Re: [Discuss-gnuradio] APT signals

[Berndt Josef Wulf]

G'day,

I managed to capture the spectrum emitted by NOAA-12 for its entire pass; not 
quite sure anymore which one it was. Using a Diamond D130 discone antenna and 
a low noise broadband power amplifier (10-2000MHz, g=20dB, nf=3.5, 
po=+20dbm!!!) the signal was recorded utilizing the usrp_rx_cfile.py python 
script, a  gain of 100, and decimation of 250 centered on 137.5MHz. It 
produced a very large file

-rw-r--r--  1 root  wheel  1117519872 Dec  9 20:01 noaa-12.dat

This a little more than 1GB!!!! and 419MB zipped. Do we have a place were it 
can be uploaded for other list members that are interested? My bandwidth 
isn't large enough to offer it to public from here.

I was surprised how loud the signal was, considering the equipment used here, 
and how well the TVRX card performed. Now I'm really looking forward to 
shooting the big birds  = geostationary satellites.

BTW: Do we have an AFC block to compensate for doublershift or is this 
something we still need to implement? I looked through the documentation but 
failed to find anything there.

cheerio Berndt

On Saturday 09 December 2006 16:52, Berndt Josef Wulf wrote:
> G'day,
>
> I'm looking for raw data. Don't you use the usrp_rx_cfile.py script to
>  capture frequency spectrum?
>
> e.g.: ./usrp_rx_cfile.py -d 32 -f 137.5M
>
> You may need to play with the options -R, -g, -N (subdev, gain and number
> of samples) depending on your setup where
>
> -R [A|B]                      site where the tvrx is plugged in
> -g <0..115>           gain (default is mid-point @ 58)
> -N <positive int>     number of samples (e.g samplerate * record time in sec)
>
> I usually have to specify the frequency and the decimation.
>
> I want to write my own decoder and an image sink to ultimately display the
> pictures received and hence audio files want do the trick.
>
> cheerio Berndt
>
> On Saturday 09 December 2006 14:29, Bill Tracey wrote:
> > Berndt,
> >
> > I can grab some APT audio with a USRP and Bob McGwier's rx apt code.   
> > Or are you looking for the raw data coming off the TVRF -- could probably
> > do that as well but will need some pointers as to how to grab the raw
> > sample off the TVRF card -- suppose one just takes the rxapt python code
> > and hacks it to dump to a file sink?
> >
> > I've also got a Hamtronics R139 I can grab audio from -- although it's
> > gotten a bit deaf  of late.  Pics from it can be seen @:
> > http://oddjob.yi.org:8888/wxpics/index.html
> >
> > Regards,
> >
> > Bill
> >
> > At 10:44 PM 12/8/2006, you wrote:
> > >G'day,
> > >
> > >Ok, let's try it this way:
> > >
> > >Is there someone with the equipment and time to record APT signals
> > >transmitted
> > >by NOAA satellites in the 137MHz band? Alternatively, geostationary
> > > weather satellites transmit WEFAX pictures at around 1691MHz (Hey, were
> > > are the guys that tuned into GPS spectrum which is right next door...
> > > :-)
> > >
> > >I want to demodulate the AM/FM 2400Hz sub-carrier signal and display the
> > >image. Currently I'm not in the position to capture the spectrum myself
> > > due to lack of equipment but this is about to change.
> > >
> > >I can provide info on satellite passes and frequencies for your
> > > location.
> > >
> > >cheerio Berndt
> > >
> > >On Wednesday 06 December 2006 14:20, Berndt Josef Wulf wrote:
> > > > G'day,
> > > >
> > > > Has anyone sampled NOAA or METEOR signals in the 137MHz spectrum
> > > > which they wouldn't mind sharing the spectrum data file(s)?
>
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