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Re: [Discuss-gnuradio] Questions about WBX daugtherboard

From: Jason Abele
Subject: Re: [Discuss-gnuradio] Questions about WBX daugtherboard
Date: Thu, 18 Mar 2010 09:48:44 -0700
User-agent: Mutt/1.5.20 (2009-06-14)

On Wed, Mar 17, 2010 at 04:09:09PM -0700, Damien Serant wrote:
> Hi everybody,
> I received few days ago my new URSP2 with the WBX daugtherboard and i have
> some questions. 
> First there is two input: one labeled Tx/Rx and the other Rx2. Why is there
> two Rx input and which one i have to use for reception ?

TX/RX is used for half duplex operation and can be either TX or RX, RX2
is used for RX-only or full duplex operation.  

The input can be selected with the -A switch to usrp_fft.py, which
appears not to have been added to usrp2_ffy.py yet.  Thus, the default
on usrp2_fft.py will be to use the TX/RX port.

> Second, for my first test i plotted the spectrum of received signal (without
> any antenna) by using the usrp2_ftt.py example script. Looking at the
> spectrum shape it appears there is a passband filter of about 8MHz bandwidth
> somewhere in the reception chain.  I believed, according to datasheet, that
> the bandwidth was 30 MHz. An explanation ?

The bandwidth is roughly 30MHz, perhaps you have your decimation rate
set to 100M/8M = 12.5 .... so maybe 8 or 16?

> Third, the same spectrum shows lot of spurious harmonics relatively powerful
> (compared to the noise floor). Is it normal ?

There are clock multiples that show up, what sort of spurs are you

> Thanks in advance for your answers.
> Damien 
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