Re: [Discuss-gnuradio] GMSK receiver question, USRP tuning?

[Dan Halperin]

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The default decim in the C++ program (which, IIRC, is deprecated) is 8.
What decim (what bitrate?) are you using for GMSK?

- From the graphs, it looks like data from the C++ app is coming in about
4x too fast.

- -Dan

George Nychis wrote:
> Hi all,
> 
> I'm using benchmark_tx.py to transmit a GMSK sequence at 10MHz.  As some
> of you know, I'm trying to debug my own GMSK m-block receiver.
> 
> If I use test_usrp_standard_rx -F 10000000 (not the in-band receiver) to
> capture the incoming signal and plot it, I get the graph on the top, and
> if I dump the data coming out of the usrp1_source_c block when running
> benchmark_rx.py -f 10000000, i get the bottom graph:
> http://www.andrew.cmu.edu/user/gnychis/std_gmsk.png
> 
> I can successfully decode the transmission with my receiver using the
> data output from usrp1_source_c and benchmark_rx.py ... however I cannot
> decode it using the samples from test_usrp_standard_rx.
> 
> So I'm wondering, what is benchmark_rx.py tuning on the USRP differently
> than test_usrp_standard_rx?  Of course, my goal is to duplicate this
> action because my in-band code is also dumping data similar to the top
> graph.
> 
> Thanks!
> George
> 
> 
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