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RE: Looking for AO-40



Dave, I am using a Spectrum Analyser in a similar way to you to monitor
the Beacon strength, particularly to check the signal to noise ratio. It
is difficult to find even when its 10dB out of the noise.
Make sure that the analyser noise line increases when you connect to the
converter. The Transystem unit should drive the line up about 5dB - unless
you have a very long run of coax - with the NorSat I need an additional 10dB
between it and the analyser. (I use an old 2-M pre-amp.)
I am now seeing the MB 20+dB above the noise in the analyser (Cushman CE-15)
on narrow width - uses a <3kHz IF filter. The noise output of the converter
is currently registering -108dB in the analyser. (Typical figures
Noise=-111dBm
and the Beacon=-90dBm into the analyser.)

  System = 600mm Dish >> 13ULNA >> Drake >>>>>>>>>>>> Cushman.
(With this set-up I measured >1.5dB rise when swing the dish through the
Sun.)

Without the 13ULNA I get -115dBm on the 10Khz scan setting.

When you tune for the beacon look between 145.290 and 145.360 - it can be
more than 30kHz off frequency due to drift and Doppler.

Provided your 3733 lifts the analyser trace off the bottom (you may need max
sensitivity) I would expected you should be able to see the Beacon about
10-15 dB out of the noise - narrow bandwidth - short scan width.

Best of luck with your hunting.

73, Terry,  ZL3QL.
-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Dave Bourne
Sent: Wednesday, 5 September 2001 11:15 AM
To: amsat-bb@AMSAT.Org
Subject: [amsat-bb] Looking for AO-40


	I received my 3733 downconverter from K5GNA (with all mods) on Saturday and
have not been successful in hearing AO-40. I tried using my Conifer dish on
Saturday Evening using the Conifer feed and nothing. On Sunday Evening I
tried again using a 36" offset feed DBS type dish along the 3733 "dipole"
feed and again nothing. I have a Spectrum Analyzer (HP 8558) and I see
nothing when tuned to 144 Mhz looking at the output of the downconverter
through the power divider. When I pan my antenna towards LA (I live in
Southern CA) and tune up in frequency on the Analyzer I can see some
"Wireless Cable" digital carriers coming through the downconverter. If I
disconnect the downconverter from the analyzer the noise floor drops about 8
to 10 db so I believe that the downconverter is working. I use Nova tracking
software and it seems to work OK so I believe that I'm pointed in the right
direction at the right time with my antenna.

1. What type of modulation is used on the Beacon.? Should I see anything on
the Analyzer ?

2. On what frequency should I see the Beacon on (after downconversion) ? Is
it something like 144.350 ?


Thanks

Dave Bourne WB8TMP
Corona, CA

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