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Re: COM static
Posted: Sat Jul 30, 2022 1:49 pm
by Steve
Boatguy wrote: ↑Sat Jul 30, 2022 5:11 am
Yesterday we tested the static wicks and they were all within spec.
Later, the guys across the alley from my hangar, who restore legacy aircraft (they were wheeling out a T6 and expecting a P-51) said it was a ground issue. This kind of resonated with me. The static is not when I'm Rx/Tx, only when idle. Mostly when on the ground, but sometimes in the air and when monitoring Guard.
Is there a ground on the antenna or something that could have been disturbed in the annual?
I'm reluctant to tear the plane apart and break something else while trying to fix this.
Yes, aside from the antenna ground plane, there are bonding straps and shielding braids, in addition to the coax cable shield. See photo below of my dorsal COM/GPS antenna from the inside of the fuselage:
- COM/GPS internal
I know that a bad ground plane will cause decreased radiation of the transmitted signal and reduced receive range, not sure about static. When I installed this antenna as part of the ADS-B OUT install in my airplane, I noticed that some of the ground connections to the old COM antenna were corroded - spent some time with an air grinder and Scotchbrite cleaning them up. Yours could be in a similar condition...
Re: COM static
Posted: Sat Jul 30, 2022 3:08 pm
by Rich
I don't know if the G1000 com modules have this but for the GNS units there is a procedure for setting the auto-squelch. It is done for three different points on the com range and the unit interpolates from there.
Perhaps there is a similar procedure for the G1000?
You might also try looking at the transmitting side. While this is going on on the ground, try turning off certain things and see if what's causing it is leaking signals from your plane.
Re: COM static
Posted: Sat Jul 30, 2022 4:36 pm
by haykinson
I had a similar situation once when I had tried to save money and bought very cheap ($100) headsets off Amazon for my passengers. The microphone was overly sensitive or something similar, and was just always on, so I constantly heard static. I kept trying to mess with squelch etc and nothing helped. So I bought a second headset, thinking the first one was just bad, and the problem repeated. The most basic noise in the airplane would engage the mic and I’d hear static. So eventually I gave up and bought Lightspeed Sierras and never had this issue again.
So, if you haven’t already, try another headset. Maybe something degraded in yours and it’s just always on, engaging the intercom, in which case no amount of troubleshooting the airplane would fix things.
Re: COM static
Posted: Sat Jul 30, 2022 6:02 pm
by Boatguy
haykinson wrote: ↑Sat Jul 30, 2022 4:36 pm
I had a similar situation once when I had tried to save money and bought very cheap ($100) headsets off Amazon for my passengers. The microphone was overly sensitive or something similar, and was just always on, so I constantly heard static. I kept trying to mess with squelch etc and nothing helped. So I bought a second headset, thinking the first one was just bad, and the problem repeated. The most basic noise in the airplane would engage the mic and I’d hear static. So eventually I gave up and bought Lightspeed Sierras and never had this issue again.
So, if you haven’t already, try another headset. Maybe something degraded in yours and it’s just always on, engaging the intercom, in which case no amount of troubleshooting the airplane would fix things.
Thanks, but my problem is triggering Rx, not Tx. I use a Lightspeed Zulu which has never been a problem. This static problem is only when there is NO traffic (Tx or Rx) on the radio. I hear other transmissions just fine and ATC always reports my radio as "loud and clear". The problem appeared after the last annual so I'm pretty sure something was disturbed in the annual. Seems like maybe a bad ground somewhere in the antenna leads.
I guess I'll start by removing the headliner and seeing if the dorsal antenna wiring looks good.
Re: COM static
Posted: Fri Oct 07, 2022 5:02 am
by swillson
Thanks, but my problem is triggering Rx, not Tx. I use a Lightspeed Zulu which has never been a problem. This static problem is only when there is NO traffic (Tx or Rx) on the radio. I hear other transmissions just fine and ATC always reports my radio as "loud and clear". The problem appeared after the last annual so I'm pretty sure something was disturbed in the annual. Seems like maybe a bad ground somewhere in the antenna leads.
I guess I'll start by removing the headliner and seeing if the dorsal antenna wiring looks good.
did you ever get to the bottom of this?
Re: COM static
Posted: Fri Oct 07, 2022 6:12 pm
by Boatguy
swillson wrote: ↑Fri Oct 07, 2022 5:02 am
Thanks, but my problem is triggering Rx, not Tx. I use a Lightspeed Zulu which has never been a problem. This static problem is only when there is NO traffic (Tx or Rx) on the radio. I hear other transmissions just fine and ATC always reports my radio as "loud and clear". The problem appeared after the last annual so I'm pretty sure something was disturbed in the annual. Seems like maybe a bad ground somewhere in the antenna leads.
I guess I'll start by removing the headliner and seeing if the dorsal antenna wiring looks good.
did you ever get to the bottom of this?
No, though the problem has diminished significantly. I still get static at startup, and from time to time at some locations at some airports, but for the most part it's dropped down on my list of annoying things.
Re: COM static
Posted: Sat Oct 08, 2022 12:19 am
by haykinson
I just started getting this problem. A quick spray of contact cleaner seems to have reduced the static quite a bit. My symptoms were pretty strong static, which reacted to me playing with the plugs.
Re: COM static
Posted: Sat Oct 08, 2022 1:47 am
by Steve
haykinson wrote: ↑Sat Oct 08, 2022 12:19 am
I just started getting this problem. A quick spray of contact cleaner seems to have reduced the static quite a bit. My symptoms were pretty strong static, which reacted to me playing with the plugs.
I think that oxidation of the plugs can be a cause of this (it happened to me a couple of times). Now, I do preventive maintenance when my headsets are home, out of the airplane during the Annual Inspection. A few minutes of Scotchbrite pad action makes them nice and shiny (and quiet).
You can also clean the jacks using a brass .30 caliber bore brush.
Re: COM static
Posted: Sat Oct 08, 2022 5:28 pm
by Boatguy
haykinson wrote: ↑Sat Oct 08, 2022 12:19 am
I just started getting this problem. A quick spray of contact cleaner seems to have reduced the static quite a bit. My symptoms were pretty strong static, which reacted to me playing with the plugs.
When you have static it is breaking the Rx squelch? You're seeing the Rx light on the radio?
Re: COM static
Posted: Sat Oct 08, 2022 6:05 pm
by haykinson
The static was not radio noise but more like electrical contact noise. I did not check if it’s causing RX to light up. Both pilot and copilot could hear it, however. It did not go away when unplugging the pilot side microphone, but it got worse when wiggling the pilot side headphones plug. Sprayed contact cleaner in all of those, wiggled the plugs a bunch, and it seemed to have gotten way better (at least one flight in).