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  #1  
Old 12-08-2019, 10:52 AM
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n38139 n38139 is offline
 
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Default GARMIN GMA 240 PANEL

I have a GMA 240 and it has a lot of for the lack of a better term "white noise" when I turn it on. It is not alternator, or ignition noise. In fact, with everything off except the avionics, it is still there. When I turn it off, and transmit on my 430W there is NO noise in the audio at all. It's white noise only there when I have the 240 turned on. I have adjusted the intercom, thought it might be that, no effect. I've pushed every button on it and no effect. I tried a friend of mines PS engineering panel in the rack and it is at least 1/2 the noise as the 240. Anybody have any ideas?

thx
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  #2  
Old 12-08-2019, 11:41 AM
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Quote:
Originally Posted by n38139 View Post
I have a GMA 240 and it has a lot of for the lack of a better term "white noise" when I turn it on. It is not alternator, or ignition noise. In fact, with everything off except the avionics, it is still there. When I turn it off, and transmit on my 430W there is NO noise in the audio at all. It's white noise only there when I have the 240 turned on. I have adjusted the intercom, thought it might be that, no effect. I've pushed every button on it and no effect. I tried a friend of mines PS engineering panel in the rack and it is at least 1/2 the noise as the 240. Anybody have any ideas?

thx
Hello Steve,

The first step is to determine the source of the "white noise".
  1. Is this "white noise" loud enough that you can hear it in flight?
  2. Have you tried turning on/off any ANR capability on your headset and see it that affects this noise?
  3. Do you fly with your headset volume knobs turned all the way up so you can turn down the volume/gain of the intercom and other audio sources?
  4. When you power on the GMA 240 by itself, with nothing else in the plane powered up, do you still hear the noise in the pilot headset? What about the copilot headset?
  5. Have you made sure to power off all potentially noisy USB power sources?
  6. Your GMA 240 has 3 unswitched alert audio inputs, each with individual volume adjustments. Is anything connected to these inputs? If you power off the devices connected to these inputs does the noise go away?
  7. Does the noise respond to intercom volume adjustments (get louder/softer) with intercom volume adjustments for either pilot or copilot, or stay at the same level?
  8. Have you verified that the intercom squelch is properly adjusted for both pilot and copilot? Is the pilot or copilot intercom squelch turned all the way down and is thus "open" all the time (whether or not a headset mic is plugged in)? A GMA 245 has auto-intercom squelch, but this is manually adjusted on the GMA 240 for both headsets.
  9. When you hear the white noise, have you turned off all the AUX, NAV, music, telephone, and other pilot selectable audio inputs to try to isolate the source?

An adjustment of the Master Avionics Squelch (MASQ) mute level is seldom needed (or recommended), but if you have electronic noise that is exceeding this threshold, you could try adjusting this as explained in the manual.

Please contact us directly if you would like our assistance.

Thanks,
Steve
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  #3  
Old 12-09-2019, 02:07 PM
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n38139 n38139 is offline
 
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Default

I've done most of what you asked, I will do the other pieces when I go back out to the hangar.

thx
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  #4  
Old 12-09-2019, 04:35 PM
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Originally Posted by n38139 View Post
I've done most of what you asked, I will do the other pieces when I go back out to the hangar.

thx
Hello Steve,

Sounds good.

I have flown GMA 240 and GMA 245 audio panels for 11+ years, and they have always been super quiet.

We use the Bluetooth audio from the GMA 245 in 2 flight test aircraft on every flight to provide the same audio that the pilot hears to the Virb Ultra 30 camera. The flight video is so quiet between intercom and radio activity that until you hear the first audio, you wonder if it has recorded any audio on that flight.

After reading the above report, we tested a GMA 240 to see if we could come up with any elevated background noise scenarios. The only thing we came up with was to pull out the right knob (music volume adjust), turn the music volume all the way up with no music source connected, and turn music on with the dedicated music on/off button. It is doubtful that anyone would ever do this, but it was the only scenario we could come up with that would cause elevated background "white noise".

As many know, we are proponents of creating high audio signal to noise ratios such that the system never ends up significantly amplifying any noise that might be present on an audio input. This is done by using relatively high volumes at the alert, music, and radio audio source, which results in using very low volume settings and low amplification at the audio panel.

Thanks,
Steve
__________________
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g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.
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