COM static

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Boatguy
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COM static

Post by Boatguy »

I'm getting lots of static on my radios when on the ground and a lower altitudes. It seems like the radios are super sensitive and have crazy static when nobody is talking, but I speculate that a very faint signal is being received. Sometimes the static triggers the Rx indication, but not enough to hear a voice. Sometimes just static and no Rx. It’s as though the squelch is set to some very low threshold, but I’m not aware of any way to set the squelch for the COM radios, other than ON/OFF.

It’s on both radios and seems to have started after the last annual, though of course nothing in the annual intentionally touched the avionics. The HIRF box was not opened and a subsequent exam of the antennas didn't show anything obvious.

ATC receives me 5x5 and I have no problem hearing transmissions from ATC or other aircraft.

In Thermal (KTRM) yesterday I had intermittent static on the CTAF (123.0). Then when I loaded guard (121.5) on the climb out there was a lot of static, but it went away as I climbed out. There are no issues at cruise (typically 8,000' - 13,000').

Approaching KSTS I had no issues with the tower (118.5), but back on the ground I was again getting intermittent static on the ground frequency (121.9).

There was an MSB which specifically applied to my s/n, to install an attenuator, and my log says that was done at last year’s annual (2021).
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jast
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Re: COM static

Post by jast »

Do you have third party devices attached to the USB/onboard power supply and/or transmit data? We had static issues with COM1 and rarely with COM2 in our DA62 because of a voltage converter from USB to 12V (step-ups are the worst!) in combination with a Golze ADL iridium modem. With a battery power supply it was 90% gone the rest came from the Irridium or LTE antennas…
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Boatguy
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Re: COM static

Post by Boatguy »

jast wrote: Sun Apr 10, 2022 9:54 pm Do you have third party devices attached to the USB/onboard power supply and/or transmit data? We had static issues with COM1 and rarely with COM2 in our DA62 because of a voltage converter from USB to 12V (step-ups are the worst!) in combination with a Golze ADL iridium modem. With a battery power supply it was 90% gone the rest came from the Irridium or LTE antennas…
We have no third party equipment. Some USB ports were added three years ago, but this problem is only in the last two months, since the annual.
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photoSteveZ
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Re: COM static

Post by photoSteveZ »

Boatguy wrote: Sun Apr 10, 2022 6:11 pm I'm getting lots of static on my radios when on the ground and a lower altitudes. It seems like the radios are super sensitive and have crazy static when nobody is talking, but I speculate that a very faint signal is being received. Sometimes the static triggers the Rx indication, but not enough to hear a voice. Sometimes just static and no Rx. It’s as though the squelch is set to some very low threshold, but I’m not aware of any way to set the squelch for the COM radios, other than ON/OFF.
I don’t have an airplane with G1000 avionics right to hand, but I recently learned you can adjust the Com squelch when it’s set to manual squelch, using the pilot’s volume knob on the audio panel. Similarly, you can adjust the intercom’s manual squelch (when the audio panel’s manual squelch is lit), for both the pilot and copilot/passengers. Can’t wait to try this, because I never figured it out when I had my ‘interim’ DA62.
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Boatguy
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Re: COM static

Post by Boatguy »

photoSteveZ wrote: Sun Apr 10, 2022 11:37 pm I don’t have an airplane with G1000 avionics right to hand, but I recently learned you can adjust the Com squelch when it’s set to manual squelch, using the pilot’s volume knob on the audio panel. Similarly, you can adjust the intercom’s manual squelch (when the audio panel’s manual squelch is lit), for both the pilot and copilot/passengers. Can’t wait to try this, because I never figured it out when I had my ‘interim’ DA62.
I knew you could adjust the squelch for the intercom, but not that you could adjust it for the COMs. That could be the explanation if somebody inadvertently twiddled a knob during the annual. Can you tell me the source for that? Was it in the Garmin manual?

It sounds like the procedure would be to push the COM volume knob for squelch, then twist for sensitivity?

I may go by my plane tomorrow and check that.

Thanks!
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arksat
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Re: COM static

Post by arksat »

Max Tresscott’s G1000 handbook says:
The G1000's COM radio squelch is set automatically so that the receiver is quiet when no signals are present. Sometimes, however, a weak signal may not be strong enough to open the squelch to enable the signal to be heard. Either the signal will break in and out or, if it's a weak signal, it's not heard at all. In this situation, pushing the VOL/PUSH SQ knob disables the automatic squelch so that the weak signal and its accompanying background noise can be heard. After you're finished listening to the signal, push the VOL/PUSH SQ knob again to re-enable the automatic squelch and remove the background noise.
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Boatguy
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Re: COM static

Post by Boatguy »

arksat wrote: Mon Apr 11, 2022 4:44 am Max Tresscott’s G1000 handbook says:
The G1000's COM radio squelch is set automatically so that the receiver is quiet when no signals are present. Sometimes, however, a weak signal may not be strong enough to open the squelch to enable the signal to be heard. Either the signal will break in and out or, if it's a weak signal, it's not heard at all. In this situation, pushing the VOL/PUSH SQ knob disables the automatic squelch so that the weak signal and its accompanying background noise can be heard. After you're finished listening to the signal, push the VOL/PUSH SQ knob again to re-enable the automatic squelch and remove the background noise.
That is push on/off. Steve is suggesting the squelch threshold can be set, not just on/off.
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mhoran
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Re: COM static

Post by mhoran »

You can use either automatic squelch (the default, documented in the quoted paragraph), or manual squelch. When you press the MAN SQ button, you control the squelch. I believe manual squelch resets to automatic on shutdown.

Regardless, in manual squelch the volume knob either controls volume, or squelch. This is indicated at the bottom of the audio panel: VOL vs SQ. Press the inner volume knob to switch between VOL and SQ when MAN SQ has been selected. Then use the inner knob to control squelch.

There is a light above MAN SQ to indicate it is active.
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Boatguy
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Re: COM static

Post by Boatguy »

The MAN SQ on the audio panel is for the intercom. My problem is with COM1/2.
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mhoran
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Re: COM static

Post by mhoran »

Boatguy wrote: Mon Apr 11, 2022 1:47 pm The MAN SQ on the audio panel is for the intercom. My problem is with COM1/2.
Might explain why it's never done what I thought it did.

Back to your original question. We had this for a while prior to performing the WAAS upgrade. We had the shop investigate and they found some loose connections to the COM antennas and replaced a bad GIA-63. That resolved the issue for a while. Then I had the WAAS upgrade performed and the issue came back. The shop again identified issues with grounding and supposedly fixed them, but I do still sometimes have this static. I think I also have some electrical interference somewhere that is intermittent. Perhaps during your annual some wiring was bumped that is causing the same for you.
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