175 or 250 watt transponder?

Needing a replacment, my transponder shop told me that above 15k' the
FAR's require a 250 watt transponder (125w below 15k').

True?

I'm pretty sure that sailplane owners are mostly installing 175 watt
units and flying them to 18k' (and higher in wave windows). Right?

If this 15k' rule is real, I'm supposing that, since gliders aren't
required to have a transponder except in certain airspace (this
airspace is all below 15k' -- except Class A...) that we're generally
free to install anything we want (except 18k' in Class A?).

Bottom line -- 175 watts or 250 watts?

Eric Rupp
ER
(My Terra TR250D transponder is inop and I'm having trouble getting
parts - anybody have a dead one that we might be able to salvage from?)

On Jan 8, 1:01*pm, Itsaplane wrote:
Needing a replacment, my transponder shop told me that above 15k' the
FAR's require a 250 watt transponder (125w below 15k').

True?

Eric,

Have you tried Freeflight?

http://www.freeflightsystems.com/index.htm

Mike





I'm pretty sure that sailplane owners are mostly installing 175 watt
units and flying them to 18k' (and higher in wave windows). *Right?

If this 15k' rule is real, I'm supposing that, since gliders aren't
required to have a transponder except in certain airspace (this
airspace is all below 15k' -- except Class A...) that we're generally
free to install anything we want (except 18k' in Class A?).

Bottom line -- 175 watts or 250 watts?

Eric Rupp
ER
(My Terra TR250D transponder is inop and I'm having trouble getting
parts - anybody have a dead one that we might be able to salvage from?)

On Jan 8, 12:17*pm, Mike wrote:
On Jan 8, 1:01*pm, Itsaplane wrote: Needing a replacment, my transponder shop told me that above 15k' the
FAR's require a 250 watt transponder (125w below 15k').

True?

Eric,

Have you tried Freeflight?

http://www.freeflightsystems.com/index.htm

Mike



I'm pretty sure that sailplane owners are mostly installing 175 watt
units and flying them to 18k' (and higher in wave windows). *Right?

If this 15k' rule is real, I'm supposing that, since gliders aren't
required to have a transponder except in certain airspace (this
airspace is all below 15k' -- except Class A...) that we're generally
free to install anything we want (except 18k' in Class A?).

Bottom line -- 175 watts or 250 watts?

Eric Rupp
ER
(My Terra TR250D transponder is inop and I'm having trouble getting
parts - anybody have a dead one that we might be able to salvage from?)- Hide quoted text -

- Show quoted text -

Freeflight does no service the Terra transponder, but Gulf Coast
Avionics in Lakeland , Florida does . They can be reached at
863-709-9714.

Ramy

Bottom line: If you want to fly above 15k in airspace where a
transponder is mandatory, then 250W is required or you will not fly
there. Otherwise install whatever you want. As there is little
difference in price as well as in power consumtion, I don't see why you
would want to go for the weaker unit, though.

A side note: If you want to stick with a mode C transponder, then there
are a lot of used ones available in Europe pretty cheaply, as Europe is
mandating mode S now and everybody must switch. If on the other hand you
want to buy a new unit, then go for mode S. It doesn't cost much more,
it draws less current and it will have a much better resell value.

John Smith wrote:
Bottom line: If you want to fly above 15k in airspace where a
transponder is mandatory, then 250W is required or you will not fly
there.

Do you have a reference to the regulation concerning power requirement?
I haven't been able to find it, and people just seem to rely on the
product descriptions when I ask about it.

hough.

A side note: If you want to stick with a mode C transponder, then there
are a lot of used ones available in Europe pretty cheaply, as Europe is
mandating mode S now and everybody must switch. If on the other hand you
want to buy a new unit, then go for mode S. It doesn't cost much more,
it draws less current and it will have a much better resell value.

Can you tell me which Mode S transponder you are talking about? The ones
that I see for sale in the USA are much more expensive ($600 comparing
the 175W and 150W models of Becker; $1100 comparing the 250W models of
Becker).

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

Eric Greenwell wrote:

Do you have a reference to the regulation concerning power requirement?
I haven't been able to find it, and people just seem to rely on the
product descriptions when I ask about it.

Actually, I do, too. I see no reason not to believe the manufactorers.
According to Funkwerk, output requirements are higher for tansponders
which are operated in aircraft flying at altitudes above 15,000ft or
speeds above 175kt. Unfortuately (of fortunately), gliders often operate
higher than 15,000ft.

I write this with the European situation in mind where Mode S is already
mandatory. As air traffic is typically an international thing, I would
assume that the FAA and EASA have been reasonable enough to discuss this
and to agree to the same requirements.

BTW, problably not the cheapest but one of the more popular mode S
transponders in Europe is the TRT800H by Funkwerk.
http://www.funkwerk-avionics.com/cms...4&changelang=4

On Jan 9, 1:12*am, John Smith wrote:

Actually, I do, too. I see no reason not to believe the manufactorers...

I have this bridge for sale...

John Smith wrote:
Eric Greenwell wrote:

Do you have a reference to the regulation concerning power
requirement? I haven't been able to find it, and people just seem to
rely on the product descriptions when I ask about it.

Actually, I do, too. I see no reason not to believe the manufactorers.
According to Funkwerk, output requirements are higher for tansponders
which are operated in aircraft flying at altitudes above 15,000ft or
speeds above 175kt. Unfortuately (of fortunately), gliders often operate
higher than 15,000ft.

My problem is the manufacturers do not specifically say their 250W
transponders are required by the FAA, in gliders, above 15,000'. They
often refer to EASA or other regulations that just hint at it, or make
non-specific remarks that may apply only to certified airplanes. It
looks like Darryl has found what I want, however.

