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#1
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Transponder: Mode-C or Mode-S?
I recently bought a new bird and need to put a transponder in it. The
choice was obvious (until I took a closer look). Trig TT21 seems like a great choice: small footprint, built-in encoder, 1090ES ADS-B out, and descent price. However a bit more looking revealed more questions than answers. It seems it requires an ISO GPS and one could not use typical GPS sources we have in gliders, it is not clear if the ADS-B out work with PowerFLARM (at least from what I have heard), and the biannual testing cost 2-3x as much as mode-C. Any thoughts/suggestions from more knowledgable folks? Cheers, Morteza |
#2
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Transponder: Mode-C or Mode-S?
Morteza Ansari wrote:
I recently bought a new bird and need to put a transponder in it. The choice was obvious (until I took a closer look). Trig TT21 seems like a great choice: small footprint, built-in encoder, 1090ES ADS-B out, and descent price. However a bit more looking revealed more questions than answers. It seems it requires an ISO GPS and one could not use typical GPS sources we have in gliders, it is not clear if the ADS-B out work with PowerFLARM (at least from what I have heard), and the biannual testing cost 2-3x as much as mode-C. Any thoughts/suggestions from more knowledgable folks? Cheers, Morteza The TT-21 as a Transponder utterly blows away any other transponder available in the USA for use in gliders. it's power consumption, split box install options, built in encoder, etc. are totally compelling by themselves. You should think of this as a Mode-S transponder today. That does not use/need any GPS source. The 1090ES data-out capability is really there for future use. And exactly what features/compliance you are aiming for there is a longer discussion. You should think of ADS-B as a future thing, not something here today. Many ADS-B devices require upgrades to meet the 2020 mandate specs, and to meet this full spec (remember gliders are exempt) you must use aviation (not consumer) style GPS sources. You cannot currently install any ADS-B data-out in any certified aircraft including certified gliders without a STC approval, and since the FAA is unlikely to grant an STC for an install with a non Aviation/WAAS GPS that would today mean spending several $k to include that GPS-and finding somebody to develop the STC. Those GPS prices will fall in future and the STC requirement will go away. But if the FCC ever allows a field approval install for a non-aviation GPS as a data-source on a certified glider who knows (but don't hold your breath). This while area is a mess at the moment and just not worth most glider pilots losing sleep over. Technically sophisticated folks who understand this stuff and who fly experimental gliders today have other options including using non-certified GPS sources. Setting this up is described in the Trig manuals. If you are having to ask questions about this my inclination is you should just install the TT-21 as a Mode-S transponder today. I do not understand your specific concern about compatibility with PowerFLARM. You need to clue us in to "what you have heard" if you want cogent comment on that. PowerFLARM today will see/display other 1090ES data-out equipped aircraft but will not provide an alarm for any threats with those aircraft. That is coming in a future update. None of that is specific to using a TT-21. There are _very_ few 1090ES data-in equipped aircraft around right now so this is not a big issue and other PowerFLARM equipped gliders will see you via FLARM-FLARM anyhow. The basic Mode-S (or Mode-C) transponder by contrast is seen by ATC, by TCAS which is widely used in airliners and private jets, military transports, many tactical military aircraft etc. and TCAD in some GA aircraft and by PCAS systems used widely in lower end GA aircraft. It is the 21st century buying a Mode C transponder makes _no_ sense. You might be able to find a different test provider - not all uplift so much for a Mode-S. There is no valid reason for such an inflated cost. Some will do great deals to come to the gliderport/ramp and test a whole fleet of gliders in one day. Darryl |
#3
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Transponder: Mode-C or Mode-S?
Darryl Ramm wrote:
The TT-21 as a Transponder utterly blows away any other transponder available in the USA for use in gliders. Just be aware that the TT21 is a class 2 tansponder, i.e. not certified for use above 15,000 feet, and therefore not suited for gliders. Buy the TT22 instead which is class 1. |
#4
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Transponder: Mode-C or Mode-S?
Using the same logic, don't buy anything other than V rated tires for
your car, as the common S rating is only good for 112 mph (180 kph). -John On Sep 12, 7:55 am, John Smith wrote: Just be aware that the TT21 is a class 2 tansponder, i.e. not certified for use above 15,000 feet, and therefore not suited for gliders. Buy the TT22 instead which is class 1. |
#5
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Transponder: Mode-C or Mode-S?
