Re: [Discuss-gnuradio] Noise floor falls ~5dB when TX is started

[Ruben Undheim]

Hey, thanks

You are right. I'm using the WBX-board. I wrote it in the first post, but I understand that
you didn't see it because of the mess with my split-up posting.;)

Anyway, I am using a simple indoor antenna, and I get the same result with a 2m whip as


a log-periodic antenna (which btw. doesn't have a the correct bandwidth 400MHz+).

Would what you suppose be the case even when the usrp_tx part is only initialized and not used at
all? (like I do with the simple script) 

What is strange is that the noise remains low for as long as the USRP is running after
I've run a script with the usrp.sink_c() and the script has finished. I hope there will be
another way of getting rid of the noise inside the receiving script, so that I don't have to

add the usrp.sink_c() in all scripts where I'm not going to do any transmitting!

Ruben

2011/5/5 Marcus D. Leech <address@hidden>

> Sorry, it was accidentally posted before I was finished writing...
>
> ...To make sure that I receive well, I
> made myself a simple script like this:
> #!/usr/bin/
> from gnuradio import usrp
> u= usrp.sink_c()
>
> and run that after I've started the board.
>
> Does anyone have any suggestion for what might be the cause of this
> strange behavior?
> What happens when the usrp sink is initialized that would cause the
> receive noise floor to fall?
>
> Regards, Ruben

YOu haven't said which daughtercard you're using.

My *guess* is that you're using the WBX.  In which case, during TX, the
RX chain has one fewer layers
 of switch between the LNA and the antenna port (RX2), which will
improve the noise floor a bit.

What is your antenna configuration?


--
Principal Investigator
Shirleys Bay Radio Astronomy Consortium
http://www.sbrac.org



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