K

Kye Wehrell

I'm New Here
I have just completed my RV-6A and have 11 hours TT. It has definately been a blast to fly and worth every bit of the 13 years I spent building it. My question to you all is this. I have an Icom - A200 radio with a bent whip antenna on the underside of the fuselage at the baggage compartment area. When I start up the plane and make my radio call while the engine is idling the transmission is perfect no background noise at all, while taxing to the active perfectly clear transmission, once I get airborne and I am zinging along at 180 mph and I hit my PTT on my stick I hear a loud static sound that is similar to as if I stuck my headset mic outside the cockpit and it was in the air blast. The sound is not like an alternator whining sound, but more similar to someone blowing directly into the mic. The tower and other planes can hear my transmissions fine, however with all this additional - what sounds like cockpit noise also entering the mic. As I reduce power on my descent to land the background noise while transmitting reduces proportionally to the RPM reduction. If I didn't know any better I would think it was simply cockpit, air, vibration noise being picked up by the mic. I have tried 3 other headsets and they all do the same thing? I hope someone out there has experienced this same issue and may know of solution or some guidance for me. Thanks in advance.

Kye
 
I'm sure you checked but.....are you sure your fresh air vent isn't blowing into mic? I've experienced the same thing.....right up until the fresh air vent was repositioned away from the mic.
 
Hey Kye!!

Can you tell if the ICOM has a mic gain adjust? If so you may want to try that because I had to turn mine way down on my SL-30. I tried looking in the ICOM manual but couldnt find anything about it... it may be a pot on the box itself you have to adjust externally. There are lots of users of this radio on this board so I'm sure you'll get an answer.

http://www.icomamerica.com/support/manuals/ic-a200.pdf

11 hrs? Go fly those hours off so we can go places.

You can try one of my headsets if you like.

Best,
 
I had a heck of a time with radio noise (in another airplane) until I ran a seperate ground wire from the negative post on the battery to the radio. Worth a try if adjusting the gain doesn't help.
 
Mic gain and sidetone

This is a common problem with the A200. I had the same experience. The factory settings for Mic gain and sidetone are set way too high for our noisy RVs. You'll need to remove the unit from the rack, and peel off the little silver stickers, but you'll see the two adjustment pots on top of the radio. It takes a little trial and error but adjusting them is the solution. It can be done in flight, but it's a little tricky to adjust the pots in any turbulence.

Remember- adjust the mic gain so the world can hear you, then adjust the side tone so you can hear yourself properly. Do it in that order.
 
Mike impedance and voltage bias

Also make sure your headset's mike impedance and bias voltage thereto are compatible with the A200 or the intercom box, before making radio adjustments. Make sure the mike is wired correctly, from mike to box, including male/female plugs. Pay particular attention to grounds, including shields. Also, most RV's really need a noise cancelling mike. If you've done/have done all this, pls disregard. Good luck.
 
icom radio noise

this sounds to me like some kind of problem with the automatic squelch. i notice that on the install diagram, there is a pin called "squelch cancel" -- but no description of the usage. i'm wondering if maybe some stray rf is triggering the squelch cancel function. assuming it is a "logic" input, perhaps a 10k ohm resistor tied either high or low (don't know which because of the lack of description in the install manual, but i would guess tie it high) might prevent noise from triggering this function.

again, i don't know for sure, but this would be one experiment that i would think would be worth trying.
 
Could happen

What kind of mic. You try a foam mike spit/wind/pop cover. The other suggestions all sound better than mine but is your mic turned the out? Good mics are very directional but sound can enter in both directions. That is to counter background noise.
 
Mic gain

Just had the same problem with my XCOM 760. I dropped the mic gain (thankfully it is software adjustable) and I am getting "loud and clear" on radio checks now. I had tried several headsets; same noise.

Bob Kelly
 
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