Forum: GNU Radio usrp_source to file_sink ... what gets written when no transmission

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5b956b6b52e6bd83ad6da9815f4442a4?d=identicon&s=25 Mir Ali (Guest)
on 2009-05-20 10:53
(Received via mailing list)
Hi friends,

I have a usrp_source connected to a file_sink with Rx frequency 2.4GHz.
I
was experimenting with Tx and Rx using two different USRPs by
transmitting a
sine using sig_source block. I don't understand why is it that the
usrp_source writes some junk data to the file_sink even when I am not
transmitting from the other USRP. Is it possible that it might be
picking up
some stray signals at 2.4GHz?

Thanks,
Ali
A183460a6345f698900d4394de8212ce?d=identicon&s=25 Jason Uher (Guest)
on 2009-05-20 17:17
(Received via mailing list)
>  I don't understand why is it that the
> usrp_source writes some junk data to the file_sink even when I am not
> transmitting from the other USRP. Is it possible that it might be picking up
> some stray signals at 2.4GHz?

The USRP receiver has no idea when the transmitter is sending, all it
does it step down the signal and spread it out.  If there is nothing
there you will still get junk, especially if you are using some form
of agc which will make your amplitudes constant even if there is very
little power.

You can try to record only when the transmitter is on through
judicious use of gr.pwr_squelch_cc with the gating turned on.

Jason
5b956b6b52e6bd83ad6da9815f4442a4?d=identicon&s=25 Mir M. Ali (Guest)
on 2009-05-21 05:24
(Received via mailing list)
Thanks Jason.
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