Flarm in the US

On Aug 11, 11:55*am, Westbender wrote:
On Aug 11, 10:41*am, Dave Nadler wrote:



On Aug 11, 11:27*am, Westbender wrote:

On Aug 11, 10:09*am, mattm wrote:

On Aug 11, 10:41*am, Westbender wrote:

Forgive me if this is a really dumb question. I don't know much about
transponder operation.

Is it a technical requirement for a transponder to only transmit when
it's been interrogated by a ping from a remote source? I'm just
wondering why transponders can't have a "timeout" mechanism built into
it where it will automatically report/transmit if it hasn't been
pinged in a certain amount of time. Something like a 30 second
timeout? Maybe user-selectable? For the folks who fly in remote areas,
wouldn't something like this help? Or is the transponder response of
no use without pairing it with a request (ping)?

That's the meaning of "transponder" -- it transmits a response (to a
radar paint), plus it includes additional information. *It goes back
to
WWII days when it was originally known as IFF -- Identify Friend or
Foe. *The detection methods based on transponder response depend
on the timing between when the primary pulse is seen and the response.
The larger the duration, the further from the transponder you are.

This is the point of the FLARM scheme -- all the units periodically
broadcast their status, so they are visible even when there is no
radar around.

-- Matt

When I read the "how it works" on the Zaon website, it says it reads
the response. It doesn't say anything about using the primary pulse in
it's process. Is that typical of PCAS systems?

This is where my question originates. It seems that the PCAS system
might not need the initial request from a radar to evaluate threats.
If so, then wouldn't an aircraft transponder "replying" without a
radar pulse give surrounding aircraft with PCAS the means to detect?

A PCAS system replies on someone else interrogating the
transponders. "Someone" is either a ground radar station or
a TCAS-II equipped aircraft. If you are in a valley without
radar and without overflying jets, you will hear nothing.

Hope that helps,
Best Regards, Dave- Hide quoted text -

- Show quoted text -

Right, did you read my first post?

Since the MRX PCAS (passive) only uses the reply from transponders,
wouldn't it be nice if the trig had a timed/scheduled transmit when
not interrogated for a certain amount of time? If so, a combination of
a trig/PCAS would be relatively inexpensive for glider-to-glider
detection (yeah, yeah, assuming everyone had that combo). The best
part would be the benefits of the "normal" operating mode of the trig
and PCAS in relation to other GA and commercial aircraft.

What are the ramifications of doing something such a thing?

You CANNOT do that.
You will never get approval for transmissions on 1090...

Hope that's clear,
Best Regards, Dave