the radio...but
it would be a close fit. The ICOM IC-200 was still about $800.

Finally, my last limitation was readability of the display. I've got the
Microair Transponder. It seems to transpond just fine, but the display is
*very* difficult to read. It's a pretty tiny LCD screen on the front of a
sub-miniature instrument. So I was leaning away from the Microair comm radio.

The solution was pretty clear: a handheld radio. The price is right ($300 or
less), and the RF output is pretty close to an in-dash type. The one drawback
is that I prefer a panel-mounted radio. But I could just as well give a
handheld a try.

I went to American Avionics at Boeing Field and shopped for handhelds. I bought
an ICOM IC-A5, a *very* tiny radio. Without the rubber duckie antenna, it's
barely 4" tall. I paid about $230 for the radio with a NiCd battery pack, and
another $60 for the adaptor that would let me plug my regular headset into it.

A new toy. I *did* have fun, before I took it out to the airport to try it on
the plane. I live on a hilltop overlooking the airport, and the Unicom has the
"superunicom" feature where three mike clicks transmits the current airport
conditions, and four mike clicks lets you do a radio check, where it records
your transmission and retransmits it after a delay. I determined the radio
worked fine, just fine, from the hilltop.

I did find one funny glitch, though: When I plugged my headset in and used the
push-to-talk (PTT) switch on the radio to transmit, the output of BOTH my
headset mike and the built-in radio mike was sent.

The headset adaptor included a jack for a remote PTT switch. I decided to go
ahead with a temporary install and trust that when the remote PTT was used, the
on-radio mike didn't activate. Later tests confirmed this.

I went out to the airport, stuck the handheld in my pocket, and taxied Moonraker
to the ramp near the airport office and the Superunicom station. I tried the
"Radio Check" feature with both the handheld AND the aircraft radio...and the
reply transmission from the Superunicom sounded about the same.

Hmmmm. I decided to install the new radio completely separate from the aircraft
systems, then try it with the aircraft antenna to see that's where the problems
were.

The next day, Saturday, I went to the airport to do a temporary install. As Fly
Baby drivers immemorial have discovered, the little shelf where the Master
Turnbuckle sits is an ideal location for a handheld. Mechanical installation
was pretty simple... a nylon tie-wrap around the turnbuckle, through the plastic
loop on the back of the radio where the belt clip normally goes. It left just
enough room for the battery box of my ANR headset, which uses a velcro strap to
tie onto the flat landing wire terminal strap.

The headset adaptor took up a lot of space between the wire terminal and the
instrument panel, especially when the headset cables were plugged into the
jacks.

As I was leaving home, I realized I still needed that remote PTT switch. I dug
through my electronics scrap bins and fold an old, OLD doorbell switch. It was
an all-metal "button" style. I'd bought a 6' audio cable with two 1/8" jacks at
Electron Hut, and after snipping a foot off one end, the button was quickly
wired up. All it needed was a little duct tape to insulate it...and the closest
roll on my workbench was bright yellow.

A couple of tie-wraps and we were ready to go. I'd left the rubber duckie
antenna, so there were no electrical connections to any aircraft system.

Wild blue yonder time. I started the engine, then reached to the headset
battery box to turn on the ANR function.

The radio broke squelch...and no amount of adjustment would get rid of it. It
looked like the proximity of the ANR circuitry (in the battery box) with the
radio's rubber-duckie antenna was inputing some noise that the ICOM couldn't
handle. I had to turn off the ANR.

I did a radio check while taxiing out to the runway, and the Superunicom
recording sounded fine. We launched, and I did the four mike clicks on downwind
to check. After the readback, some kind soul transmitted, "Fly Baby, you sound
fine." The one problem was the audio level. I could hear things properly, but
had the volume setting at maximum. If I could run the ANR, maybe the volume
level could come down a tad.

So...back to the hangar. Time to tie the handheld into the aircraft
antenna...hopefully, using an antenna well away from the ANR box would stop the
interference.

