RF interference issue again (esp. for E Drucker and Jim Weir and other RF wizards)

On Wed, 05 Nov 2003 11:10:29 -0800, Jim Weir wrote:


I think we are chasing our tails here, folks. Snowbird says that she gets the
interference on her handheld. Let's do the binary troubleshooting tree.

Split the problem into two parts. It is either IN the aircraft or OUT of the
aircraft that the problem is located.

Depending on how often this problem occurs (once a week? once a day? once an
hour?...) DRIVE the handheld out near the antenna farm and sit there and listen
on one of the most affected frequencies.

As a suggestion, try a bigger antenna on the HT if it has the
connector.


Does it still happen? Then with 99% probability, you've got a problem not of
your own making.

HTs are notorious for running the front ends wide open so it could be
the HT. Although out of all the HTs I've owned including commercial
(Motorola), I've only had one that was bad on intermod. Given a
strong enough signal any of them would intermod, or rather cross mod,
but virtually any radio will do that.

OTOH, I've had two out of 7 mobile rigs that had a problem. Course
when all is totaled up I've run into as many commercial installations
in the area that were either intermoding with each other, or
transmitting spurs. (which ain't many after this many years)

My biggest problem is a paging system about two miles from me that has
a problem about once a year.


Does it not happen? Then you've got a problem in the aircraft.

Let's settle THAT one and we can go from there.

Or, rather than drive out and sit for hours in the wintertime, do you have any
friends that live near the farm? Would they be willing to sit your handheld in
their window and listen for a few days?

If possible stick an antenna out the window of a nearby home and then
set one of those voice activated tape recorders next to it. Come back
about the time you expect the batteries to go dead. It makes for a
good check and doesn't require constant attention.


All else at this point is conjecture.

They are bad enough to find even using a systematic approach. :-))

Roger Halstead (K8RI EN73 & ARRL Life Member)
www.rogerhalstead.com
N833R World's oldest Debonair? (S# CD-2)


Jim
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com