[USRP-users] FSK Radio 1 MHz tone spacing

Marcus D. Leech mleech at ripnet.com
Wed Oct 14 12:02:42 EDT 2015

On 09/24/2015 06:56 PM, Richard Bell via USRP-users wrote:
> Hello all,
> Ubuntu 14.04, GNU Radio 3.7.8, UHD 3.009
> I'm having issues with an FSK radio that works perfectly fine in 
> simulation with full synchronization and channel effects added (noise, 
> timing, frequency, gain attenuation). When I test it over the USRP 
> N210, I notice a frequency dependent gain that is applied to the tones 
> and what looks like instability in the frequency at each tone. The 
> output of the quad_demod block in gnuradio shows considerable 
> variability in what should be a single tone.
> So, I started to wonder if I'm pushing the N210 too hard here. My 
> tones are spaced 60 Khz apart and range from -450 kHz to +450 kHz for 
> a total of 16 possible tones. This amounts to what looks like a 
> frequency hopper, which is essentially what FSK is. Is that nearly 1 
> MHz wide frequency hopping band too much to expect? I'm running at 2 
> Msps.
> Thanks,
> Rich
I don't see any reason why this shouldn't work flawlessly.  This is no 
different than dozens of different OFDM applications that are used
  on a daily basis by USRP users.

I've taken the liberty of cross-posting to discuss-gnuradio, since some 
of this is likely Gnu Radio related, and not hardware related.

What gain settings are you using, and what daughtercard?

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