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Dave S
10-27-2008, 06:34 PM
I Have encountered a situation with my radio/intercom/headsets which I still haven't figured out. I am wondering if any of you have any ideas on where to start on this one. Honestly, avionics I consider somewhat of a black art since I haven't had a lot of training. I can read wiring diagrams just fine - but I still can't see electrons too well.

Here is what happens; and I don't know if the radio, the intercom or the headset is to blame. There is a noise, similar to a squelch noise which is in the background only when transmitting and only when flying at moderate or better power settings. Receiving is just fine - always. Impressions can be deceiving, but the background noise seems to have something to do with the background noise in the cockpit - in other words - it is only there if there is a lot of noise in the cockpit. It does not seem to be RFI from the ignition nor from the strobes - I am real familiar with that from rental planes.

The radio is an Icom IC A200, the Intersom is a softcom panel mount and the headsets are older Softcom units which I have used in a lot of other aircraft (they are not the high tech noise reduction ones - they are the plain Jane ones).

I have replaced the headset phone plugs and cleaned up the jacks (jacks are new - but had some crud on them), checked the grounds and shielding - that seems to be OK.

Any Ideas are truly appreciated.

Didn't get a lot of flying this weekend - snow was horizontal and the birds were walking.....

Sincerely,

Dave S
St Paul, MN
Kitfox 7 Trigear

RandyL
10-27-2008, 06:58 PM
Many com radios have adjustable mic gain. Check the manual and see, worth a try. Alternatively, borrow a couple other brands of headsets to see if the problem persists.

SaintAero
10-31-2008, 08:09 PM
Dave, This is a common problem in plastic airplanes. I built a Glasair and found that triax cable is a good solution to prevent RF interference (at the source). I had several problems using coax cable for the antenna where others have a quiet system using triax. Eg., my stereo intercomm muted the music every time the transponder replied. I also had garbled sidetone when transmitting, but it was clear to other aircraft. Separating the mic and headphone wires from the transmitters is a solution, but not as reliable. Let us know when you solve this one. -- Don

jdmcbean
11-04-2008, 02:04 PM
Dave,
Sounds like the it may be the side tone or mic gain... Also, check the wing root area of the wing.. Are the fairings installed ? If not plug the holes with some foam.. there is a lot of ambient noise that comes in through the wing root area without the fairings installed.

Dave S
11-07-2008, 05:39 PM
Guys,

Thanks for the ideas - I am taking a long weekend and going to try to get this solved. I'll let you know how it works out.

Dave

Dave S
05-18-2014, 04:53 PM
All,

I realized I promised to get back to everyone way back in November 2008 as to what I found out on this issue you folks provided advice on; but, it appears I didn't carry through......:eek:

Anyway, what I found out is the background noise on transmitt was due to the mic gain not being correctly set...I had adjusted it a bit without success...I wrestled with it a bit because I wasn't real sure how far a person could spin that little screw driven pot in the radio...seemed to take a lot of backing off on the screw. I had no idea how far was too far or what the limits were on now much adjustment a person could do without breaking something...I guess the thought of busting a new radio kept me from going as far as necessary on the adjustmentm at first.

I also searced a little and found an explanation on another list where the opinion was that ICOM radios seem to come from the factory with the mic gain set WAYYYYYYYYY.... high.

Anyway, with a more radical adjustment on the mic gain, the radio worked fine.....even cranked up the side tone a bit to balance that and all is well.

So it appears that ICOM radios are a bit off from the factory on this setting and all that it needs is a lot more cranking on the fragile looking little pot for the mic gain.

Oh....and the panel mount intercom works fine with it to - I did not wire radio to use the radio intercom which I understand has some limits.

Sincerely,

Dave S
KF 7 Trigear
912ULS Warp Drive

Peteohms
05-28-2014, 06:04 AM
Last year I went to Mud n Fun. While there I bought a dual cigarette lighter/USB adapter to charge my iPad in flight. While flying, I plugged it in with my iPad and I got radio noise. Unplug, no noise.

Dave S
05-28-2014, 03:49 PM
Pete,

That is interesting.....I don't use an Ipad in the cockpit; however, I have a dual cig lighter tap that Is used to power the GPS....

Got any idea if your noise issue was related to the Ipad or to the power tap?

Thanks,

Dave S
KF7 Trigera 912ULS
Warp Drive
St Paul MN

Peteohms
05-28-2014, 04:40 PM
Dave, It was a defective power tap. Got a new one and everything is fine. I used to tinker with electronics. Once built a power supply that put out a bunch of radio and tv interference. Turned out to be a bad voltage regulator IC.