John Smith wrote:
Darryl Ramm wrote: The TT-21 as a Transponder utterly blows away any other transponder available in the USA for use in gliders. Just be aware that the TT21 is a class 2 tansponder, i.e. not certified for use above 15,000 feet, and therefore not suited for gliders. Buy the TT22 instead which is class 1. This has been discussed here a lot before. the power difference will make no practical difference. By all means pay slightly more and install the TT22 but the important thing is for folks that fly in busy airspace near airliners etc. to have a transponder (and even an older Mode C transponder works fine fir that). Most transponders installed in gliders in the USA appear to be class 2. Darryl |
#6
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Transponder: Mode-C or Mode-S?
Am 12.09.11 14:57, schrieb jcarlyle:
Using the same logic, don't buy anything other than V rated tires for your car, as the common S rating is only good for 112 mph (180 kph). If I wanted to drive with 112 mph (180 kph), then you'd be perfectly correct. Glider pilots on the other hand tend to want to climb as high as they can. In fact, the possibility to get a clearance to climb has been the main reason for me to buy a transponder. So it would have been pretty pointless to buy a class 2 transponder. As always YMMV, but at least one should be aware of this limitation before spending money on a class 2 transponder. |
#7
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Transponder: Mode-C or Mode-S?
On Sep 12, 7:07*am, Stefan wrote:
Am 12.09.11 14:57, schrieb jcarlyle: Using the same logic, don't buy anything other than V rated tires for your car, as the common S rating is only good for 112 mph (180 kph). If I wanted to drive with 112 mph (180 kph), then you'd be perfectly correct. Glider pilots on the other hand tend to want to climb as high as they can. In fact, the possibility to get a clearance to climb has been the main reason for me to buy a transponder. So it would have been pretty pointless to buy a class 2 transponder. As always YMMV, but at least one should be aware of this limitation before spending money on a class 2 transponder. Except for the fact that the folks on the ground that grant the clearance don't know or care whether you've a Class 1 or Class 2 transmitter as long as they are receiving your signal. They also don't care about you when you are more than 40 miles out, and if 135 watts won't get you 40 miles, something's wrong with your installation. A properly installed* Class 2 with a dipole antenna in a fiberglass (not carbon) fuselage glider will get more radiated power out than most GA with metal fuselages and the 1/4 wave monopole antenna they are forced to use. If you've got a carbon fuselage, you're stuck with the 1/4 wave. * a major contributor to lost outpout power is the cable from the transceiver to the antenna. Don't use RG-58. It's unsuitable for L- band. |
#8
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Transponder: Mode-C or Mode-S?
jim wynhoff wrote:
Except for the fact that the folks on the ground that grant the clearance don't know or care whether you've a Class 1 or Class 2 The price of a TT22 vs TT21 is about $2500 vs $2300 (approx.). This $200 to $300 gap isn't nearly big enough for me to even start to think about going the illegal route. As always YMMV. |
#9
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Transponder: Mode-C or Mode-S?
On 9/12/2011 8:32 AM, John Smith wrote:
jim wynhoff wrote: Except for the fact that the folks on the ground that grant the clearance don't know or care whether you've a Class 1 or Class 2 The price of a TT22 vs TT21 is about $2500 vs $2300 (approx.). This $200 to $300 gap isn't nearly big enough for me to even start to think about going the illegal route. As always YMMV. What regulation makes it illegal for a glider to use the TT21 between 15,000 and 18,000'? Does it make a difference if the glider is licensed "Experimental"? Even if it is illegal, can we at least agree it is entirely suitable for it's intended purpose: providing ATC and TCAS a glider's position and altitude? -- Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me) - "Transponders in Sailplanes - Feb/2010" also ADS-B, PCAS, Flarm http://tinyurl.com/yb3xywl |
#10
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Transponder: Mode-C or Mode-S?
Out of four different transponder and encoder combinations I've used
in gliders (Garmin/TransCal, Terra/Terra, 2x Becker/ACK, 2x Trig) the Trig has proven to have the least power consumption. The Trig is easy to install if you buy your own D-Sub connectors or a crimp tool for the included ones, or have someone with a crimp tool build the harness for you. The small Trig control panel may fit in a corner of the panel you thought unusable. RG58 antenna cable worked fine for me (even with a TNC to BNC adapter), but total cable length is less than 10' / 3m. For longer runs you'll do better with something lower loss. Joshua and Oakland have had no trouble getting radar contact with the Trigs. At the three avionics shops I called about Mode S, cost was the same to certify Mode C or S transponders. I believe the Trig takes less time if any adjustments are needed, but in my experience they haven't required adjustment. The altimeter is the most likely thing to require adjustment. And it's Scottish, so it can't be crap! Jim |
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