Re: how to stop the top_block and restart signal transmission

Hi Jason,

I really appreciate your help about the problem that I got. The info
related to the GNURadio and the USRP that I’m using is listed in the

Please confirm that you just see the carrier, not your modulated
signal when using the lock()/unlock()

I checked the result of using lock()/unlock() by correlating the down
converted signal with the Barker code, at the transmission pause
interval, there is no correlation peak. Therefore, it turned out there
is no code transmitted during the transmission pause interval. Is it a
right way to test if there is Barker code transmitted during the
transmission pause interval? Is lock/unlock working for completely
turning off the signal transmission for 5ms? However, I’m sure when
using lock/unlock method still gives at least carrier signal in the
pausing interval, which is observed on the oscilloscope.

Also, please tell us:

What version of GNUradio are you using?

The version of GNUradio that I’m using is GNURadio 3.2svn

What hardware are you using? USRP? which daughterboard?

I’m using USRP1 with LFTX daughterboard plug-in. (similarly, at the
receiver side,USRP1 with LFRX plug-in is utilized. )

Are you using UHD?

I’m not using UHD.

Thank you so much for all of your help!


Hi, Yan

I tried the similar python code as yours, as follows:

send_pkt(“payload”, eof=False)
print “before lock()”
print “after lock()”
print “before unlock()”
print “after unlock()”

I found out that, the last print is not showing up.

Do you have idea regarding to this issue?

Yan N. wrote:

receiver side,USRP1 with LFRX plug-in is utilized. )

View this message in context:
Sent from the GnuRadio mailing list archive at

The version of GNUradio that I’m using is GNURadio 3.2svn

I think there was some work in 3.3 for this sort of issue, but thats
just from memory, as I mostly use UHD these days.

Things you might look for:
python -c “from grc_gnuradio import usrp as grc_usrp;

there should be a set_enable() function on simple_sink_c which to the
best of my recollection would enable/disable the transmitter


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