I write this with the European situation in mind where Mode S is already
mandatory. As air traffic is typically an international thing, I would
assume that the FAA and EASA have been reasonable enough to discuss this
and to agree to the same requirements.

And they probably have, for international operations, but for gliders in
just the USA? Or in a wave window? We should not assume anything about
in-country requirements, because regulations do vary. Note that Europe
is going to Mode S and 8.33 radio channel spacing; the USA is not.

BTW, problably not the cheapest but one of the more popular mode S
transponders in Europe is the TRT800H by Funkwerk.
http://www.funkwerk-avionics.com/cms...4&changelang=4

I know there are many choices in Europe for Mode S, but I am aware of
only two brands sold in the USA that have units suitable for gliders:
Becker and Garrecht. The least costly is still $600 more than a Mode C unit.

If the Mode S units had a significantly lower power requirement, they
might be worth the extra money. Comparing the datasheets of the Becker
models, both the standby and operating drains seem similar. Perhaps I am
misinterpreting the figures.

The Garrecht unit seems to promise a worthwhile reduction in drain, in
part because it does not require an external encoder. It costs almost
$1000 more than a Becker + encoder, however.

Perhaps some enterprising soaring supply company should buy a lot of
those unusable Mode C transponders from Europe and offer them for sale
to USA customers at attractive prices.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly

* Updated! "Transponders in Sailplanes" http://tinyurl.com/y739x4
* New Jan '08 - sections on Mode S, TPAS, ADS-B, Flarm, more

* "A Guide to Self-launching Sailplane Operation" at www.motorglider.org

On Jan 8, 12:01*pm, Itsaplane wrote:
Needing a replacment, my transponder shop told me that above 15k' the
FAR's require a 250 watt transponder (125w below 15k').

True?

I'm pretty sure that sailplane owners are mostly installing 175 watt
units and flying them to 18k' (and higher in wave windows). *Right?

If this 15k' rule is real, I'm supposing that, since gliders aren't
required to have a transponder except in certain airspace (this
airspace is all below 15k' -- except Class A...) that we're generally
free to install anything we want (except 18k' in Class A?).

Bottom line -- 175 watts or 250 watts?

Eric Rupp
ER
(My Terra TR250D transponder is inop and I'm having trouble getting
parts - anybody have a dead one that we might be able to salvage from?)

Eric,

I don't believe that is true. I think that is from the specifications
from the Becker transponders. The Microair T2000 is 200w and specs
say 62,000 feet.


http://www.craggyaero.com/microair.htm

Richard
www.craggyaero.com

On Jan 8, 12:21*pm, Richard wrote:
On Jan 8, 12:01*pm, Itsaplane wrote:



Needing a replacment, my transponder shop told me that above 15k' the
FAR's require a 250 watt transponder (125w below 15k').

True?

I'm pretty sure that sailplane owners are mostly installing 175 watt
units and flying them to 18k' (and higher in wave windows). *Right?

If this 15k' rule is real, I'm supposing that, since gliders aren't
required to have a transponder except in certain airspace (this
airspace is all below 15k' -- except Class A...) that we're generally
free to install anything we want (except 18k' in Class A?).

Bottom line -- 175 watts or 250 watts?

Eric Rupp
ER
(My Terra TR250D transponder is inop and I'm having trouble getting
parts - anybody have a dead one that we might be able to salvage from?)

Eric,

I don't believe that is true. *I think that is from the specifications
from the Becker transponders. * The Microair T2000 *is 200w and specs
say 62,000 feet.

http://www.craggyaero.com/microair.htm

Richardwww.craggyaero.com

Yes it's true, but it's also not...

The above/below 15,000' comes from TSO-C74c see
http://www.airweb.faa.gov/Regulatory...9?OpenDocument

See other specifications there to explain the differences, but for
power output the TSO requirments are

---QUOTE---

2.11 Transmitter Power Output.

a. For equipment intended for installation in aircraft which operate
at altitudes above 15,000 feet, the peak pulse power available at the
antenna end of the transmission line of the transponder must be at
least 21 db and not more than 27db above 1 watt at any reply rate up
to 1,200 per second for a 15-pulse coded reply.

b. For equipment intended for installation in aircraft which operate
at altitudes not exceeding 15,000 feet, the peak pulse power available
at the antenna end of the transmission line of the transponder must be
at least 18.5db and not more than 27db above 1 watt at any reply rate
up to 1,200 per second for a 15-pulse coded reply.

c. The standards of this section assume a transmission line loss of
3db and an antenna performance equivalent to that of a simple quarter
wave antenna. In the event that these assumed conditions do not apply,
the equipment must be adjusted as necessary to provide a transmitter
power output equivalent to that specified.
---END QUOTE---

But how to interpret this? The way I read these TSO requirements are -

below 15k feet 18.5dbW to 27dBW = 70.8W to 501W power at coax output
at the antenna
above 15k feet 21dbW to 27dBW = 126W to 501W power at coax output at
the antenna

below 15k feet 18.5dbW+3dB to 27dBW+3dB = 141W to 1kW power at
transponder output
above 15k feet 21dbW+3dB to 27dBW+3dB = 251W to 1kW power at
transponder output

Where I have assumed the 3dB cable loss in part(c).

I'm not aware of any requirement for what power output manufactures
are required to quote. Are they talking about the power output at the
transponder or the TSO-C74c specified power at the antenna input with
assumed 3dB cable loss? I suspect manufactures normally want to quote
the biggest power output they can however in the case of Microair I
assume they are talking about 200W at the antenna coupling since they
would not meet the ~250W requirement. Maybe one of their dealers can
clarify this. (and yes technically as well there is ambiguity about
peak vs. other power measurements, but again I'd assume manufactures
are going to quote peak to maximize the number and since that is also
what the TSO talks about).

Anybody got a different interpretation of the TSO?


Darryl