Spurious samples in data set?

GNU Radio
1

Hi

Attached is code i’ve used to write a signal to file and subsequently to
plot the samples.
additionally i’ve attached the plot.

Can anyone tell me what may be causing the huge spike at the beginning
of
the data set?

thanks,

Aadil

2

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Please don’t send attachments to the GNU radio mailing list.

It’s a known issue that the USRP sends some spurious large amplitude
samples right after it is enabled. You can safely ignore them.

  • -Dan

Aadil V. wrote:

[email protected]
Discuss-gnuradio Info Page

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3

On Tue, Nov 06, 2007 at 12:46:02PM +0200, Aadil V. wrote:

Aadil

Aadil,

There seem to be some issues with your acquisition code:

(1) you’re thowing away the the quadrature component of the complex
baseband signal from the USRP.

(2) you should be be using fg.start() / fg.wait(), not fg.stop().
It would be easier if you just used fg.run()

Eric

4

On Tue, Nov 06, 2007 at 11:45:59PM +0200, Aadil V. wrote:

Hi,

Thanks for taking the time to answer my questions.

I’d like to seek clarity on your first point, how am I losing the quadrature
component?

You’re using gr.complex_to_float, and then only using one of the two
output streams. You’re keeping the real stream and discarding the
imaginary stream.

I’m afraid i’m still working out exactly how some of these functions operate
and I may be missing something trivial.