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[Discuss-gnuradio] calcualted vs observed pulse length

From: seph 004
Subject: [Discuss-gnuradio] calcualted vs observed pulse length
Date: Tue, 29 May 2007 05:05:33 -0700 (PDT)

I've managed to store a sample set on the FPGA and transmit it periodically. The problem I'm experiencing is that the transmitted pulse is shorter than what I expected.

I worked out that by setting an interp value of 500 from python, that the FPGA interpolator would basically be set to 125 to go with the AD9860s x4. This would mean that to obtain a total rate of 32 Msamples/sec to the DAC, the data rate of the I and Q channels would have to be 16 Msamples/sec each, and thus 128 000 samples/sec each into the txchain modules. This should mean that if I provide a samples set of 128 I samples, and 128 Q samples, I should get 1 msec worth of complex output signal.

Is this correct? I'm not sure if I overlooked something. The result I get when monitoring  the output is about 750 microseconds  instead of
1 msec. Is there perhaps something I didn't take into account in the calculations? If anyone can assist it would be greatly appreciated.



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