Vigilant1 wrote:
;833309 Wrote:
An external instrument will tell you very little and the cheapest
inline instrument that would be useful (a SWR meter) is going to
cost at least $50 to buy, which is getting close to the $100 shop
fee without having done anything.
. . .
Jim Pennino
Jim,
Thanks. So, do what I can to improve the integrity of the most
obvious/easily fixed failure points external to the radio. An SWR can
be used to see if what I'm doing is improving things, at least as far as
the antenna, then it's just a check of the physical condition of that
piece. Seems simple enough.
A SWR meter will tell you about the integrity of the cable and antenna
as a system.
Of course the SWR won't tel me anything about the integrity of the
signal itself (am on on frequency, is it spilling over, am I
overmodulating, etc).
That will take a bunch of rather expensive equipment for a one off fix.
And if any of those things are bad, you will HAVE to send the radio
somewhere as there is nothing you can do about any of those things
without the maintenance manual, a pile of test equipment, and an
appropriate piece of paper from the FAA.
Can I learn anything by checking the cable's (cable and connector's)
resistance? It's 50 ohm cable and about 12 feet long.
Not much; if the resistance between the center conductor and shield is
less than infinity you have a short/grundge/corrosion problem.
Again, I appreciate your patience and support.
Mark
One other thing to look at if the problem is transmit audio; check the
mic/headset connector. It too should be clean and shiny.
Mandatory war story...
Back when I worked at the avionics shop, about twice a year some guy (not
the same guy every time) would come in with some piece of avionics in
a cardboard box that was partially disassembled.
My first question was "Engineer at General Dynamics?", which was nearby.
The guy would either nod or mumble yes and I would give him the paper
to fill out and tell him we would call when it was working.
The moral here is that for other than simple stuff, test equipment and
skill are not enough, you also need the manufacturers maintenance manual.
However, a large portion of flaky/intermittant issues were due to
loose/dirty/corroded connections, so start there.
And if you do find the antenna or cable to be toast, you will at least
save the labor of the tech discovering that.
--
Jim Pennino