lml@lancaironline.net Mailing List Archive

I had that problem once. It is caused by RF pick-up on the audio wires/cables/circuits and subsequent detection and amplification through the receiver. I solved the problem in my plane by installing some (3) ferrite toroids on each headset cable. The toroids serve to choke off the RF currents in the audio wires.

The head set cable has to be disconnected from the plug or some other point in order to slip on the toroids. I suggest you try left side only first.

I purchased the toroids from DIGI-KEY on-line. Part number 240-2067-ND.

Bob Jude

N65BJ - still looking for a buyer.

----- Original Message -----

From: Dominic V Crain

Sent: Wednesday, August 23, 2006 2:01 PM

Subject: VHF feedback

Any advice on this one.

Have a problem with loud squeal on VHF transmission – happens with both VHF sets, but only from the left side. Right side doesn’t happen.

Have done all the suggested things from onlookers, cleaning terminals, etc etc., and it only occurs after engine start.

Use Lightspeed ANR 20G headsets.

Changed the SPA 400 intercom with another identical unit – no avail.

Can’t quite recall when it started. Wondered if the installation of Infinity grips in March might have introduced it with a wiring problem – this was done by a avionics technician.

Switching off the intercom and it goes away.

It is quite loud.

Any final suggestions?

Dom Crain

VH-CZJ