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Re: [Discuss-gnuradio] New GR Tutorials Posted

From: Iain Young, G7III
Subject: Re: [Discuss-gnuradio] New GR Tutorials Posted
Date: Tue, 12 Aug 2014 22:30:45 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.0

On 12/08/14 12:41, jmfriedt wrote:

I am completing a summary of this summer's experiments including
* decoding weather satellite and the opportunity to introduce
channelized decoding (Frequency Xlating FIR Filter)

I guess you mean the NOAA POES Fleet, transmitting APT on around
137MHz ? Or are you up on 1691 MHz ?

I am also experimenting with decoding NOAA WX satellites at the moment.
Flowgraph (some of which borrowed from the afore-mentioned OZ9AEC) and
some raw and processed pictures are at http://hal.g7iii.net/POES/
Filenames have the format:

SC_RAW_DDMMHHmm.jpg  - Raw Files received off air. RF Front-end is
SC_MCIR_DDMMHHmm.jpg - MCIR Fake Colour Images
SC_NOIR_DDMMHHmm.jpg - Infrared Colour enhancement Images (Shows strong
rain storms rather well sometimes)

Where SC will be NOAA15, NOAA18, NOAA19 as appropriate, and DDMMHHmm
is the time/date of the pass, UTC.

I also have a modified flowgraph that resamples to 11025kHz, and sends
that to an alsa loopback device, to which wxtoimg is connected on the
other end.

That's actually how most of the pictures are created. While the output
from gnuradio is fine (although I have not done a back-to-back
comparison yet),

If you feed wxtoimg a raw image from Alex's/Mine flowgraph, it can't
tell when the pass was, or which spacecraft, so can't work out where to
draw the map. Most  annoying that it doesn't let you *tell* it where
the s/c was :)

Next pass I downlink, I'll remember to keep the poes.dat output file,
and run that back to back test...

Antenna system is a double turnstile at ~12 ft, no preamp, Funcube
Dongle Pro Plus, fed into Gnuradio. I must try the USRP and compare!

For those interested, some of the images are of the remnants of
Hurricane Bertha, after she had passed my location. Height of the
Antenna for those was only 7 ft, due to expected high winds (Antenna
is only mounted temporarily on a carbon fibre fishing pole!)


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