Re: [Discuss-gnuradio] strange receiver behaviour with UHD

[Nick Foster]

It's likely that initialization of the board gain and frequency settings
will take some finite but non-zero amount of time to settle. It's always
a good idea to toss the first few samples until things settle down. The
settling time will be different for each daughterboard and should be
experimentally determined in your application.

--n

On Tue, 2010-09-28 at 15:15 +0200, Patrik Eliardsson wrote:
> Dear List,
> 
> We have made a test program using a source and a file sink (see fg.jpg) where 
> we are receiving a fixed number of samples (with UHD and USRP2 and WBX-card) 
> from an AWGN-generator (constant power -19dB).  If we plot the abs value of 
> the received signal we always see a "spike" in the 10 first samples (see 
> fig1) before the abs value settles to a more expected value. Sometimes 
> (seldom) there is no "spike" but the result is still not as expected, the 
> received data starts at a higher level and slopes down during a quite long 
> time before settling to a stable level (see fig 2).
> 
> Have we missed something or why does this "spike" occur? Is there some 
> initialization time in the hardware that we need to take into consideration 
> before we start to receive samples (recv) after setting all parameters?
> 
> Br,
> Patrik 
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