tkatc

tkatc

Well Known Member
I have been getting reports from ATC that my icom A200 radios sound terrible. I've heard garbled, sctratchy, engine noise, etc. I can hear them fine. I originally was flying with Halo's and tried to resolve the issue with a pair of Bose Xs. The problem persisted so I figured it was not a headset issue. I have heard it could be poor antenna coax connections but my local radio shop said unlikely so I have not yet investigated that. I got a pair of Clarity Alofts and it was a MARKED improvement. Not perfect but much better. ATC still complains but i dont have to repeat myself now.

So now i figure that the Halo's mic is too sensitive or perhaps my mic gain is set too high. I flew yesterday and turned the mic gain all the way down. This doesnt work because i wont even tx at that level:). So i turned up the mic gain about a half a turn or so and that seemed to bring me back to intelligable tx but still scratchy. Anyone have any insight? What should my mic gain be set at? If it is too low will it not tx over greater distances?:confused:
 
Not sure what that means exactly Gil. The jacks are tucked up under the panel and are wide open at the rear with wire connections open and visible.
 
There should be brown or orange fiber washers around the mick jack to insulate it from whatever it is attached to. There will one with a flange and one flat.

EDIT: You beat me to it. :)
 
I would assume it is isolated. The builder is a smart guy but I will still check when I have time.
 
You can do a quick test on the ground by unfastening all of the jacks from the panel (single nut on the front) and plugging in your headset with the jacks just "floating" in space.

If this help the voice quality, then the jacks should be insulated by the fibre washers mentioned above.
 
When wiring is correct, and you still have a problem then adjust the radio gain. Slide the radio out if the tray and look for 2 foil covered holes. Gain and side tone. Remove the foil and mark the start locations of each. Turn down mike gain for transmit clarity (no background noise). Then adjust side tone so you can hear yourself.

I tested mine with a handheld and a recorder. My gain on my headset also needed adjusting. But that was after the radio was at it's best.
 
Thanks everyone! After i check the jacks i will work on adjusting the mic gain again. I figure the lower the gain, the less cockpit noise will be trnsmitted. My concern is the gain will be so low that my range would be affected. Does mic gain affect radio range or is it strictly a microphone clarity/sensitivity adjustment?
 
"I figure the lower the gain, the less cockpit noise will be trnsmitted."

Yes except less of your voice will also be transmitted (not a good thing).

Mic gain should really be adjusted to so that you have 100% modulation of the AM carrier when speaking normally and this will affect range to some degree. Without a modulation meter this can be hard adjustment to estimate. If you lower the Mic gain to much you will transmit a carrier with no/low voice. Radios these days will prevent overmodulation so generally keeping the mic more sensitive is better than less sensitive.
 
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Ok. My mic jack seems to be "insulated". I knew the builder was smart!! :)
There are fibrous washers installed between the metal washers. Wondering where to go now....:confused:
 
Pull the antenna off, if there is a gasket get rid of it, remove the paint under the antenna, apply some stick alodine, re-install antenna.

If that doesn't work keep an eye on the classified for an SL40 :eek:
 
tkatc said:
Ok. My mic jack seems to be "insulated". I knew the builder was smart!! :)
There are fibrous washers installed between the metal washers. Wondering where to go now....:confused:
Click to expand...

It should be true for all of the jacks, not just the pilot mic jack...:^)
 
Check all grounding

This problem sounds all to familiar. Be sure you have a good ground on all components, especially the antenna.
Woodman
 
Woodman, i am not sure where to begin checking for grounds:confused:

Today i pulled up the floor to get to the antenna connector. Looked good with the naked eye. I also removed one antenna and used some scothbrite to ensure good contact with the airframe but it was nice shiny aluminum before I even touched it so I doubt I did anygood. I did notice that the body of the comant ci-122 sort of interfered with the flat metal inards of the antenna....I thought above removing some of the material to allow full contact but didnt want to screw up the antenna.

I need more homework assignments before I either take it to a radio shop or buy new radios. I am wondering if my intercom, garmin 340, could play a role in this issue. I aslo noticed my coax runs along with some other bundled wiring....is that a problem?
 
Mic gain

Don't give up on the mic gain too soon. It was hard for me to get mine right on my A200. It's a very sensitive adjustment.

If you change headsets you have to do it all over again:mad:

Later I added an SL40 and you can set it's mic gain without pulling the radio!

Mark
 
gasman said:
When wiring is correct, and you still have a problem then adjust the radio gain. Slide the radio out if the tray and look for 2 foil covered holes. Gain and side tone. Remove the foil and mark the start locations of each. Turn down mike gain for transmit clarity (no background noise). Then adjust side tone so you can hear yourself.

I tested mine with a handheld and a recorder. My gain on my headset also needed adjusting. But that was after the radio was at it's best.
Click to expand...

Tony, read this......... http://www.oregonaero.com/p5657-2001.html

I also added these to my headsets along with adjusting the mike gain in the radio and the Lightspeed headsets....................... My radio went from really bad, to clear as a bell on each end.

Get the Mic muffs!!! they work!
 
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