My interpretation of that is that the actual intercom connector pin (or
a wire connected to it) for the internal radio intercom in that
particular model radio was picking up noise like an antenna and that the
pin was physcally removed to fix the problem. I would not worry about
something that unusual unless you happen to have the same model radio.
In my experience noise from a ground loop can indeed vary in pitch with
RPM so a ground loop could be involved. Current best practice seems to
be to join all intercom and radio grounds together and then run one wire
from that to the main ground for everything else. Operating the radio
from a separate battery that does nothing else should prove whether the
noise is coming from the DC supply.
I've noticed that when antenna's are involved the issue is often a coax
connector or a bad ground at the antenna.
Ken
Mike Kimball wrote:
Thanks Ken. I should spend some time on Aeroelectric. I'm on my third set
of auto plugs with no change (experimenting with heat range). Eliminated
the alternator by running the engine without the alternator (took the belts
off and left the alternator master off). The intercom thing sounds
interesting. Sounds like just having the intercom turned off was not enough
to eliminate it as a source for that guy. I wonder if pulling the intercom
out of the tray is enough to eliminate it as a source. Getting to an
"intercom pin" (what in the world is that?) on the back of the radio is
pretty much impossible.
Charlie - thanks for the GPS suggestion. No GPS installed right now. I'm
set up for my handheld but have not put it in yet.
Someone suggested disconnecting the radio gound wire because the radio may
be grounded through the mounting tray and the two grounds might be causing a
loop. I'd like to try that although I've been told that if the noise
changes in pitch with RPM it is ignition related and probably not grounding.
Again, thanks everyone and keep the suggestions coming. I'll put together a
list so I can work my way through when it warms up enough to do that.
Mike
-----Original Message-----
From: mike.davis@dcsol.com [mailto:mike.davis@dcsol.com] On Behalf Of Ken
Sent: Saturday, November 24, 2007 5:09 AM
To: rebel-builders@dcsol.com
Subject: [rebel-builders] Radio noise
Mike
Here's a couple more ideas from aeroelectric if you are not on that list:
Ken
Has it always been there or did it come about after a few hours running?
Sometimes I get ignition noise...Then I change out the auto plugs and it
goes away.
If you have auto plugs on your EI it might be worth a try for a $1.20 a
piece...then turn off your mag in flight.
frank
Have you considered the alternator regulator starting to regulate at 2000
rpm upwards, and the more pronounced effect this could be having with an
older battery, letting transient noise into the DC bus?
Ralph
I had an exactly identical problem with a KX155. There was a thread on it
several months ago
Eventually found it was the intercom picking up ignition noise. To diagnose
it i had to remove the intercom pin from the back of the radio. Most, but
not all, of the noise disappeared. Just working on one headset without
removing the intercom pin-out still gave the problem. Solved it by
installing an external intercom.
- Frank
Mike Kimball wrote:
buggingI haven't finished trying all the suggestions that came from the list on my
radio noise. The answer might be there! If it isn't I'll just keep
the list until it is! Thanks list!
Mike
044SR
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