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

A couple of items I forgot to mention...

If your antenna is the metal rod type, there is no connector as such,
just a couple of terminals attached to the end of the coax with the
center conductor under a nut on the end of the antenna rod and the
shield connected to the airframe with a screw.

Check that the hardware and connections are all shiny and tight. The
hardware should be stainless steel. If not shiny, clean with something
like a Scotch-Brite pad. Do not use steel wool.

BTW, if things need more than cleaning you will need to either have
someone who is FAA approved do it or inspect and sign off on your work
to be legal.

Also replacing the coax will require tools you will likely not have.

It is a good idea to establish rapport with your local tech's so they
will sign off on your work. And if they really like you will allow
you to use their tools. Owner assisted annuals is a good way to
start and will save money.

Here's a couple of articles about what you can legally do on your
airplane:

http://avstop.com/technical/maintenance/maintenance.htm

http://www.flyingmag.com/aircraft/mo...-you-can-do-it





--
Jim Pennino