Radio Noise

[GrassStripFlyBoy]

Have noticed radio (King KY97A) is not as clear when under cruise power compared to idle.  Condition is a scratchy static, not a whine or high frequency noise.  Not horrible, I'm getting by, but find it interesting that lower RPM settings when in pattern is crystal clear.  I've turned off some of the new items I've installed, EFIS, USB power source, and other electrical items such as transponder, and no difference.  Appears to be entirely engine power setting related.  Any thoughts on this?  I think it has always been this way since my ownership, and one of those things I've more recently noticed.

[GrassStripFlyBoy]

Solved the noise situation.  Assumed it was most likely the antenna ground as that is frequently the source of degraded radio signals.  The coax connector was clean and tight.  The 4X mounting screws, which provide electrical connection to ground plane plate were the issue.  Two were loose with zero clamp force developed to fasteners, spun easy.  The electrical connection path is antenna base countersink screw surfaces (composite with what appears to be conductive carbon filler), the 4X stainless screw heads contact the base, then the threads of screws to threads of lock nuts, then face of lock nut back to the ground plane plate.  Add up all those items and connection is relying on 6 individual surfaces to develop electrical path.

Hit the antenna screw holes with scotch bright, same with screw heads (spun in drill), threads, nuts, and ground plate.  Many items were dull and slight oxidation shown.  Coated with DC4 and tightened up.  Ohm meter pegs nearly no resistance in check, wish I had a before reading, would have been interesting to know what the connections were doing prior to clean up.

Test flight is crystal clear, even on the calls way off in distance.  This is an easy enough task to complete, if you're flying older SW's like mine, might want to put this on your PM to do list.

[Animosity2k]

14 hours ago, GrassStripFlyBoy said:

Solved the noise situation.  Assumed it was most likely the antenna ground as that is frequently the source of degraded radio signals.  The coax connector was clean and tight.  The 4X mounting screws, which provide electrical connection to ground plane plate were the issue.  Two were loose with zero clamp force developed to fasteners, spun easy.  The electrical connection path is antenna base countersink screw surfaces (composite with what appears to be conductive carbon filler), the 4X stainless screw heads contact the base, then the threads of screws to threads of lock nuts, then face of lock nut back to the ground plane plate.  Add up all those items and connection is relying on 6 individual surfaces to develop electrical path.

Hit the antenna screw holes with scotch bright, same with screw heads (spun in drill), threads, nuts, and ground plate.  Many items were dull and slight oxidation shown.  Coated with DC4 and tightened up.  Ohm meter pegs nearly no resistance in check, wish I had a before reading, would have been interesting to know what the connections were doing prior to clean up.

Test flight is crystal clear, even on the calls way off in distance.  This is an easy enough task to complete, if you're flying older SW's like mine, might want to put this on your PM to do list.

I have this same issue on a 2011 CTSLi, I've got a lot of static even on close calls. The only thing that ALWAYS seems to come in crystal clear for some reason is when I am on with Cleveland Approach Control. Any CTAF usually has quite a bit of static / fuzz when I push the PTT button in. Think this could be the same issue? Any photos of where these connections are made / how to access them so I can try it? 

Thanks!

[Andy A]

I'd like to see some pictures too.  

[GrassStripFlyBoy]

Not much to this, ripped a picture off the web.  Open your baggage door, there will be a metal plate with the antenna mounted on top with four screws / nuts.  Note the direction of plate, not that it is critical to function but FD does not drill the holes in a perfect square pattern, and orientation should be same to easily pilot the screws back in place.  The antenna coax removes from antenna with a twist lock connector, scotch bright up / clean everything on these 4 screws, buy new nuts if they are not clean, then reinstall.  DC4 is Dow product, can buy off ebay or other places, this is not required but may help preserve the job going forward.  Put attention on the antenna base mounting holes, and screw heads, as that is where water can collect and oxidize things.

If you have a couple long socket extensions that helps to reach both the nut on the inside, while holding a screw driver on outside.  Or get a second person to help you, I was just able to do this on my SW alone, a second hand would make it easier.  LS might be easier or harder reach - don't know.

To check the job, place multi meter to lowest Ohm setting, touch probe to outside of antenna connector and other to the metal plate.  Was reading .002~.003 when completed.  These are small screws, don't crank them crazy tight, just snug up as M4 would be good. 

[GrassStripFlyBoy]

2 hours ago, Animosity2k said:

I have this same issue on a 2011 CTSLi, I've got a lot of static even on close calls. The only thing that ALWAYS seems to come in crystal clear for some reason is when I am on with Cleveland Approach Control. Any CTAF usually has quite a bit of static / fuzz when I push the PTT button in. Think this could be the same issue? Any photos of where these connections are made / how to access them so I can try it? 

Thanks!

I too noticed difference with what freq / ATIS v/s ATC v/s other planes, so perhaps yes on that note.  As far as when you push PTT, I don't think so.  You should not be hearing "anything" incoming when you key the mic, so that could be an intercom or headset issue, I'd start by trying a different headset, then also try bypassing intercom with those back up com plugs, or shut of intercom and rely on just the radio for a cross check.  I'm far from an avionics expert, take my inputs here for what its worth...

My take on this is flying should be a joy, and safe.  If your radio is causing grief, take it to shop and get it fixed, don't live with it.

[Animosity2k]

1 hour ago, GrassStripFlyBoy said:

I too noticed difference with what freq / ATIS v/s ATC v/s other planes, so perhaps yes on that note.  As far as when you push PTT, I don't think so.  You should not be hearing "anything" incoming when you key the mic, so that could be an intercom or headset issue, I'd start by trying a different headset, then also try bypassing intercom with those back up com plugs, or shut of intercom and rely on just the radio for a cross check.  I'm far from an avionics expert, take my inputs here for what its worth...

My take on this is flying should be a joy, and safe.  If your radio is causing grief, take it to shop and get it fixed, don't live with it.

It's just a bit of static muffling the incoming conversation when I'm on the mic. Doesn't make it impossible to hear, however can't adjust the squelch to get rid of it.