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Re: [Discuss-gnuradio] USRP problems (interpolation, decimation, samplin
Re: [Discuss-gnuradio] USRP problems (interpolation, decimation, sampling rate, frequency)
Wed, 17 Nov 2010 09:04:47 -0500
On Wed, Nov 17, 2010 at 3:41 AM, Songsong Gee <address@hidden>
I use two USRPs. One sends a sinusoidal signal, and the other receives it.
A flow graph and a result are here
It seems fine, but notice that the receive signal goes 10 times faster than the original one. (see time-axes in both plots)
And lots of uO (usrp overrun). Don't think about uO because I run it on Virtual Machine, then what the hell is going on this flow graph?!
And I really wanto know the ratio of an interpolation and a decimation
I thought that interpolation:decimation = 2:1, because USRP sink processes 128Msamples/interpolation and USRP source processes 64Msamples/decimation
In order to match up both in same value, it has to be 2:1
In short, I want to know about 2 things.
1. RX goes 10 times faster than TX
2. ratio between interpolation and decimation
Your scope sinks aren't using the same sample rate. One is using 500, one is using 5k.
2:1 is correct for the ratio I believe.
Not sure what is causing your overruns.
Keep in mind that your true sample rate is being determined by your USRPs, not by your samp_rate variable.