RF noise and Garmin 650

[dpbarnes]

I just finished an avionics upgrade that included replacing a sl30 with a Garmin 650.  I ended up unable to squelch the 650 no matter what squelch settings I used.  The only exception was the frequencies between 133 and 136 did squelch but as I got lower it got worse.  I have an all fiberglass airplane (lancair es) with two antennas.  One mounted on the belly with internal copper strips for a backplane and one dipole style mounted in the vertical stabilizer.  To confirm the noise was coming in the antenna I put a dummy load on the 650 and the radio noise was gone.  Even at the lowest squelch setting.  I tried many cures but nothing had much effect.  Shutting down the two 10" screens solved the problem but made it hard to fly. So I switched antennas.  I put the belly antenna on the sl40 and the vertical stabilizer antenna on the 650 and all was fine.  I posted this to let people know that there is some rf noise coming out of the skyview and it can interfere with the com radios maybe worse in fiberglass airplanes and the squelch level in garmin's new 650 can't be adjusted as high as it can be in the sl30 and sl40 radios. Moving the antenna as far away from the screens seems to have the most effect.

 

[Carl_Froehlich]

I've gone around the tree several times solving all the problems I've had with my GTN-650. After you do the normal stuff like making sure all your leads to the 650 and audio panel are shielded, your antennas are in fact tuned to the correct frequency (don't just install them - tune them as well), your antenna connectors are sound, etc, then contact your favorite avionics shop for the RFI filters available for the 650. It seems many people need to use them.