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Re: Expected noise results with Drake converter (no satellite.)



Hi Guys,
Just a note, the offset fed dishes have to be tilted "down" by 21.5
degrees so that might have some thing to do with the poor performance.
The DSS dish when properly fed should outperform the BBQ.
Tony AA2TX

---
At 06:33 PM 5/23/01 -0400, barrie@perth.igs.net wrote:
>Ed
>
>Don't give up on the DSS dish. I followed your advice and had mine working
>on this morning's pass. Copied the Beacon and I8CVS at MA 106  Range 59 K. I
>haven't got any numbers but it doesn't perform as well as the BBQ.

...

>Oh yes! I did note I had to lower the elevation by a few degrees from what I
>thought was the same elevation I was using on the BBQ.
>
>
>Thanks for your advice  73 Barrie VE3BSB
>
>----- Original Message -----
>From: "Edward R. Cole" <al7eb@ptialaska.net>
>To: <amsat-bb@AMSAT.Org>
>Sent: Sunday, May 20, 2001 6:25 AM
>Subject: Re: [amsat-bb] Expected noise results with Drake converter (no
>satellite.)
>
>
> > Al and Hasan,
> >
> > Eary this morning, after trying my 18 inch DSS RCA dish/5-turn Helix/Drake
> > [435 MHz IF...xtal changes only], 50-foot Rg-213 [2.5 dB loss], to a
> > FT-736R [a freind's], I have to report total failure to hear the beacon!
>I
> > then subtituted a BBQ style dish with 21 dB gain and dipole feed, and
>could
> > just detect the beacon about 1-2 dB above noise.  This at about 63,000 km
> > and squint ~6 degrees.  This is not quite the expected and estimated 7 to
>9
> > dB S/N!!!
> >
> > Not sure what the problem with the offset dish/helix is: pointing
>probably,
> > feed adjustment, bad feed [swr?], not enough antenna gain, too high NF,
>not
> > the expected IF gain from the Drake, ...?  All the above?
> >
> > I was visiting the qth of my freind Mike, WL7BQM, and his Meyers dish [~24
> > dB] dipole combo, Conifer preamp [NF?], Rg-6 coax, FT-736R is doing
> > fantastically well.  We heard the beacon from 25 to 35 dB above the noise.
> > He has 100% copy on the TLM with ao40Rcv.  We had fun working a few
>stations.
> >
> > So folks, there is theory and there is reality.
> >
> > I'm back to the "drawing board" and the bench.  Waiting for my Kuhne
> > preamp.  Looking at setting up a 4-foot dish.  Wondering why the little
> > dish performed over 35 dB down from Mike's system?  As they say...stay
> > tuned for future developments.
> >
> > Ed
> > Al, with no satellite you should see a significant rise in Rx noise when
> > you turn on the preamp.  I see about two s-units; some see up to S-9!
> >
> > >
>
>----
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----
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