Eric what are you reading in the manual that says 0.4 nm? The only
reference I saw to 0.4 nm is the discusison that if you see false
targets of less than 0.4 nm range then you may need to clean the
transponder antenna, etc.

Also it is worth remembering the Zaon PCAs devices are not just
"blanking" the receiver during the local transponder reply. The Zaons
are reading and doing an altitude decode of the local transponder
signal and using that if possible for the altitude reference rather
than the built in altimeter. How good their RF front end and post RF
digital processing is will determine how well they can differentiate
partially overlapping pulse trains from the local and other
transponders. And you better believe they have to do this since the
most nieve approach of "blanking" during the entire ~20us transponder
pulse train (ignoring the ident pulse) would give a dead zone of
~6km. I'd love to see a schematic.. :-)

Like other posters I suspect this not much of an issue in practice
because of multipe illuminations from SSR, TCAS etc. However one thing
with some of the funkier glider tranponder antenna installs is that
the PCAS may be seeing much more RF power from the local transponder
than the designer expected, especially for situations like with RF
transparent fiberglass fueslages and maybe a less than great ground
plane betwen the PCAS and antenna, tranponder antennas mounted in the
cockpit etc. In which case maybe the dead zone is larger because of
the Zaon's reduced ability to detect overlapping pulse trains.

---

The Zaon MRX works amazingly well in my experience and is a great
suppliment for transponders in gliders, but especially for seperation
from heavy iron lets keep the focus on getting transponders in gliders
in heavy traffic areas. Transponders absolutely work -- with no effort
from me except turning on my transponder I often notice traffic
vectored around my glider when flying near Reno (I hear Reno arivals/
departures telling traffic I'm there).

Darryl

On Mar 10, 8:29 am, Eric Greenwell wrote:
jcarlyle wrote:
The key lies in how they blank the receiver. Since there is no
connection to your own transponder, I think they simply blank for time
X when they get a signal of over Y watts. If they do, that will
produce the situation I described above.

Multiple radars will change the situation, but I believe there will be
blind spots there, too. I think you'll have multiple blind cylinders,
each pointing at the various radar sources.

As long as they don't overlap, then maybe the unit can still pick out a
potential threat.



And you're correct, it isn't what Zaon shows in the manual. It would
definitely be best to talk with them directly about happens in this
situation.

Eroc, I know I won't get any time this week to call them. Could you do
it, and post the results?

Sure, I'll try to contact them Monday.



-John

On Mar 10, 10:24 am, Eric Greenwell wrote:
This seems like a plausible analysis, but it's not what Zaon shows in
their manual; instead, they talk about a "bubble of detection" around
your aircraft. A query to Zaon should be the next step, as it might get
an explanation of how their units deal with this situation.

There is a situation that elimanates this problem: multiple radars. This
could be a TCAS equipped airplane or another ATC ground radar.

--
Eric Greenwell - Washington State, USA
* Change "netto" to "net" to email me directly
* "Transponders in Sailplanes"http://tinyurl.com/y739x4
* "A Guide to Self-launching Sailplane Operation" atwww.motorglider.org