GNC355 Weak Transmit

Thanks for posting. Just so I understand, it wasn't the coax cable your installer originally used. It was the Mic Gain setting, not the carrier squelch setting? And you're sending it back for warranty replacement because the software keeps flipping it back to the default -12?
 
This is about the most frustrating thing in aviation: go for an upgrade, end up chasing your tail and wasting tons of money and brain damage in the process. Been there, done that, it sucks. Hope you get it figured out.
 
WDD said:
Thanks for posting. Just so I understand, it wasn't the coax cable your installer originally used. It was the Mic Gain setting, not the carrier squelch setting? And you're sending it back for warranty replacement because the software keeps flipping it back to the default -12?
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Yes, this is correct.

Update:

I contacted Garmin and they told me with my findings and they said that it sounded like a warranty issue. They asked that I go to a Garmin dealer, have them bench test it and then have them return the unit for warranty replacement.

The avionics shop tested and DID observe the fact that the settings would revert back to the wrong settings. Garmin swapped it out for a new one and, so far, things seem to be working just fine.
 
I wonder if I could get the serial # of your old unit as I think Garmin may be reboxing and I may have a previously bad unit. My unit is intermittent also.
Garmin is sending a new unit to my installer too.
I hope this does the trick.
 
The issue reappeared tonight! So, afterwards, I went into settings and set it to the known-good settings I sent you the pic of. We'll see if it holds.
Unbelievable. I had to switch to my KX170b the volume was so bad through my mic.
I have no idea what my SN was for the old unit (wouldn't that be something???)
 
+1 for low transmit power on newly installed GNC355

Comm 2 loud and clear
New audio panel from ps engineering
New antenna

any news on this front?
 
Im having this issue on my GNC355 that was installed a few months ago. I thought maybe it was an audio panel issue but I just had a new PSE 450b installed and it is still a problem. Ill check my mic gain.
 
Has there been a fix to this issue. I have a GNC355 and Get Loud and Clear, and then out of know where no one can here me. What are the correct COM settings for this to work?
 
This was the fix from my avionics installer and it worked fine.



I called Garmin, and I think that it is the mic gain setting for the GNC 355. Since I will be off next week, I will walk you through the steps to adjust that.

First, get into configuration mode, starting with the unit powered down.
The Configuration mode of the GNC 355( ) can be accessed by holding down the inner knob located at the
bottom-right of the unit and pressing the Power/Home button. When the Configuration mode home page displays, release the knob.

From there you will see six tiles or buttons, select the Setup button. then select the COM button in the next menu.

From here, select the Mic Gain Button which can go from -12dB to 30dB.
This will adjust the gain of your microphone for your Com Tx. If it is too low, your transmit will be received quiet, if too high, then it will sound distorted.

Please increase the gain as necessary.
You will also see sidetone volume in that menu, you can adjust it if you feel that your sidetone is too loud when you transmit.
 
Can someone post a pic of known good settings or just post a reply. My mic gain was at -12 and I changed to +12 and it helped but still having intermittent transmit and receive issues. Rx sq config 75% and carrier sq 55% mic gain +12.
Thanks
 
Get your antenna and coax swept by an avionics tech that knows what that is and how to do it. The mostly likely reason for “weak and unreadable” is a high swr reading. And if you don’t get it fixed it’ll burn up your radio.
 
Mjhworth said:
Can someone post a pic of known good settings or just post a reply. My mic gain was at -12 and I changed to +12 and it helped but still having intermittent transmit and receive issues. Rx sq config 75% and carrier sq 55% mic gain +12.
Thanks
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I have a similar issue. I saved a photo of the “good” settings per the avionics shop.
 

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Thank you for the feedback. A little more info on my installation. Nothing was reused. New Ram antenna (actually 2nd Ram antenna since the first failed after a few flights) all wiring, bonding, and coax new. The installation has been gone through and tested thoroughly. Next steps may do another antenna coax sweep and have Garmin do a bench check. Will double check my settings. May lower both squelch a bit to see what difference it makes.
 
What kind of inline filter? Just installed a 355 and have limited range. I need to go back and check the squelch settings as mentioned elsewhere here. We have a TED 4-70 notch filter installed for GPS interference.
 
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