I was going to hook up the radio to the "CW McCall's Revenge" antenna. I put a
right-angle BNC fitting atop the radio, and ran a new coax down to the end of
the cable from the antenna, tying them together with a BNC connector.

But...heck, I guess I should check out the antenna, first.

I touched an ohmmeter to the ground plane and then to the metal shell of the BNC
connector. Infinite resistance.

Oh, HO!

The ground plane (aluminum foil on the baggage shelf) connects from the
antenna's BNC connector to one of the anchor lugs on the antenna mount....see:

http://www.bowersflybaby.com/stories/ant2.gif

The shell at the antenna connector was grounded, so it was loosing connection
between the connector and the ground plane itself. I tightened the mounting
bolts for the antenna...and the ground plane showed good.

I thought for a moment. Maybe that was all that had been wrong to begin with.
I crawled back in the airplane and reconnected the antenna to the built-in
radio. I buttoned-up the belly plate and started to put the turtledeck back in
place.

Hmmmm...maybe one last check of the ground. The braided ground line for the
receive antenna runs close to the foil ground plane. I touched the ohmmeter
between the two.

Nothing. Damn, they *have* to ground to each other...each attaches to the case
of the radio. I decided to ground the foil to the braid with a separate wire.
I got one side installed, but then had a fit of conscience. Damn it, I wanted
to *solve* the problem, not kluge a way around it. Besides, having two separate
grounding paths to the foil is a classic setup for ground loops (the electrical
kind), even worse when one was apparently intermittent.

Time to pull the antenna. I'd designed it to be easily removed from outside the
aircraft, with both mounting lugs including nut plates. The ground plane
connected via those anchor plates. Since the plates weren't really intended for
electrical functions, I suspected that perhaps some corrosion in the plate or
the cad plating flaking off the bolt was disrupting the electrical path. The
best solution would be to replace one of the nut plates with a conventional bolt
and a grounding lug.

The antenna came off quick enough, and the anchor nut came off easily. As it
did, the ground wire to it popped free. Looks like I hadn't soldered it
properly...I seem to recall having problems getting the nut plate hot enough.

Anyway, since the plate was off, I went ahead with the new ground lug. Install
it back in the airplane, test carefully with the meter, the button the airplane
up to go fly. I snipped the ICOM free and mounted up. I figured that was
it...the radio will work, and I'd have a sweet little handheld to listen to when
I was working in the hangar or strolling around the airport.

After takeoff, I punched the mike button. "Fly Baby 848 departing pattern to the
west."

"Aircraft calling, you are unreadable" came the instant response.

Well, pooh.

My time was up that day, so I tucked the airplane into the hangar for the night.
It obviously hadn't been the antenna. It *might* have been the coax from the
radio to the antenna. I use pre-made coax cables bought from the a electronics
store (not Radio Shack, but another place that caters to hobbyists and hams). I
use two cables on each antenna run to make it easier to swap the transmit and
receive antennas. I'd checked out the cable that ran from the connector to the
antenna...but the cable from the radio to the connector could be the bad one.

Back to the airport, next day. I brought a new piece of test gear with... the
old Escort 110, which I'd rigged up with a power supply and an antenna to listen
to traffic in my den at home. I also brought a small tape recorder so I could
listen to my transmissions when I returned.

I connected a brand-new cable from the back of the mounted radio and ran it
vertically to the instrument panel. There, I used a connector to the "rubber
duckie" antenna from the ICOM and tie-wrapped the antenna in place. It was in
about the same spot as well I ran the handheld the day before.

I turned on the desktop radio and tuned it to an unused frequency. I cranked up
the airplane's Narco, and hit the PTT switch. "Test, one two," I said. I could
hear my voice from the desktop radio across the hangar.

Well, heck. It seems to work. I rolled the plane out of the hangar, turned on
the tape recorder by the desktop radio, mounted up, and took a single trip
around the pattern.

