I recently mixed up my COM and GPS antennas on my GNC 300XL and blew
the GPS antenna. Garmin wants $386 for the replacement GA56 antenna. I
took a chance an purchased a universal GPS replacement amplified
antenna for $20 on ebay - http://cgi.ebay.com/ws/eBayISAPI.dll...m=120158358512
-
and it works. You can also get a used GA56 for about $60 on ebay. I
think $386 is outrageous.