After going to OSH this year to look at ADS-B out for my RV-4 I decided to continue waiting (BTW I think every RV that was built was there). I have a used Garmin 696 with a GL-39 antenna so I am doing fine with ADS-B in. A lot of my questions were answered but more were raised along with some confusion. I would like to keep it at or under $1k and simply refuse to put in a system that costs more than 10% of the total value of my plane particularly since I rarely fly in controlled airspace any more. I was leaning toward the Echo UAT or the Beacon 978. What ticks me off is that they tell me (or in some cases wouldn?t tell me) that they need an additional $300 to $500 WAAS antenna. Does anyone know if one of those Globalsat BU353 SiRF Star III USB GPS Receiver Antenna can be wired into these transmitters and if so what is the wiring diagram?