On Mar 28, 5:26 am, Nathan Young wrote:
On Thu, 27 Mar 2008 15:27:52 -0700 (PDT), Lancair IV-P Flyer

wrote:
Would anyone have an idea about the cause of this?

Two ideas to check:

#1. Use a battery powered handheld radio to see if it breaks squelch
as well. This will tell you if the noise is RF based or coupled into
the DC power within the plane.

#2. Have you replaced the field circuit breaker? I don't know how it
would cause the squelch issue, but a bad breaker might contribute to
some of the odd electrical system issues you are experiencing.

I had a bad field breaker that worked about 99% of the time, but would
occasionally exhibit a resistance, which caused a voltage drop across
the breaker, which caused the voltage regulator to crank up the
voltage. After hitting turbulence, the breaker would jostle just
enough to lose the resistance, and then the over voltage regulator
would trip, and take the alternator off line. I went through 2
alternators, a VR, and an OVR before I decided to debug this problem
myself and eventually found the bad circuit breaker.

-Nathan

Nathan,

Thanks for the ideas. I will try the hand held radio test. I have
already replaced the field circuit breaker. There was no change in
the symptoms so I don't think that made a difference. I am wondering
if the breaking squelch is unrelated to voltage excursions and breaker
tripping events. Since I can usually get the squelch to break on the
ground, I am thinking of pulling breakers one at a time while the
squelch break event is in progress to see if there is an instrument
that may be causing that noise.

Thanks again,
Steve