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RE: AIDC 3033 3' BBQ Dish



Hello Bob

> Wow, now that I finally found some time to start working on my Sband
> receive, I went to all the 31 emails I saved on the subject of AIDC
> downconverters, and find that all of them have to do with the model 3733
> and yet I have the 3033.  What is the difference?

A 3033 has a nominal gain of 30dB whereas the 3733 has 37dB. Either way
should be plenty! If you haven't already, you will want to snip the 1/4 wave
stub inside first as per
http://members.aol.com/k5gna/AIDC3733modifications.pdf and even better
perform the filter mod too.

> Also, K5OE's article in the amsat symposium says the focal length is 15.5
> inches for the AIDC feed, but the above two emails and my own 3033 are
> much shorter.  My 3033 can be mounted as short as 11 inches and as long as
> 12.75 inches from the dish.  But nothing close to 15.5?

The focal length is a function of the dish not the feed. If you know the
focal length to be between 11 and 12.75 inches then place it there. 15.5"
probably refers to a different dish. As a general rule a simple
dipole/reflector configuration has its phase center between the dipole and
reflector. You want to put the phase center of the feed at the focal point
of the dish. Don't worry +/- 1" or so to begin with. Correct this by trial
and error when you hear the beacon. You may well not notice much difference
at 2.4GHz.

All the feed has to do is to illuminate the dish in the most efficient
manner possible, attempting to make the feed's 10dB beamwidth (there's also
a good case for using 13 or 15dB beamwidth instead) to the angle subtended
by the dish from the feed.

As a general rule get the focal point correct first and worry about
beamwidths and illumination angles when you're at a loose end.

Does this mean the first transatlantic car park to parking lot AO-40 QSO is
on the cards? (http://www.g6lvb.com/images/parkinglot2.jpg - Tnx K5OE,
KC2HAX)

73 Howard G6LVB

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