[amsat-bb] Re: DSP Speaker

Tony Langdon vk3jed at gmail.com
Thu Apr 12 15:04:07 PDT 2007

At 02:04 AM 4/13/2007, Bob McGwier wrote:

>In the DttSP software, the sdr core for PowerSDR (Flex Radio) and 
>others,  we have a block LMS approach to automatic noise 
>reduction.  It does a really good job of doing noise reduction and 
>automatic notch (your choice) and it definitely does not introduce 
>nasty sounding distortion.  It is much more stable than standard LMS 
>based automatic notch filtering.    When I developed the 
>algorithm,  I was surprised that others had not done it.  I then 
>learned of some subtleties which do need mitigation but were pretty 
>straightforward.  You adjust the filter once per block rather than 
>once per sample, so you must be careful not to introduce 
>discontinues (distortion) at the block boundaries.  Once 
>handled,  this is the only way this should be done.
>That code is available for svn download (visit the Flex Radio web 
>site or the dttsp-linux yahoo group).

Hmm, interesting.  Need the radio to run this on though, to evaluate 
how well it performs. :)

73 de VK3JED

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