[Discuss-gnuradio] Lock-Up Time for 2PSK Demodulation

[Kevin McQuiggin]

Hi All:

I have a .grc 2PSK demodulator working for the RDS subcarriers on FM radio 
signals.  I note however that it takes a couple of minutes for the PSK demod 
hierarchical block to settle and give me consistent good data.

I tried fiddling with the three timing parameters in the block but lock-up time 
is only marginally affected.  All work fine at default 2*pi/100.0, just that 
stabilization takes about 2 minutes.

I also looked into the code for the hierarchical block as well as the generic 
mod demod, but I found no real insight there. Obviously my lack of theoretical 
foundation.

Perhaps this related to the low data rate of RDS, 1187.5 bps.  I have the PSK 
demod running at 2 sps, i.e. 2375 bps.  My original sample rate is about 600k.  
I decimate through the chain before the demod block.

gnuradio version 3.8.7.1 (from memory), Ubuntu 14.04, USRP B200, 16 GB ram, i5 
processor.  USB3 connection.

Any advice would be appreciated!

Kevin

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