As I taxied by the airport office after landing, I saw my buddy Athol standing
outside with his handheld. He knew about my radio problems. He held
thumbs-down.

At the hangar, I listened to the tape. I could hear the radio cutting out...not
distorted, just like it couldn't seem to break the squelch of the receiver.
Other aircraft's radios came in just fine (amazing, since the receiver was
operating inside a locked metal hangar).

I decided one last-ditch trial. I switched to a different headset, in case the
mike on my Flightcom was bad. I didn't think that was the case, since the
sidetone (your own voice over the headset when you transmit) was normal. I
punched the record button and launched again.

"Sounded real scratchy, Ron," said Athol as I taxied back. I listened to the
tape. One transmission, my base-to-final turn, actually sounded all right. But
that was the closest point to the hangar where the radio was. If the Narco
output power was low, that would explain many of the problems...those with
squelches turned to the minimum would hear me, but those who liked to keep their
squelches well up would hear me cutting in and out.

So, time to try with the ICOM again. I tie-wrapped it in place again. I
connected the aircraft antenna to it, hoping the interference with the ANR
headset would go away. I installed the mounting bracket of my GPS to have a
good point to run the antenna cable clear of the controls Here's a photo of the
setup:

http://www.bowersflybaby.com/tech/hhinstall.JPG

When I had it set up, I hit the temporary PTT for a test transmission into the
desktop radio.

A huge squeal filled the hangar.

Hmmmm...it appeared that the ICOM had MUCH higher output power than my Narco. I
couldn't even do a test transmission in the hangar, the desktop radio just
howled.

So...roll the plane out, hit the red button on the tape recorder, and off around
the pattern again, trying to remember to hit the doorbell temporary PTT instead
of the stick-mounted one.

As I rolled past Athol after landing, he gave me a big thumbs-up. The ANR
system had worked fine, too, not causing any interference.

So it appears pretty definite: My Escort II is toast. I'd still prefer a
panel-mounted radio. Narco *does* still say that they repair Escort II. But
I've been through the repair route once already. It's an old radio, though, and
is probably not worth another $300-$400 to band-aid it together for another
several years.

I've been taking a real close look at my ICOM IC-A5. I *think* I can do a
panel-mounted install in my avionics box, replacing the Narco. I'll have to cut
the top of the box away a bit to clear the antenna connector and other stuff on
the top of the radio, but that should't be too much of a problem.

I've already bought a "battery eliminator" that'll let me power the radio
exclusively from the aircraft power bus (thus I won't have to worry about
running down the radio battery if I leave it on). I think the battery
eliminator will have some space for me to put a mounting bolt through it...
gonna try some work with the poor man's X-Ray machine (drill press with a tiny
drill bit) to see if there's some clear real estate. If I plan the installation
right, I'll even be able to quickly remove the radio itself from the panel, and
still be able to handcarry it at fly-ins, etc.

It should be noted that I have not COMPLETELY ruled out the possibility that the
Narco isn't to blame. For instance, I haven't used the plane's built-in mike
jack to hook to the ICOM. If there's something wrong with that circuit, it
could be killing most of the audio to the radio itself.

I think it's unlikely, though. The feedback from the ICOM to the desktop radio
happens without actually saying anything over the mike. But I am going to hedge
my bets: I'm planning on installing the ICOM using Jim Weir's KARMIC (Kitplanes
Aircraft Radio InterMediate Connector) method... a generic connector in the
airplane allowing the quick swap of radios:

http://www.rst-engr.com/rst/articles/karmic1.pdf

I'll have to make a slight modification to accommodate the different way the
ICOM PTT system works. But with a standardized connector, I'll be able to swap
radios back and forth quickly. A Ham buddy has offered to do a little bench
testing of the Narco.

Bit too busy with writing projects to work on it right now, but hope to start
thrashing at it in a month or so. I'll keep folks posted....

Ron Wanttaja