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Re: AO-40 heard on 2.4GHz in VK




Hi John, et al,
>

>For those of us in the "gearing up" stage of development, it would be
>interesting and informative if you included what equipment you are using.
>How big is that dish (or dipole!!), what feedline and length, downconverter
>brand.
>
In the interest of saving bandwidth I have not been in the habit of
including my "brag-file" on this medium :-)

The "S" band setup here is pretty much the same as when I put it together
for AO-13 and Arsene. I have a 1.6 metre ground mounted dish which is
manually pointed. This is good enough for Goverment work and certainly
adequate for apogee operations. It has a G3RUH feed at the prime focus. The
feed consists of a 2.25 turn left hand helix made from 1/8" refrigeration
capillary tube and using a 1/4" wide, 1/4 turn matching gizmo (sorry ...
that's a technical term) soldered to the first quarter turn of the helix.
This first quarter turn is almost parallel with the ground plane and gives a
close match to 50 ohms. The gizmo is cut from shim brass. The ground plane /
mount is cut from an old jam tin and is about 4 1/4" diameter with 1" of the
side of the tin left on to form a "choke". I've used this design with great
success on 1.2 GHz, 1.7 GHz (wxsats) and on "S" band.

The pre-amp is from DEM and mounts directly at the helix with just an "N"
type adaptor in circuit. From there I feed with approx. 50ft of good co-ax
to the DEM downconverter which I keep in the shack to minimise frequency
drift.

In other words it's a pretty standard no-corners-cut outfit. I can receive
6 - 8 dB of sun-noise (on a good clear summer's day :-) and the signals from
the ao-40 beacon are 6 - 7 "S" units above my noise floor. This is
consistent with the result from AO-13 and (albeit briefly) from Arsene.
Using the rx "S" meter, the sun-noise tests yielded, in CW mode,
noise-floor=s4, sun=s5.2 and in FM mode, noise-floor=s6.5, sun=s9+15dB.
Those are my recorded 'fire-up' tests. I have noticed slightly better
figures on some occasions since that time. I don't want to act the guru
here. My setup is very much homegrown and I have never had access to fancy
test gear. I'm a Mechanical Engineer and ham radio is a hobby only.

My best regards to all grappling with the complexities of "S" band and
looking forward to contacting you all on mode LS, definitely the mode of the
future.

Best wishes to all on the list for 2001 and special thanks to the ao-40
command team for their tireless efforts. I know one of the team personally
(Graham vk5agr) and I know how hard they work.

Bill Magnusson ... vk3jt
Milawa
Australia.


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