Re: [Discuss-gnuradio] --width-8 in usrp_fft.py causes spectral artifact when using --waterfall

[Marcus Leech]

Eric Blossom wrote:

> Not sure abou the waterfall code.  OTOH, the reason we haven't been
> promoting this mode is that it does not currently perform proper
> rounding.  Thus the strong DC artifact.
>  
Yup, further investigation of width-8 reveals that it is currently too
 "artifacty" for actual use.  Having 8-bit samples working
 properly will be nice for radio astronomy at some point,
 but for now, 16-bit samples are working well for testing.

> Still there. It's called avg_alpha:
>
>
> class fft_sink_base(object):
>    def __init__(self, input_is_real=False, baseband_freq=0, y_per_div=10, 
> ref_level=50,
>                 sample_rate=1, fft_size=512, fft_rate=15,
>                 average=False, avg_alpha=None, title='', peak_hold=False):
>
>
>
>  
Thanks, Eric.  I did actually find it again shortly after posting my 
message, but forgot to
 send a "never mind".

I added a --avg option to usrp_fft.py to turn on averaging.  The next 
step would be to
 add a GUI control to control the averaging period--does the 
fft_sink_base code handle
 changing the avg_alpha in the middle?