Constant crackling noise in intercom

[randylsnarr]

Sorry if this has already been covered. I have the full Dynon suite. I am getting a crackling noise in the headphones when the intercom is quiet. This goes away if I turn off both SV displays.
Ideas?
Randy

 

[dynonsupport]

Randy:

This may be applicable to your situation: http://dynonavionics.com/docs/support_bulletin_030512.html

Sorry if this has already been covered. I have the full Dynon suite.  I am getting a crackling noise in the headphones when the intercom is quiet. This goes away if I turn off both SV displays.
Ideas?
Randy

 

[randylsnarr]

Thanks for the info. My displays were purchased March 2013, a year after this bulletin, I had someone ask me about the serial numbers a while back an if memory serves, I was well outside the sn range. As I understand the bulletin, i do have the audio out from SV connected to my intercom. Crackling is present with displays on and transponder on, goes away when displays are off. It also goes away when the transponder is changed to standby.

Do you still think I need to return the displays?

 

[dynonsupport]

Randy,
That sounds like the issue is the transponder, not the displays. The transponder goes off when you turn off the displays as well. So I don't think you need to do anything with your displays.

Composite airplanes will always have a bit more of an issue here since they shield the audio wires less from the antennas than metal airplanes do.

First thing, what kind of Coax did you use for your transponder? The install requires RG-400 or better. We've had reports of this before, and the issue was the use of RG-58, which "leaks" a lot more than RG-400.

It's also important to make sure the transponder antenna has a correct ground plane. What did you use in the Lancair?

 

[meyerflyer]

I have a Lancair 320 also with SV1000 and transponder.  I hear this on occasion if my head set cord lays in the wrong side of the baggage area.  If I hear it I move the cord over and it goes away.  Fiberglass and RF can be a tuff thing sometimes. Do you have a good headset? The shielding in the headset can possibly cause it. Maybe try a different one temporarily.
Dan

 

[randylsnarr]

I am moving my transponder antenna from the tail up closer to the radios to the right wing. I am also changing to RG400 coax.
I will post my results in a few days.
Randy Snarr
Lancair 235/320

 

[randylsnarr]

I moved the antenna to the wing away from everything and replaced the RG 58 w new RG400. The new wire run does not pass by the intercom or headset jacks now.
Unfortunately, I still hear the crackling in the headphones.
The crackling noise is still present even with the com and intercom off.
Goes away when the transponder is turned off.
Actually seems a little worse than before...

Ideas?

Randy Snarr
Lancair 235/320
N694RS

 

[vlittle]

My guess is that you are hearing this on the ground in a hangar. The SkyView transponder puts out a lot of power and the mode s-es is always pinging. This Uhf energy is picked up by headset cords and is demodulated by the semiconductor devices in some anr headsets. The test for this is to totally unplug your headset and see if can still hear the noise. The headset does not need to be powered.

In flight, there are no reflective surfaces surrounding the transponder antenna so you should not hear this noise if I am correct.

Vern

 

[randylsnarr]

Vern, I get the crackling in the air and on the growing whenever the transponder is on. It stops when in stand by mode.
Crackling is still present with the com and inter com off.
I will try it with the headset unplugged..
Thx!
Randy Snarr