Face it, transponders live tough lives. Their high power out generates lots of heat in the radio stack and ultimately that takes a toll on internal components. So when searching the used market for a sweet deal on a transponder, choose wisely. One slam-dunk winner could be the discontinued Garmin GTX 327.
This is an all-digital Mode A/C model that was a popular pairing with the Garmin GNS navigator and has a good service record because of its solid-state design and rugged control set. Plenty still exist, but many are being removed for a relatively easy transition to Garmin’s flagship ADS-B Out GTX 345.