Re: [Discuss-gnuradio] USRP/TVRX setting for ATSC receiving

[Eric Blossom]

On Wed, Mar 29, 2006 at 02:12:13PM -0800, mao mao wrote:
> Hi,
> I just started playing with USRP+TVRX board to get the
> ATSC signal. I am a little bit confused about the
> setting in the gnuradio software:
> 
> I attached TVRX on RXB, so what parameters should I
> use?
> there are channels, muxs, formats.. I am totally
> confused.
> 
> I tried decim rate = 8, then channel = 1, then format
> = 0x300, then mux = 0x32103210.
> 
> But I can only download 16MB/s data, that's only half
> what I want from USRP. If I use channel =2, or
> decim=4, I was able to download 32MB/s data off USRP.
> But what is the correct parameters I should use?
> 
> I also tried to setup the TVRX board. In San Jose, the
> strongest DTV signal is from KICU DT @701MHz. So I
> used 701e6 in tvrx.set_freq() function. and I also
> used -43.75e6 in usrp.set_rx_freq(). Was I doing the
> right thing?
> 
> Thanks!
> Mao

The tvrx_tv.py code is out of date.

If you're trying to capture samples into a file, use usrp_rx_cfile.py:

  $ ./usrp_rx_cfile -R b -d 8 -f 701M -N 40M -g <gain> output.dat

The example above will collect 5 seconds of data into output.dat
You'll need to experiment with the gain setting.  Probably easiest to
sort that out using usrp_fft.py.

If you're getting overruns ("uO" to stderr), determine if it's your
disk or USB host controller by using /dev/null as the output file.  
If you're still getting overruns, you've probably got an EHCI host
controller that's not up to the job.

I also suggest using a fairly high gain antenna pointed directly at
the transmitter.  You want the fft output to be as flat as possible.
Makes life easier for the equalizer.

I used a $40 antenna from Radio shack:

    50" Boom Length, 18 Element Antenna
    Model: VU-75 XR  |  Catalog #: 15-2151


Eric