[Elecraft] K3 filter performance

[GW0ETF]

Hi,

No mention has been made in this thread about group delay and the dsp
filtering; my limited knowledge of dsp tells me that FIR filters are linear
phase so does that mean we should be using the (newly selectable) FIR
setting for data modes rather than the original IIR....?

73, 

Stewart Rolfe, GW0ETF (K3 145)


Don Wilhelm wrote:
> 
> Larry,
> 
> You are quite correct that all filters are not created equal.  For 
> digital modes, the group delay is just as important (if not more 
> important) than a flat passband and steep filter skirts.  In fact, those 
> filters with steep skirts often sacrifice group delay to achieve the 
> steep skirts - but I am generalizing here, and that may not be a 
> universal truth.
> 
> Unfortunately, group delay plots are not common for filters since steep 
> skirts seem to be the 'criteria of choice' for most amateurs.  A 
> Gaussian to 6 dB filter has a nice rounded nose and gentle skirts, but 
> has a great group delay characteristic, OTOH, Cohn filters usually have 
> great skirts and poor group delay in the passband.  Group delay will 
> make a difference in the ability to decode digital signals.
> 
> 73,
> Don W3FPR
> 
> 
> 
> 

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