Date:   Mon, 03 May 2004
From:   David Perry
To:     Andre Phillips
Subject:  SC APT receiver

Hello,

You mentioned on your website that you'd be interested in hearing from
anyone who had built the weather satellite receiver featured in SC
magazine earlier this year. Here I am...

I've been trying to pick up these signals for some time, mainly by
trying to build a downconverter. I wasn't having much luck so I jumped
at the DSE kit when it became available.

It was straight forward to assemble. Few coils to wind, bit of SMD
soldering. Tuning was a bit of a hassle. I don't own a 150MHz frequency
counter/generator. Few people do. I tried tuning it by ear during
passes, without luck.

Today I took the receiver into uni, and made use of the considerable
resources of the Electrical Engineering Department of the University of
Melbourne. I'm an undergrad there. Within 15 minutes I had it tuned
using an RF signal generator and spectrum analyser.

The reason I couldn't find the signals was that the local oscillator in
the receiver couldn't be made to reach a high enough frequency, the
trimpots ran to their stops before getting near. This was solved by
pulling apart the turns of coil L2. I was then able to tune the receiver
up to 137.5/137.62MHz.

I tried it an hour ago with NOAA 15, and I received a strong signal. A
noisy one, but when the satellite was near overhead, I was able to get a
decent picture with clouds stretching south of Tasmania visible. This
was without the use of the pre-amp in the kit which I've yet to try.

I was using a Quadrafilar Helix antenna that I built a couple of years
ago. It's been sitting on my roof, upsetting the neighbours. I still
have some tweaking to do to get reliable images, but all in all it seems
to work rather well for $76.

Regards,


David Perry