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

[Cinaed Simson]

On 03/04/2017 03:58 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.

The only thing we know about your computer is that it's a  64 bit linux
system. So the answer is maybe.

The HackRF has a DC spike - see

    http://www.greatscottgadgets.com/sdr

for an example of WBFM receiver and how to avoid the DC spike.

You'll probably need a tuner for the UHD too - there maybe frequency
errors in both devices.

Try running the devices separated but at the same time - the HackRF at
433 MHz and the UHD tuned to a local WBFM station and see if you any
audio under flows.

The quadrature rate is a little high - try reducing it to 192 kHz.

Shutdown some of the Qt frequency sinks and see it helps.

But I would make a wild eye guess if you're having audio under flows
when running both devices your computer may be too slow.

> 
> 
> regards
> 
> 
> 
> 
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