Hello Ernest Fardin: As you thought, synchronization loops in the PSK/QAM demod blocks may wander off if you input noise into those blocks.
I asked a same question before, and the answer was not to feed in any data to the QAM demod block when you think the transmitter is not on. I did not try this, but maybe power squelch block can do the trick. (Or, alternatively, maybe you can implement your own synchronization blocks and use a demod block that does not do synchronizations. I believe that you can use a constellation receiver block to do this.) Regards, Kyeong Su Shin On Tue, Oct 17, 2017 at 10:46 PM, Ernest Fardin <efar...@ieee.org> wrote: > Hi, > > I have a simple QAM16 loopback (Gray code, diff encoding, 4 sps) working > as follows: > > QAM Mod ---> Throttle ---> QAM Demod > > This works fine if I have a constant signal level from the Tx. However, if > I add a variable gain between the Tx and Rx and drop the Tx level to zero, > then restore the Tx signal after a short time, the demod no longer works. > I'm guessing a control loop inside the demod has wandered off during the > interval with no signal. Is there any way to re-initialise the demod block > to help it find its way again? > > The objective is to simulate a 'bursty' link where the Tx is not > permanently keyed. > > Thanks in advance! > > Ernest > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio > >
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