Dish types

Q

QWEREWQ

ASBO Club Member - Persona non grata
My Satellite Setup
TWINHAN-USB-NO CI-CORE2DUO-4GB RAM
My Location
Egypt
i know whats prime focus and whats offset/dual offset...
but what the heck is a cassegrain dish ?!!
 
QWEREWQ said:
i know whats prime focus and whats offset/dual offset...
but what the heck is a cassegrain dish ?!!
Click to expand...
Ask google for cassegrain. But what is dual offset you know?
 
simply dual offset has a small offset in place of lnb holder to increase the gain by ~10-20%
while i was searching for a pic i luckly foud out whats cassegrain!:-snipe
attachment.php

the gregorian is the dual-offset,while the the cassegrain turned out to be the same idea of dual offset but for prime focus :cool:
real examples...
90cm-visiosat_big.gif
this one is better
visiosat-120-grego_big.gif
 
Since an offset dish is only a section of a full parabolic shape, the cassegrain is actually the forerunner of the Gregorian.

What distinguishes the two in terms of design is the secondary reflectors, the Cassegrain being (mostly) convex, and the Gregorian always concave.

_http://en.wikipedia.org/wiki/File:Parabolic_antenna_types2.svg

As before, there are advantages of one over the other in terms of environment/ease of manufacture/cost.
 
i think there is one simple advantage that matters...
size/weight/area over signal gain however the setup is more complicated than regular dishes...
 
For a supposed beginner you know an awful lot about obscure stuff to do with the satellite hobby!
 
Analoguesat said:
For a supposed beginner you know an awful lot about obscure stuff to do with the satellite hobby!
Click to expand...
Well that's because i searched a lot about lots of things !
Yet I am still a newbie because i haven't installed or dealt with these stuff physically.(I only have static information)
I knew from the start that there a second reflector on the 4.8 M dish i saw on PDF file,but i didn't know that cassegrain refers to the sec. reflector.
_____________________________________________________________________________________________________________________________
Is it true that loading frame could be used to mount 4.8M dish on a roof top ?!
which has better gain cassegrain or gregorian?
For C/Ku Feed should i use bandpass for each band?must i use OMT?

Thanks
 
QWEREWQ said:
...while i was searching for a pic i luckly foud out whats cassegrain!:-snipe
Click to expand...

Please do not post IMG as per the rules. The forum staff here would appreciate you editing your post and upload the images as attachments to our server.
 
QWEREWQ said:
the gregorian is the dual-offset,while the the cassegrain turned out to be the same idea of dual offset but for prime focus
Click to expand...
That's not true. Both Cassegrain and Gregorian designs can have the secondary reflector on axis, or mounted asymmetrical. The most notable difference between the two is that a Gregorian produces an image that is oriented the same as the source, whereas the Cassegrain produces an image that is rotated 180º in relation to the source.
 
Huevos said:
That's not true. Both Cassegrain and Gregorian designs can have the secondary reflector on axis, or mounted asymmetrical. The most notable difference between the two is that a Gregorian produces an image that is oriented the same as the source, whereas the Cassegrain produces an image that is rotated 180º in relation to the source.
Click to expand...
Yes i noticed after a wider search.
 
is it possible to assemble a c/ku feed without a polarizor?
 
Back
Top