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lrsecaldwell(at)earthlink
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 Posted: Sun Feb 28, 2010 4:54 pm Post subject: Noise in Handheld Tx signal. |
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We have a problem with excessive noise occurring in an ICOM A24.
Receive is good. The noise only occurs in the transmitted signal while
the engine is running, The noise is so bad the the voice is not
understandable. If the operator is about 100 ft from the A/B with the
engine running the noise is down to a level that is acceptable.
Th hsndheld is completely independent of the a/c. Internal batteries
and operation on the rubber duckie antenna. A headset is used. Two
different A24's with different headsets exhibit the same problem.
There are no avionics in the plane except for the handheld. To
eliminate the possibility of interference from instruments or alternator
we tested with the master off and the problem still exists.
Previously the A24 was used acceptably with an open cockpit biplane, a
Murphy Renegade.
One possibility could be excessive gain using the external mike, but I
am skeptical since it was acceptable in the biplane
Any suggestions?
Roger
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nuckolls.bob(at)aeroelect
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| Posted: Mon Mar 01, 2010 4:54 pm Post subject: Noise in Handheld Tx signal. |
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At 06:51 PM 2/28/2010, you wrote:
| Quote: |
Caldwell" <lrsecaldwell(at)earthlink.net>
We have a problem with excessive noise occurring in an ICOM A24.
Receive is good. The noise only occurs in the transmitted signal
while the engine is running, The noise is so bad the the voice is
not understandable. If the operator is about 100 ft from the A/B
with the engine running the noise is down to a level that is acceptable.
|
| Quote: | Th hsndheld is completely independent of the a/c. Internal
batteries and operation on the rubber duckie antenna. A headset is
used. Two different A24's with different headsets exhibit the same problem.
There are no avionics in the plane except for the handheld. To
eliminate the possibility of interference from instruments or
alternator we tested with the master off and the problem still exists.
|
Then it's not electrical noise. Sounds more like acoustic
noise coming in through the microphone(s).
| Quote: | Previously the A24 was used acceptably with an open cockpit biplane,
a Murphy Renegade.
One possibility could be excessive gain using the external mike, but
I am skeptical since it was acceptable in the biplane
Any suggestions?
|
You need to identify the nature of the noise. Props sound
different that exhausts which sound different than
ignition, strobes, EL panel inverters, etc.
If you key the hand-held with the external headset
disconnected and a tape over the built in microphone,
is it quiet then?
Bob . . .
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