> Sent: Friday, March 13, 2015 at 9:56 AM > From: "Bill Masquelier via KRnet" <krnet at list.krnet.org> > To: "KR List" <krnet at list.krnet.org> > Subject: KR> KR transponder? > > We are getting our KR2 close (year or two) to completion- > in our area we will need a transponder (San Diego) > We may as well go with a "mode S" since it will be required soon. > What is the collective opinion of the group for a "modestly priced" one that > will work for us? > Bill Masquelier
Bill, Since the others on here have cleverly suggested used mode C transponders rather than answering your question, I'll give this a shot. If you're looking for a Mode S transponder that will be compatible with the ADS-B out equipment, I would suggest buying a Trig, either a TT22 or TT31 depending on panel space available. The TT21 will also do 1090-ES, but the broadcast power doesn't meet the 2020 standard. The Trig TT22 without a face is also the transponder of choice used in conjunction with the Dynon Skyview Avionics suite. Of course your other option would be to go with a compact Mode C transponder and a UAT ADS-B out unit like the NavWorX unit. If you are starting with a clean slate for an installation, it will be less expensive to equip with mode-S (1090-ES) than to buy a mode C transponder, then add a compliant UAT transmitter. We did some ADS-B performance testing last weekend while traveling from Tucson to Los Alamos. The FAA now has an email address you can email some basic data and they will check your last flight with ADS-B out and email you a report on the performance of your ADS-B unit. We tested my Skyguard TWX and a Dynon Skyview with a Trig TT22 mode S transponder. The Skyguard unit meets the performance standard, but fails to meet the ADS-B rule because it doesn't have pressure altitude as part of it's broadcast. That is a problem come 2020 as their current units don't have any methodology for adding pressure altitude. The Dynon Skyview unit with the Mode-S Trig transponder meets the ADS-B rule, but failed to meet the performance standard due to the inaccuracy of the Dynon GPS unit. That can be easily corrected with a new GPS puck, which Dynon will undoubtedly be offering. For today, if one was planning to use a mode-C transponder and a UAT out (which I wouldn't recommend for a new installation), I would use the NavWorx unit. It is listed at $799, but you'll find once you get done equipping it to actually work, you'll have roughly $1600 invested. The NavWorx unit can be used with an inductive pickup that goes around your transponder coax cable to pick up your pressure altitude and squawk code for retransmit in the UAT Out signal if you don't want to have to run a gray code cable to the unit. -Jeff Scott Los Alamos, NM
