Re: [Discuss-gnuradio] Questions about WBX daugtherboard

[Damien Serant]

Hi,
I forgot to thank you for your answers. So... thank you !
Concerning the spurs, they are peaks at precise frequencies. Their position
and their strength depends on the LO frequency  (I observe peaks around 698
MHz but not around 714 MHz as an example) but not on the decim rate. I
observed also an attenuation around the central frequency when I use LO freq
above 1 GHz. Note that the usrp2 is used without its top (i don't know if
this precision has any importance)
I'm not really clear and i can add prints screen if desired.

Thanks Again
Damien


Jason Abele wrote:
> 
> 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
> seeing?
> 
>> 
>> Thanks in advance for your answers.
>> 
>> Damien 
>> 
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>> 
>> 
>> 
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