Alternator noise on Xmit only

MikeMl writes:

Short from microphone connector ground to chassis.

Bingo,

Proper installation of aircraft mic and headphone jacks requires the
use of insulating bushing where the threaded sleeve on the jack would
otherwise come in electrical contact with the airframe.

And those those who've not seen them, you need shoulder washers.



...[======| |======]
PANEL| |****PANEL
.......[==| |==]
...[======| |======]



The outer [here lower] washer is two-step; the inner part centers the
jack in the panel hole. Sometimes the inner [here upper] washer is flat,
sometimes it's the same as the lower. Both are usually made of phenolic
or such; but could be any insulator.

And note that if any mike jack wiggles loose/gets off-center, you can get
a short. It's an easy thing to inspect.

And if the jack is mounted on a plastic panel; you can skip the whole
issue. I don't know how many are.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

So running a grounding wire from the jack to the radio tray is not enough?

I installed a jack to run the audio from my 496 to the audio panel in the
radio stack and at first just used the instrument panel as ground. I did
get a significant amount of noise. Then I added a ground wire from the plug
to the radio tray and got rid of the extra sound effects.

--
Best Regards,
Mike

http://photoshow.comcast.net/mikenoel


"David Lesher" wrote in message
...
MikeMl writes:

Short from microphone connector ground to chassis.

Bingo,

Proper installation of aircraft mic and headphone jacks requires the
use of insulating bushing where the threaded sleeve on the jack would
otherwise come in electrical contact with the airframe.

And those those who've not seen them, you need shoulder washers.



..[======| |======]
PANEL| |****PANEL
......[==| |==]
..[======| |======]



The outer [here lower] washer is two-step; the inner part centers the
jack in the panel hole. Sometimes the inner [here upper] washer is flat,
sometimes it's the same as the lower. Both are usually made of phenolic
or such; but could be any insulator.

And note that if any mike jack wiggles loose/gets off-center, you can get
a short. It's an easy thing to inspect.

And if the jack is mounted on a plastic panel; you can skip the whole
issue. I don't know how many are.


--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

"Mike Noel" writes:

So running a grounding wire from the jack to the radio tray is not enough?


You want to isolate the jack from the panel ground.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

On Jul 1, 6:34*pm, David Lesher wrote:
"Mike Noel" writes:
So running a grounding wire from the jack to the radio tray is not enough?

You want to isolate the jack from the panel ground.

--
A host is a host from coast to
& no one will talk to a host that's close........[v].(301) 56-LINUX
Unless the host (that isn't close).........................pob 1433
is busy, hung or dead....................................20915-1433

He's right you know. Otherwise, small alternator induced voltage
drops in the airframe will show up in series
with the mic. You puny little wire won't change that picture.
Isolation washers are the answer!!

Should be on the phones too.

Bill Hale