On 1/8/2015 8:08 PM, Vigilant1 wrote:
Greetings,
I'm not a ham, but I am hoping a radio pro here can offer some advice.
I am a private pilot and the VHF radio in my plane (118-137 MHz) is not
behaving well. Reportedly my transmissions are weak and only partially
intelligible. I sent the unit back to the factory a year ago, they
replaced some bad capacitors and adjusted the TX frequencies, but now
the problem is back.

I bought a handheld unit (Yaesu FTA-550) and am considering just using
that in flight--it is legal, and performance is supposed to be adequate
if used with an external antenna. But, my installed radio (a Val 760
model) is a little more powerful and it is a less "kludgy" fit in my
aircraft's cramped interior.

I'd like to do some testing to find out if my existing radio really has
a problem, or if I've got a problem with my cable or connectors to the
external antenna.
Ideally I'd like to be able to see field strength and look at the
spectrum of the TX. Is there an inexpensive meter for doing this? I've
seen some very impressive add-ons for Android devices or USB devices for
laptops that do analysis of various kinds, and was hoping something
already existed for at least VHF field strength measurement. I won't
use it often, so I don't want to spend a lot of money, but an avionics
shop will probably charge me $100 just for a one-time diagnosis--I'd
rather have the tools to do it myself.

Thanks in advance for any assistance, and accept my apologies if I've
used incorrect terminology, etc.

Mark


Mark,

I am also a pilot. There is very little you can do legally with your
radio. The FAA regulates anything to do with the avionics pretty
closely. Even with a General Radiotelephone license (grandfathered from
a First Class Radiotelephone), I can't work on avionics legally
(although many years ago you had to have at least a Second Class to work
on most transmitters). And if you don't have the technical background,
you're likely to do more harm than good.

For instance, field strength won't do you much good without controlled
conditions and a comparison. Even then, it will only tell you what you
already know - that your signal is weak. It won't fix the problem for you.

Since you mentioned no problems with receiving, chances are it is not
the antenna, and you can ignore Jim's advice (which would be illegal if
you followed it, anyway). I know it hurts - but your best bet is to
cough up the Benjamin and have an avionics shop check it out. They know
what they're doing and can fix it for you.

And I would consider $100 cheap - it costs me more than that to rent a
Cessna 172 for an hour...

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Jerry, AI0K

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