Re: [Discuss-gnuradio] WBFM modulation. Bad sound and aUaU

[Marcus D. Leech]

On 03/04/2017 06:58 PM, Fernando wrote:
> Hi!
>
> I'm tryng modulation/demodulation in WFBF (I've tried too NBFM with same
> result)
>
> I'm using a HackRF one to transmit and a NI-USRP2920 to receive.
>
> I am using the attached block diagram
>
> If I bypass both osmocom, connexting TX signal to RX, the system works
> fine, but when I do TX and RX through both  osmocom it sunds very badly
> and I get the followind log:
>
>
> linux; GNU C++ version 5.3.1 20151219; Boost_105800;
> UHD_003.009.002-0-unknown
>
> Using Volk machine: sse4_a_64_orc
> gr-osmosdr 0.1.4 (0.1.4) gnuradio 3.7.9
> built-in source types: file osmosdr fcd rtl rtl_tcp uhd miri hackrf
> bladerf rfspace airspy redpitaya
> -- Opening a USRP2/N-Series device...
> -- Current recv frame size: 1472 bytes
> -- Current send frame size: 1472 bytes
> -- Using subdev spec 'A:0'.
>
> UHD Warning:
>      The hardware does not support the requested RX sample rate:
>      Target sample rate: 2.640000 MSps
>      Actual sample rate: 2.631579 MSps
> gr-osmosdr 0.1.4 (0.1.4) gnuradio 3.7.9
> built-in sink types: uhd hackrf bladerf redpitaya file
> Number of USB devices: 19
> USB device 1d50:6089: 000000000000000071c469c82d291f43 match
> Using HackRF One with firmware 2017.02.1
> gr::log :INFO: audio source - Audio sink arch: alsa
> Ulen(interp_taps) = 350
> aUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaUaU
> > > > Done
>
> It is that it is too much for my system or it is that I am doing
> something wrong.
>
>
> regards
UHD is giving you a warning about an unsupported sample rate.  That 
likely will cause things to be awful.  Where did a sample-rate of
  2.64Msps come from?    Gnu Radio doesn't automatically "match" 
mis-matched sample rates between a source and a sink--your flow
  graph has to do that--just as a compiler for ordinary programming 
languages cannot "do what I meant to do, not what I typed", neither
  can Gnu Radio "intuit" what your intention was.