ATC Radar Question

Jackie wrote:
Clark wrote:
Jackie wrote in
:
[snip]
Does precision approach radar require a transponder to report altitude?

PAR uses a height finder radar to provide sufficient vertical
resolution for precision approaches.

Could you elaborate on how the "height finder" works?

the elevation radar determines altitude the same way the azimuth radar
determines bearing.

"Bob Noel" wrote

the elevation radar determines altitude the same way the azimuth radar
determines bearing.

There are actually two radars running for PAR, right? One sweeping left to
right and one sweeping up and down, I think.
--
Jim in NC

"Clark" wrote in message
...
"Morgans" wrote in :


"Bob Noel" wrote

the elevation radar determines altitude the same way the azimuth radar
determines bearing.

There are actually two radars running for PAR, right? One sweeping left
to right and one sweeping up and down, I think.


As far as I know you are entirely correct. The installations I've seen
(years
ago and far away) have two independent radar systems, one for the
horizontal
and one for the vertical. Of course I've only seen ancient technology and
I'm
sure that these days it could be done with one steerable beam.

Older PARs (which there are many still around) don't really have two
independent systems. They basically separate the radar signal between two
antenna (one for azimuth and one for elevation). Newer designs (which are
still quite old) use a phase array which steers the beam. In both designs
the transponder is neither required or used.