[USRP-users] [Discuss-gnuradio] continous Tx voice transmission

franz kurniawan digitalturtle2010 at gmail.com
Wed Mar 6 04:47:58 EST 2019


Hi all,

i have struggling for couple of weeks in my AM transmitter project.
i use audio source (alsa) as input and USRP sink (B200mini) as output..
i know that this making a "2 clock problem" and it will create either
underflow "U" or building latency between microphone (audio source) and
resulted radio transmission after several hours of continuous running..
i have tried some solutions below but none is working well :

* set OK to Block to "No" in audio source to remove clock in audio source.
Previously i have modified the source of alsa_source.cc since in the OK to
block feature in alsa is ignored in current version of gnuradio.  But the
problem still persists

* using tagged stream to enable the burst mode of USRP. But also the
problem still persists

* manipulation of resampling rate with below formula:
interpolation : int(samp_rate * 1.000)
if i make the constant < 1.000 so that the consumer rate will be slightly
faster than producer rate, it will lead to repeating "U" , but there is no
latency.
else if the constant > 1.000 , there will be no "U" , but there will be
building latency..


So, is there any proper solution to this kind of problem?

Regards,
Franz
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