Thanks to James for the advices and to Jerry and Jim for the news.

Jerry: I'd like to know more about your solution, if you agree.

Jim Lux ha scritto:
There's a set of articles in IEEE Antennas and Propagation Magazine (not
the transactions) a few years back that has all the equations and design
rules for all of the various reflector configurations.

Where I can find these articles?


Best wishes,

Emanuele Colucci

"Emanuele Colucci" wrote in message
...
Thanks to James for the advices and to Jerry and Jim for the news.

Jerry: I'd like to know more about your solution, if you agree.

Jim Lux ha scritto:
There's a set of articles in IEEE Antennas and Propagation Magazine (not
the transactions) a few years back that has all the equations and design
rules for all of the various reflector configurations.

Where I can find these articles?


Best wishes,

Emanuele Colucci


Hi Emanuele

I submit that, if you intend to actually build an antenna for L-Band and
are restricting its diameter to 3 meters, you need not consider a cassegrain
feed. The reflector at the focus is too small to allow the primary feed to
illuminate it with a high percentage of the available source at the rear of
the dish.

For one example, let the cassegrain reflector be 1/2 meter diameter and be
spaced 1meter from the apex of the dish. Wouldnt that suggest that the
primary beam, from behind the dish will have a beamwidth of about 30 degrees
(at -3dB)??
If the cassegrain reflector is made bigger, that blocks more of the
parabolic dish apperature. If the cassegrain reflector is made smaller,
that increases the need for a high gain primary feed.

It is my contention that, if you want to research Cassegrain antennas,
that is a worthy project. If you want to build a functing L-Band telescope
with 3 meter dishes, dont include cassegrain feeds in the project.

Jerry KD6JDJ

Emanuele Colucci wrote:
Thanks to James for the advices and to Jerry and Jim for the news.

Jerry: I'd like to know more about your solution, if you agree.

Jim Lux ha scritto:
There's a set of articles in IEEE Antennas and Propagation Magazine
(not the transactions) a few years back that has all the equations and
design rules for all of the various reflector configurations.

Where I can find these articles?


Best wishes,

Emanuele Colucci



You might want to take a look at W1GHZ's online book
http://www.w1ghz.org/antbook/conf/Mu...r_antennas.pdf

He gives a procedure, and refers to a variety of sources, among them,
the ones I was thinking of:
The articles I was thinking of were by Christophe Granet at CSIRO in
Australia, and published in Tom Milligan's "Antenna Designer's Notebook"
column in the A&P Magazine

April 1998, "Designing Axially Symmetric Cassegrain or Gregorian
Dual-Reflector Antennas from Combinations of Prescribed Geometric
Parameters"

June 98, Minimum blockage
Dec 99, Displaced axis dual reflector antenans (4 types)
Dec 2001, Dragonian Dual-Reflector
June2002, Offset Cassegrain or Gregorian
Dec 2003, Designing ..offset.. Part 2, Feed-horn Blockage Conditions.

There's some FORTRAN available too, from Tom Milligan.