On Sep 22, 9:47*pm, Darryl Ramm wrote:
On Sep 22, 8:19*pm, Larry wrote:

So I've got a mode-C xponder in my current glider. *Since I fly near
Reno airspace, when I get another glider I'll be installing a xponder
if it doesn't already have one.

Question- is there a reason why I would want a mode-S rather than a
mode-C?

Thanks,
Larry

Not really, in Europe Mode S is important. In the USA not so. Until
the TT21 my advice would have been to just by the cheaper Mode C like
the Becker 175W.

With Mode S you get a permanent aircraft ID so ATC can always tell who
you are. Some folks might not like that compared to Mode C. The Trig
will allow ADS-B data-out tricks in future but that is about a decade
from needing this. *The main thing with the Trig TT21 is that it is
easier to install, smaller, more power efficient and around the same
price as competing Mode C transponders and it is Mode S with "extended
squitter" support aka 1090ES/ADS-B data out for future possible use.
As I've said before the TT21 is a game changer and if it performs as
good in practice as it looks on paper it will do well. I currently fly
with a Becker Mode-C 175W (my second in two gliders I've owned). If I
was buying a new transponder today it would be the TT-21.

Darryl

Darryl,

I agree that the Trig appears to be a nice transpoder and reasonably
priced.

It does not appear to be any easier to install than a Becker or
Microair or have any better specs that the Microair or Becker in a
Mode C environment.

Trig 11min – 33 max Volts DC. Typical 5 Watts @ 14Volts.
Is the 11v acceptable in a Glider?

Becker 9.5 V to 32.2 V DC
Microair 10v to 33 v .15 to .200 amps
Trig 11 to 33 V .150 to .280 amps (from installation manual)

Low Power Design
The TT21 has one of the lowest power consumptions for any transponder.
With typical power consumption of around 5 watts, it can operate from
battery power for gliders or balloons for long duration flights. In
powered aircraft you can be sure that the TT21 is not making heavy
demands on your electrical system.

5 watts at 12 v = .41 amps
5 watts at 14v = .35 amps

Where did the .280 amps come from? I think all the manufactures play
with specifications.

An issue may be the temperature or the glider cockpit. The Trig
installation manual states The TT21 is certified to operate
correctly down to -20°C, but at low temperatures the display may be
impaired. On a cold day you may need to wait for the cockpit to warm
up to ensure normal operation.

All warranties are F.O.B.
Trig Avionics Limited Heriot Watt Research Park Riccarton, Currie,
EH14 4AP
Trig Avionics will not accept or pay for any charges for warranty work
performed outside our factory without prior written consent.

I perfer not to be a beta tester for a new instrument in the US
airspace environment. TSO only means they have completed the paperwork
requirements. I have experience the early problems with both Becker
and Microair. (They are now both reliable in the US airspace
environment)

Richard
www.craggyaero.com