Transponder Praise

Eric, I wasn't too impressed with the antenna extenders that Zaon
offers. They use RG-174 cable, and while it's OK for short runs it
would markedly decrease the signal strength running from my tail cone
to my instrument panel. I've found several places on line that offer 6
meter male to female RP SMA cables made from LMR 200 for less than
$15. The attenuation with LMR 200 at 1 GHz is 10 dB per 100 feet,
rather than the 22 dB per 100 feet with RG-174.

I guess there's a possibility that high interrogation rates could mess
up the Zaon range estimate, but even here in the PHL NY area the
transponder's transmitting triangle only flashes about once a second.
Could be that there are many, many transmissions per flash, but I've
noticed that generally if the Zaon says the range is within 3 miles of
me it is pretty accurate (to my "calibrated" eye, that is).

-John

On Jul 7, 2:39 pm, Eric Greenwell wrote:
Shadowing is certainly a possibility. I've also wondered if the amount
of radar interrogations can cause the same thing; e.g., where I fly in
SE Washington state, my transponder is triggered only 5-10 times a minute.

Rather than just relocating the antenna, you can get Zaon's dual antenna
option. That puts antennas top and bottom on the aircraft, essentially
eliminating all shadowing. It might be easier than moving one antenna to
the tail, but it's pricey at $280 for the option, plus two blade antennas.

--
Eric Greenwell - Washington State, USA

jcarlyle wrote:
Eric, I wasn't too impressed with the antenna extenders that Zaon
offers. They use RG-174 cable, and while it's OK for short runs it
would markedly decrease the signal strength running from my tail cone
to my instrument panel. I've found several places on line that offer 6
meter male to female RP SMA cables made from LMR 200 for less than
$15. The attenuation with LMR 200 at 1 GHz is 10 dB per 100 feet,
rather than the 22 dB per 100 feet with RG-174.

The PCAS MRX Dual Antenna Harness isn't really an "extender", but a way
of improving coverage to eliminate blind spots. I believe the antennas
used with the extender could be mounted close to the cockpit: e.g., one
on top of the glare shield, and one below it on the outside of the
glider (you couldn't do that on a glider that uses a CG hook to tow
with, of course).

Those locations would allow very short cables, if you wanted to;
however, the fact that two antennas are used probably makes up for
losses in the cable. If my math is right, the 15 foot cables they supply
do cut the signal from each antenna by one half, so that suggests they
intend the total signal (both antennas) to be the same as the one
antenna mounted directly on the unit. In any case, the dual antenna
package and the PCAS MRX Single Antenna Harness include "gain adapters",
so perhaps concerns about signal loss are irrelevant.

I suggest calling tech support at Zaon about the cable to use for a
remote mounting. Proper operation might require these losses, which
could be accounted for by the gain adapter.


I guess there's a possibility that high interrogation rates could mess
up the Zaon range estimate, but even here in the PHL NY area the
transponder's transmitting triangle only flashes about once a second.
Could be that there are many, many transmissions per flash, but I've
noticed that generally if the Zaon says the range is within 3 miles of
me it is pretty accurate (to my "calibrated" eye, that is).

Actually, I was thinking infrequent interrogations might be the problem,
but it was just a guess.

--
Eric Greenwell - Washington State, USA
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