When helping a friend install his AFS 4500 a few months ago, i could not
get his 396 to hold satellite reception when the 4500 was powered up.
Remembering a post by Vic S with the same issue, see here:
http://www.vansairforce.com/community/showthread.php?t=68725&highlight=antenna
We then moved the GPS antenna from the glare shield to the center bar
and the 396 worked as advertised. Knowing this issue, when I upgraded my 3500 to a 4500 this week, I moved my glareshield GPS and XM antennas from my 496 to under the cowling. Much to my dismay, the GPS would not maintain reception (XM is fine) with the EFIS powered up. So I moved the GPS antenna to the rear of my -8A. Now it worked great. Having not tried the GPS antenna on the glareshield at all, I was suprised to find on a test flight, that moving the puck back to the glare shield had no determental effect on reception. So now, i coiled the antenna wire behind the panel and moved the antenna puck back to the glareshield. Guess what.... no reception again. Seeing a pattern here, I moved the coiled antenna wire from behind the panel to the glare shield and low and behold satellite reception returned to normal. Because the GPS antenna is long, I had coiled the excess behind the panel when the GPS antenna was under the the cowling (the XM lead is much shorter and did not need to be coiled). I suspect the unshielded 496 GPS antenna lead while coiled and close to the EFIS was the problem all along, not having the puck on the glare shield.
PS... I love the SV in the AFS Advanced Deck 4500!
get his 396 to hold satellite reception when the 4500 was powered up.
Remembering a post by Vic S with the same issue, see here:
http://www.vansairforce.com/community/showthread.php?t=68725&highlight=antenna
We then moved the GPS antenna from the glare shield to the center bar
and the 396 worked as advertised. Knowing this issue, when I upgraded my 3500 to a 4500 this week, I moved my glareshield GPS and XM antennas from my 496 to under the cowling. Much to my dismay, the GPS would not maintain reception (XM is fine) with the EFIS powered up. So I moved the GPS antenna to the rear of my -8A. Now it worked great. Having not tried the GPS antenna on the glareshield at all, I was suprised to find on a test flight, that moving the puck back to the glare shield had no determental effect on reception. So now, i coiled the antenna wire behind the panel and moved the antenna puck back to the glareshield. Guess what.... no reception again. Seeing a pattern here, I moved the coiled antenna wire from behind the panel to the glare shield and low and behold satellite reception returned to normal. Because the GPS antenna is long, I had coiled the excess behind the panel when the GPS antenna was under the the cowling (the XM lead is much shorter and did not need to be coiled). I suspect the unshielded 496 GPS antenna lead while coiled and close to the EFIS was the problem all along, not having the puck on the glare shield.
PS... I love the SV in the AFS Advanced Deck 4500!