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David,
The mode S transponder Bill suggested cost is about $2300 including the control head or $1800 without control head. They do support the 1090ES protocol for ads-b "out" so this option would give you the minimum required equipment when ads-b becomes mandated (and meet ICAO requirements for flying outside the US). (of course this requirement could change by 2010). This option also gives you traffic. IF you go the UAT route, then you have ads-b "in" and "out". This gives you traffic (TIS-B), all weather(FIS-B) much like XM or WSI, plus your UAT communicates directly with other UAT airplanes so even if you are below radar coverage you will see other airplanes if they are ads-b equipped. If you fly in areas that have ads-b coverage now, then I'd highly suggest you go the UAT route with a standard transponder. With a mode S transponder, you will get TIS-B traffic in areas where it's offered but this system will not be upgraded and will be phased out making a standard mode S transponder no better than a standard cheap transponder. Garmin offers a 1090ES mode S transponder but it's much more expensive than a GTX330. The 1090ES (extended Squitter) transmits your gps position (and a few other things). every time your transponder is interogated. The ads-b coverage is growing daily and probably covers a lot more area right now than most people think. Pretty much the entire East coast, all of FL, all of S. CA, and a huge area of the Gulf of Mexico is currently active (much more of course across the US).
I know this was a pretty quick answer to a sort of complex question but hope you get the idea. If you want to discuss it with me directly I'd be glad to. This was one of the areas that I worked on during my time at FAA HQ in DC. There are still a few questions as to what the final requirements will be for GA airplanes but a standard transponder plus a UAT will give you the best bang for the buck. If you want to wait for more UAT options, then just a standard transponder is the best option. If you have TCAD then you really don't need the mode-S transponder.
Ron
----- Original Message -----
From: Dr. Weinsweig
Sent: 07/21/11 07:50 AM
To: lml@lancaironline.net
Subject: [LML] mode s and ads-b compliance and upgrading transponders
howdy all,
my remote sl70 transponder(controlled by cnx80) has stopped working properly and i am going to modernize my transponder system. i have never really been real happy with remotely controlling the transponder. every once in a while the cnx80 would say "cannot command transponder" but with a reboot it would always work. we have made room for a transponder in the panel by removing a dvd screen in front of the copilot which was never used(seemed like a good idea at the time-thanks kirk hammersmith!).
the plan is to put a gtx327 in the panel with the possibility of adding a 2nd (remote transponder to be controlled by the cnx80) down the road. as a backup.
i have tcad and wsi weather. as best as i can tell the requirement for mode s and ads-b will not be in place until 2020. thus i really cannot see any justification to going with a more expensive transponder than the gtrx327 at this time as i don't need the tis capabilities of the gtx330 and my experience with avionics is that it is outdated almost by the time it is installed and who knows what will really happen with mode s and ads-b?
am i correct in these assumptions or should i spend more cash for a higher end transponder with more capabilities? also, is it worth it to spend the cash and have a backup transponder now?
suggestions?
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