Re: [amsat-bb] TransSystem AIDC 3733 w/built-in dipole?

["Gary \"Joe\" Mayfield" <gary_mayfield@xxxxxxxxxxx>]

Jon,

     I have been using the 3733 with integrated antenna and dish for some
time.  It works great!  I seem to hear at least as well as everyone else
(there are a few exceptions who's superior, and considerably more expensive,
equipment I humbly bow to).  I cannot compare to covering the dish with
screen and running a helix feed, because I have never done that.

A few lessons from experience.

1.  It is absolutely necessary to do the stub cut mod.  You probably won't
hear the bird without it.  I made lots of contacts on the S2 downlink using
a 3733 with only this mod.

2.  It is a good idea to do the bandpass filter mod.  It will should yield
close to a 3dB improvement.  My biggest lesson learned from this is just how
small a change 3 dB is!  It is detectable, but only barely.

3.  Using the original feed and reflector leaves a very clean installation.
Very little of the dish is obscured by the downconverter and feed.  It is
also fairly robust, i.e. weather resistant.  I live in South Dakota this is
important to me.

4.  The theoretical maximum improvement from changing the feed, and covering
the dish would be another 3dB.  In reality this is impossible to achieve.
2dB of improvement would be a good figure to shoot for.  Some of the
possible gottchas follow:  You will need to match your feed to the
downconverter.  You are introducing either feedline or connectors at 2400
MHz where they can hurt you the most.  Your feed will either illuminate
beyond the edges of the narrow axis of the dish or only illuminate a portion
of the long axis of the dish (i.e. the dish is not round).

    These are my conclusions.  Your results may be different than mine.  I
know there are a lot of folks out there better at this stuff than I am.

73 and Hope to Hear you ON AO-40,
Joe
ka0yos@amsat.org



----- Original Message -----
From: "Jon Neher" <jneher@darkwing.uoregon.edu>
To: <amsat-bb@AMSAT.Org>
Sent: Wednesday, August 15, 2001 6:18 PM
Subject: [amsat-bb] TransSystem AIDC 3733 w/built-in dipole?


>
> Does anyone have any experience using the 3733 with it's
> built-in dipole and a BBQ dish?  Is it usable with AO-40?
> How does it compare with a 3733 and a helix feed and a screened BBQ dish?
>
> Thanks for any info anyone may have.
>
> Thanks,
>
> Jon
>
> Computing Center Internet: jneher@darkwing.uoregon.edu
> University of Oregon Voice: (541) 346-1731
> Eugene, OR 97403-1212 WWW http://darkwing.uoregon.edu/~jneher
> Amateur Radio: N7WNX
>
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