Re: [Discuss-gnuradio] a report on dqpsk modulation in gnuradio

[Stefan Brüns]

Hi,

just a different suggestion - have you tried to determine if there is a 
frequency offset between the receiving and the sending USRP? I did some tests 
with the digital/benchmark_?x.py / qpsk code before the recent changes, but 
for me it worked quite well when I adjusted the center frequency of the 
transmitter or the receiver by their respective offset, eg:

./benchmark_tx -f 2.40001e9 ...
./benchmark_rx -f 2.4e9 ...

To measure the offset, I built simple flowgraph with a constant value as a 
signal source, which gives just a carrier, which should be (in an ideal 
world) at the selected center frequency, visible e.g. in usrp_fft.py

Hope this helps,

Stefan

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