Avionics help

Hi guys,

So while on my way up to Portland my COM 1 went garbelled according to ATC...Its an ICOM A200 fed thru the audio panel.

There is a bent whip antenna on the belly...Reception is perfect...My Wife said she could hear weired sounds in her headset when I TX but the intercom works normally when not transmitting.

COM 2 was "Much better" (GNS430) although because I have a wingtip antenna is subject to sheilding.

My first thought was to swap antennas on the back of the units and see where the problem goes.

But then i thought I might ask if someone has a better approach.

Radios have been working normally up to now...But sometimes will get ignition noise passed thru...Then I usually change the (auto)plugs and it goes away...But I can normally hear it when this happens...Although for $9 I might just change the plugs anyway.

Thanks

Frank

Is it garbled when the other mic transmits, i.e. the copilot jack?

Garbled Transmit

Swapping antennas would be a good first step in isolating the problem.

An antenna with High VSWR (Voltage Standing Wave Ratio) could result in Transmit degradation but not adversely effect the receive function.

A watt meter would be required to confirm the ratio.

In my experience on the bench it sounds like a shorted modulator transistor in the icom. I have no experience w/ the icom but most 28 volt comms seem to get this problem. I would have a shop give it a quick bench test to confirm the problem. I have found bad ants and coax's usually give you very low range rx and tx. Let us know what you find
Jay
pilot2512

Frank

I know this might not be the problem but........all the upside down...sideways...over the top....figure eigths.......hammer heads have put great stress on all you electrical/antenna wiring.

Sorry couldn't resist!!!!!!!!!!!!!1

Frank2....RV7A still wiring ....starting the antenna stuff tomorrow

This is true....

fstringham7a said:

Frank

I know this might not be the problem but........all the upside down...sideways...over the top....figure eigths.......hammer heads have put great stress on all you electrical/antenna wiring.

Sorry couldn't resist!!!!!!!!!!!!!1

Click to expand...

The electrons may have started spinning backwords.

Kent

SWR

It doesn't sound like an antenna problem to me. Hi SWR will lower your effective radiated power and will burn up your RF power transistors depending on how high it is and how long you transmit. Many newer radios have a high SWR protection circuit to drop power levels down if it is detected. It shouldn't garble your radio transmissions though. I'd think what pilot2512 said would be more likely or something in the audio panel maybe. Might check power to the unit as well. If there is a bad electrical connection or the voltage at the unit is dropping too much it can make these little radios do funny things as well. This last thing may only show up while transmitting.

-Brian