Hi to everyone and thanks for answering to my message.

Richard Clark ha scritto:
Hi Emanuele,

This is probably due to the way the question was offered. You want a
complete solution to an unknown problem.

You and Dave were right. I originally posted the message in the homebrew
newsgroup because I was looking for a complete guide to design a cas in
order to build a little radiometer working in the "water hole" (1420 ~
1640 MHz) for an hobbystic aim.
The book I used at university to study antennas - Antennas and Radiowave
Propagation [by Robert E. Collin] - simply doesn't cover in depth this
argument. It just cites the Cassegrain feed system as an alternative to
prime focus paraboloidal reflector antennas, because the cassegrain feed
does't receive the thermal noise from the ground.

I was looking for a complete resource to study the system, and this is
why I wrote he to find someone with good advices.

Now, the thing I have now understood is that I haven't to be so
synthetic while writing a message.

So, I would like to study (and eventually build) a radiometer who
listens to 1420 ~ 1640 MHz, with a passing bandwidth of 8 MHz, in order
to receive a minumum density flux of 240-260 Jy (a Jansky is 10^-26 W /
[m^2 * Hz]). I need low antenna temperature (but not as cryogenics ones!).


5. Budget (time and/or money);

I can't answer this question yet. Surely, I haven't more than 5-600
euros to spend in the building/buying of the antenna.

6. Specific issues (phase control?);

Nothing special: I would like an output signal proportional to the power
of the radiation picked up.

7. Application issues (EME?).

Amateur radioastronomy.

Well, that's all by the moment.

Greetings,

Emanuele Colucci