radio problems

My Icom A200 usually works well

However when I select 128.00 the frequency of Tyabb, one of my local airfields, I get an intermittent noise

that sounds as if someone on the channel has an open mike.

When I transmit this noise will continue for several seconds after I conclude my transmission and if

I flip to another frequency the noise stops but is still there if I flip back to 128.00.

Over the top of this noise I can communicate OK with other aircraft.

When selecting 128.05 or 127.05 there is no problem

When well out of range of any station on 128.0 i still hear what sounds like someone on channel intermittently

transmitting.

I don't have any trouble on any other frequency that I have tried.

any and all advice greatly appreciated.

David

This is a "long shot" suggestion, but do you use an iPad charger in flight?

I had a similar issue that was resolved when I got a higher quality USB iPad charger from Jaycar. Apparently, the cheap ones can generate all sorts of unpredictable RF hash, sometimes affecting specific frequencies.

Worth trying, anyway...

or a GPS running

Simply increase the squelch setting a little and see what happens. Your radios receiver may be 'at its best' on this frequency.

Friend had similar problem in his warbird. Too much time spent on the one freq and the remote head for the radio - all the contacts had jiggled enough to become a bit dirty and unstable. A spray inside with electronic contact cleaner plus a bit of light cleaning on the dial contacts did wonders. Frequent changing of the frequency would have probably kept the contacts all nicely working. Not sure if you can get into the box to do that yourself. Hope this helps.

Suggest you try a portable receiver, a scanner or portable radio, see if it picks up the same interference. A harmonic from other equipment such a charger or GPS can cause such problems, sometimes (rare) instability in the radio. Could also be an 'image' - is there an FM station on 106.6MHz nearby? Google 'superhet image frequency' for an explanation. Best of luck! (and let us know what it is!)

Tried switching off all electrics apart from master and radio and while fiddling around noticed that the noise varied and sometimes stopped when I moved the power cord to the GPS which is mounted adjacent to the Icom.

I Unplugged the GPS power with no effect. ( It is powered from one of those cigarette lighter plugs) with no change

then I removed the GPS from its cradle also no effect.

Garmin Aera 500 and Icom 200

The cradle is mounted next to the radio and when I wave the unplugged power cord that is attached to the empty GPS cradle the noise varies with movement of the cord.

I am wondering is it the length of the cord is acting as a tuned antenna causing the problem, I don't particularly want to change the position of either the GPS or the radio.

Would a ferrite ring around the GPS power cord be likely to resolve the problem

many thanks

Davidh

Ferrite ring a very good start, but first - When you unplugged the GPS did you unplug its power supply or did you disconnect the power supply from the GPS leaving the power supply turned on? I suspect the latter, and moving the lead around will change the coupling to the radio. Put the ferrite next to the PSU, if it works, good, but it may be a good idea to find a better PSU. Unfortunately, radio interference is not high on the list of priorities for consumer electronic design, and even then it may 'pass the requirements' but be a pain when you have a sensitive receiver.