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

Hi Morteza
I have the Trig21.
Installed myself in my experimental to replace a Terra250.
Had no problem to get it signed-off at standard price at Precision
Static in Livermore.
Very happy with it.
Reno sees it very well, even at 18k. No issue with the output power.

When the PowerFlarm arrives, I suspect that suddenly there will be a
miraculous unexplained wire in my harness.
I guess that wire will be carrying 19200 baud NMEA sentences from the
PowerFlarm to the Trig21 and the Trig will be squittering 1080ES ADS-B
Out after someone accidentally toggled the setting in the setup menu
to enable this feature.
Of course I have nothing to do with this. I will stay legal.

I got a good price from Tim M. Better then mentioned above.

You can see my installation he
https://sites.google.com/site/threeu...21-transponder
Or you can have a look at my ship at Tahoe (or soon down the hill)

3U

On 9/12/11 6:43 PM, weersch wrote:

Hi Morteza
I have the Trig21.
Installed myself in my experimental to replace a Terra250.
Had no problem to get it signed-off at standard price at Precision
Static in Livermore.
Very happy with it.
Reno sees it very well, even at 18k. No issue with the output power.

When the PowerFlarm arrives, I suspect that suddenly there will be a
miraculous unexplained wire in my harness.
I guess that wire will be carrying 19200 baud NMEA sentences from the
PowerFlarm to the Trig21 and the Trig will be squittering 1080ES ADS-B
Out after someone accidentally toggled the setting in the setup menu
to enable this feature.
Of course I have nothing to do with this. I will stay legal.

I got a good price from Tim M. Better then mentioned above.

You can see my installation he
https://sites.google.com/site/threeu...21-transponder
Or you can have a look at my ship at Tahoe (or soon down the hill)

3U

OK I think you fall into the "technically competent" subcategory (even
with the 1080ES typo) :-)

Darryl

Thanks everyone for the feedback. I am convinced (again) that TT21 is
the best option. I will make sure I build the harness with the wires
for the GPS input and ADS-B out just in case. I will order one along
with the L2 antenna. I had great success with it in the previous
installation and they are so easy to install pretty much anywhere.

Now if I figure out what to do with the flight computer, I am all set
for redoing the panel layout and getting to work


Cheers,
Morteza

OK I think you fall into the "technically competent" subcategory (even
with the 1080ES typo) :-)

Darryl

Thanks Darryl for my induction in your hall of "technically
competent". I feel honored.
Yeah, doing too much 1080P work and not enough 1090ES.
3U

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

Eric Greenwell wrote:
What regulation makes it illegal for a glider to use the TT21 between
15,000 and 18,000'?

Of course it's not illegal to turn on a class 2 transponder above 15,000
feet. But with a class 2 transponder, you can't tell ATC above 15,000
feet that you're transponder equipped, because legally, you're not.
Where I fly, I pretty routinely enter protected airspace at that
altitude, and I would hardly get a clearance without a transponder. This
has been the main reason for me to buy a transponder, so buying class 2
transponder would have been pretty pointless.

I don't care whether "they" would notice or not that I carry only a
class 2 transponder. The price gap of a mere $200 is far too small to
even consider to cheat.

Of course all depends on where you fly and to whom you want to sell your
glider later. So all I've wanted to say is that when you consider to buy
a class 2 transponder, be aware of the limitation.

John Smith wrote:
Eric Greenwell wrote:
What regulation makes it illegal for a glider to use the TT21
between
15,000 and 18,000'?

Of course it's not illegal to turn on a class 2 transponder above
15,000 feet. But with a class 2 transponder, you can't tell ATC above
15,000 feet that you're transponder equipped,

Ah you want to show us a regulation or chain of regulations that says
that? Which country are you flying in? You keep using the word legal and
illegal etc. In the USA the FARs actually do not appear to place clear
requirements in this area on the PIC. Show us the regulations please...


And just for kicks 14CFR 91.215(c) "Transponder on operation" requires a
pilot say who climbs above 15,000' with a class 2 transponder to keep
operating that transponder.

because legally, you're not. Where I fly, I pretty routinely enter
protected airspace at that altitude, and I would hardly get a
clearance without a transponder. This has been the main reason for me
to buy a transponder, so buying class 2 transponder would have been
pretty pointless.

And buying class 2 would likely have made no difference to any if that.


I don't care whether "they" would notice or not that I carry only a
class 2 transponder. The price gap of a mere $200 is far too small to
even consider to cheat.

Of course all depends on where you fly and to whom you want to sell
your glider later. So all I've wanted to say is that when you consider
to buy a class 2 transponder, be aware of the limitation.


and that's all fair but the more important thing is getting pilots in
key high traffic areas to equip and use transponders (of any class or
type)). And for most pilots in the USA it is not about clearances, it
is about avoiding an encounter with an airliner or fast jet.

Darryl

If you intend to use any smart PCAS (e.g. PowerFLARM) you want a Mode-
S, since suppressing your own transponder signal is a lot easier and
more reliable if the source is a Mode-S.
Other PCAS are also somewhat more likely to make sense of your
transmissions.
So do yourself and the World a favor and buy a Mode-S.

Ironically your decision is between buying into technology of the
fifties vs. the seventies...

Enjoy
Urs