Please help a newbie with noise problems.

[Justin H]

I have an open cockpit biplane and I'm using a garmin 190 for radio and GPS.
Its not connected to the airplanes systems in any way but it gets alot of
interference, maybe from the mags or something, while transmitting in
flight, recieving is not bad, and transmitting on the ground is ok.

Thanks for any help.

[Ron Wanttaja]

On Sun, 19 Sep 2004 20:19:59 -0400, "Justin H" > wrote:

>I have an open cockpit biplane and I'm using a garmin 190 for radio and GPS.
>Its not connected to the airplanes systems in any way but it gets alot of
>interference, maybe from the mags or something, while transmitting in
>flight, recieving is not bad, and transmitting on the ground is ok.

1. Do you have a wind muff on the microphone?

2. Some details of the electronic environment would probably help... do
you have a transponder, what mags are on the engine, are the mags and plugs
shielded, etc.

3. What kind of "interference" are you experiencing? What does it sound
like...audio distorted, regular bursts of noise, audio squeals, etc.

Ron Wanttaja

[Justin H]

The airplane does not have an electrical system so there arent any
transponders etc.. the mags are bendix s4ln. the mic has a muff but its not
getting any impulse air anyway (doesnt seem to be anyway) .

the sound reminds me of a car stereo system getting alternator whine, but
amplified. going to try varying the power and talking today.



"Ron Wanttaja" > wrote in message
...
> On Sun, 19 Sep 2004 20:19:59 -0400, "Justin H" > wrote:
>
>>I have an open cockpit biplane and I'm using a garmin 190 for radio and
>>GPS.
>>Its not connected to the airplanes systems in any way but it gets alot of
>>interference, maybe from the mags or something, while transmitting in
>>flight, recieving is not bad, and transmitting on the ground is ok.
>
> 1. Do you have a wind muff on the microphone?
>
> 2. Some details of the electronic environment would probably help... do
> you have a transponder, what mags are on the engine, are the mags and
> plugs
> shielded, etc.
>
> 3. What kind of "interference" are you experiencing? What does it sound
> like...audio distorted, regular bursts of noise, audio squeals, etc.
>
> Ron Wanttaja

[Ron Wanttaja]

On Mon, 20 Sep 2004 08:59:21 -0400, "Justin H" > wrote:

>The airplane does not have an electrical system so there arent any
>transponders etc.. the mags are bendix s4ln. the mic has a muff but its not
>getting any impulse air anyway (doesnt seem to be anyway) .
>
>the sound reminds me of a car stereo system getting alternator whine, but
>amplified. going to try varying the power and talking today.

Another thing you might try is switching one mag off when transmitting. I
have a high noise level on receive; fiddling with the mag switch, I found
the noise was a lot less when I turned off the right mag. I bought a
replacement noise filter capacitor, but haven't gotten around to installing
it.

If killing one mag eliminates the noise, then you've at least narrowed down
the source of the problem. Looking online, it appears the Bendix SC series
does not have an external noise capacitor, so it sounds like a repair would
be a bit more complex.

If the problem doesn't appear to lie in the mags, you might try a different
headset and headset adaptor. Also, are you using the "rubber duckie"
antenna or do you have an external antenna?

Ron Wanttaja