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Re: AO-40 Reception



Just ran the standard BBQ dish, DEM ULNA13 > barely modified
Drake 2880 (Millicom 251) > TS790A > AO40RCV on today's AO40 AM
NA pass. The results were 100% CRC good MB copy at all ranges except
for when  poor squint and small antenna footprint near the perigee caused
fades just a bit too deep. Virtually all of the passband QSO's were good
copy.

Total cost to upgrade to fairly solid S-band receive was under $250.

This setup will not copy horizon to horizon but it seems like it will be
adequate
to work the more favorable squints. It is obvious even at this early stage
that
close attention must be paid to AO40's antenna pattern and the squint angle
when deciding on which pass to work. Within it's limitations I would say that
it
will be a good starting point.

It is essential to have a simple signal source and a good program to predict
when and
where the SAT is. Try not to pick times when the doppler is shifting fast. For
me
the ranges of 24-35km seem to be the easiest to acquire. Rotors are not needed
for just a system checkout but knowing pointing direction to within about 5
degrees
is an absolute must for the BBQ dish. I have my dish with the long axis
horizontal.
This allows for less stringent elevation positioning. A tweak of just a few
degrees
in azmuth makes a big change in signal strength.

The answer is yes, it will work!
Thanks to everyone that posted hints and encouragement on the BB.
Now to the tower, and the 70cm uplink!

Vince Risalvato
KD7AI




----- Original Message -----
From: "Frederick M. Spinner" <fspinner@hotmail.com>
To: <amsat-bb@AMSAT.Org>
Sent: Saturday, May 12, 2001 7:48 PM
Subject: Re: [amsat-bb] AO-40 Reception


>
> Has anyone else out there used a Drake with an outboard preamp--
> I did all the mods that don't require spending $$$ on the Drake
> so far (not the MGA MMIC, Toko Filter)-- which supposedly puts the thing in
> the 6dB ballpark (I'll find out at Dayton I suppose).. I have an old DEM
> 2400 MHz (LUA) preamp, measured at CSVHF 2000 to have 11.8 dB gain, and a
> 0.82 dB NF.
>
> Interestingly enough, the Drake behind that preamp seems more sensitive than
> the OLD DEM downconverter behind the same preamp.
> Which is wierd as the DEM converter should have the same to nominally
> less NF.. (It does have less conversion gain, though)...
>
> I guess I'll need to pick up one of those transystems at Dayton and
> try it out..
>
> Fred W0FMS
snip....

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