Dropping satellites

Jim Wells

Recently my 430 has been dropping satellites when I transmit using the 430W Comm. I"ve always had this problem when transmitting using my #2 Collins Comm but never with the 430 'til now. Just curious if anyone else has experienced this problem.
Thank you.

Bob H

Hi Jim, The GNS-430W is a lot more sensitive to "interference" than the original non-WAAS 430's. We went "nuts' when we
did our first upgrade from a non-WAAS to a WAAS unit in a customer's Baron. The same thing happened. If you look at the GPS signal strength, it drops off when you key the mic. We spent two weeks trying to work out the solution. What we discovered is that the 430W, at transmit was creating a "harmonic" with the aircrafts ELT and existing comm antenna locations. This is amazing because, obviously, the ELT is off! In this case, we had to install a filter on the ELT antenna and move one of the aircrafts comm antennas until it finally worked. If you have upgraded your non-WAAS 430 to a WAAS version and just put it back into the original installation, I won't always work! Note that the 430W TSO requires the use of a double sheilded antenna cable. It is required to change that if the original install did not have double sheilded cable. If I read your post correctly, you have a 430W and a non-WAAS 430 in the aircraft? Did you recently add something to the panel or the aircraft? Did you put in a 406 ELT maybe? Add or move an antenna? Sounds like the comm transmit is "flooding" the GPS signal? Good luck. Bob Hart APG-Eastern Avionics.

Jim Wells

Thank you Bob. I have just the one 430 that was upgraded to WAAS a couple of years ago. I did talk to Garmin and another avionics shop. You're right about the ELT. When I disconnect the coax from the ELT unit the problem goes away. They think I need a notch filter for the 430 from Garnin. About $45. Guess I'll go that route.
I appreciate your response very much.

Jim Wells

I installed the notch filter. No improvement. What's interesting is the notch filter, P/N 330-00067-00, is a mechanical device and looks like a BNC "T" connector.

Maj Geezer

Hi guys just my .02 worth. Had a similar problem that was difficult to unravel and it all started with a new ELT antenna that was a little taller than the old one. It was not far from my rear dorsal comm antenna. The solution was to move that comm to the belly and all was right with the world. That is the short version of the tale Good luck

Avionics-tech

Jim

The notch filters never work. In some cases they make it worse. The coax cable length has an effect as well.

The problem is the ELT. This has been know for over 20 years. RF from the transmitting antenna is received by the ELT antenna, enters the ELT, get rectified by a junction device and gets back out as a nuisance harmonic. Specific ELT's are the culprits. This phenomena also occurs when flying in the vicinity of high powered transmitting towers. The Pointer is by far the worst. The Ameriking is also a problem. The only solution is the change the ELT. Borrow a few different types and try them before you commit. If you upgrade to a 406, the Kannad seems to work well.

Jim Wells

Thanks everyone for the excellent info.