Fw: Fw: [Discuss-gnuradio] AO-51 and GRC

[Patrik Tast]

Hi Alex,

I used method 3. Look at the spectrum and tune to the peak.

I didn't know about pyephem, must try it.

Thanks,
Patrik


> ----- Original Message ----- 
> From: "Alexandru Csete" <address@hidden>
> To: "Patrik Tast" <address@hidden>
> Cc: <address@hidden>
> Sent: Tuesday, December 08, 2009 22:33
> Subject: Re: Fw: [Discuss-gnuradio] AO-51 and GRC
>
>
> > Hi Patrik,
> >
> > Thanks again for the info. I like your home made yagi antenna for UHF.
> > I will try to build one in the holidays.
> >
> > Implementing Doppler correction in GNU Radio receiver can be
> > relatively easy. I can think of three ideas with increasing complexity
> > and performance:
> >
> > 1. Make the filter in front of the FM detector wide enough to cover
> > the satellite downlink +/- Doppler shift. I think for voice FM it will
> > be okay if you are a few kHz off as long as you get the whole signal
> > through the filter.
> > 2. Active Doppler correction using satellite tracking code. There is a
> > python library called pyephem that you can use to calculate satellite
> > position, range and range rate, hence Doppler shift:
> > http://rhodesmill.org/pyephem/
> > 3. Track the center frequency of the carrier using the FFT spectrum.
> > For voice FM this is easy because of constant amplitude. Even when the
> > signal is fading, the peak in the frequency domain will correspond to
> > the center frequency as long as you have decent SNR. You can try to
> > visualize it using a waterfall sink.
> >
> > Cheers
> > Alex
> >
> >
> > 2009/12/8 Patrik Tast <address@hidden>:
> > > Hi Alex,
> > >
> > > I used a 1.2 m long X-yagi and a cheap broadband TV pre-amp
> > > http://www.vekoy.com/product_info.php?cPath=85_402&products_id=12828
> > >
> > > EZNEC told me I should get ~14 dB Gain with this gadget, It sure works!
> > > The boom is a PVC pipe and elements are 3.2 mm Al/Ag TIG welding rods, < 
> > > $20
> > >
> > > An image of the antenna and txt how I made the X-Yagi is at
> > > http://www.poes-weather.com/~patrik/AO-51/
> > >
> > > It is tricky to follow the downlink frequency change due to doppler....
> > > Patrik
> > >
> > >
> > > ----- Original Message ----- From: "Alexandru Csete" 
> > > <address@hidden>
> > > To: <address@hidden>
> > > Sent: Tuesday, December 08, 2009 12:02
> > > Subject: Re: Fw: [Discuss-gnuradio] AO-51 and GRC
> > >
> > >
> > > > Hi Patrik,
> > > >
> > > > Thanks for the info. It's quite good reception you have with the TVRX.
> > > > Did you use any low noise amplifier in front of the TVRX?
> > > >
> > > > Cheers
> > > >
> > > > Alex
> > > >
> > > > 2009/12/8 Patrik Tast <address@hidden>:
> > > > > Hi Alex & All,
> > > > >
> > > > > I use the usrp_nbfm_rcv.py in examples to listen on OSCAR.
> > > > > Here is a sample audio recording I made a few week ago
> > > > > http://www.poes-weather.com/~patrik/AO-51/ 3.6 mb
> > > > >
> > > > > Patrik
> > > > >
> > > > > > ----- Original Message ----- From: "Alexandru Csete"
> > > > > > <address@hidden>
> > > > > > To: <address@hidden>
> > > > > > Cc: <address@hidden>
> > > > > > Sent: Tuesday, December 08, 2009 3:57
> > > > > > Subject: Re: [Discuss-gnuradio] AO-51 and GRC
> > > > > >
> > > > > >
> > > > > > 2009/12/8 Craig Kief <address@hidden>
> > > > > > > I need a little help. I want to do a project involving GRC. There is 
> > > > > > > a
> > > > > > > satellite called AO-51 (http://www.amsat.org/amsat-new/echo/). If 
> > > > > > > you
> > > > > > >
> > > > > > > watch some of the youtube videos you will see what most folks are 
> > > > > > > using
> > > > > > > this satellite for. It is great for using HAM licenses to do
> > > > > > >
> > > > > > > audio repeaters. I want to do this
> > > > > > > (http://www.youtube.com/watch?v=1HfvmU_utI8) with SDR. We have our
> > > > > > > ground
> > > > > > > station set up where we use nova software to drive our G5500
> > > > > > >
> > > > > > > rotators. We have a 144MHz antenna for TX and a 2.4GHz antenna for
> > > > > > > receive. We have a USRP-1 with a BasicTX and DBSRX for transmit and
> > > > > > > receive.
> > > > > > > We are using
> > > > > > >
> > > > > > > the GRC for our design work. What I want to do is be able to talk
> > > > > > > through
> > > > > > > a microphone and listen with a pc speaker on the
> > > > > > >
> > > > > > > rx side. My problem is that I am very new to GRC and am not positive
> > > > > > > about what blocks to use and what settings I should choose.
> > > > > > >
> > > > > > > Has anyone ever tried to do anything with AO-51 and GRC?
> > > > > > >
> > > > > > > Craig
> > > > > >
> > > > > > Hi Craig,
> > > > > >
> > > > > > I'm playing with GNU Radio and USRP for using it as ham radio
> > > > > > transceiver, though I'm still learning.
> > > > > >
> > > > > > Since AO-51 is an FM satellite it is relatively easy to have a quick
> > > > > > prototype up and running because there are already FM modulator and
> > > > > > demodulator blocks available in GNU Radio and GRC. There are even
> > > > > > examples for how to make FM transmitter and receiver in
> > > > > > /usr/share/gnuradio/examples/usrp/ or
> > > > > > /usr/share/gnuradio/examples/grc/usrp/ for GRC. For GRC I can only
> > > > > > find wide band FM receiver example, but you can simply replace the
> > > > > > wide band FM demodulator block with a narrow FM demodulator.
> > > > > >
> > > > > > I don't know how good DBSRX is above 2.4 GHz, I have only used it on
> > > > > > 2.2 GHz where it works very well. Otherwise there is the RFX2400 for
> > > > > > 2.3-2.9 GHz. Note the AO-51 is very often in V/U mode, i.e. uplink on
> > > > > > 145 MHz and downlink on 435 MHz and the DBSRX will not cover that.
> > > > > >
> > > > > > Cheers
> > > > > >
> > > > > > Alex
> > > > > >
> > > > > >
> > > > > > _______________________________________________
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> > > > >
> > > > >
> > > > >
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