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

From: Marcus Leech
Subject: Re: [Discuss-gnuradio] --width-8 in usrp_fft.py causes spectral artifact when using --waterfall
Date: Sun, 01 Jan 2006 11:47:52 -0500
User-agent: Mozilla Thunderbird 1.0 (X11/20041206)

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, 
                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?

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