Posted by
Don Wilhelm-3 on
May 14, 2007; 6:53am
URL: http://elecraft.85.s1.nabble.com/K3-roofing-filter-group-delay-tp447425p447426.html
Brian and all,
The number of poles is not the primary deciding factor. It is the type
of filter (Cohn, Chebychev, Butterworth, Gaussian to 6 dB, Gaussian to
12 dB, etc.) that will influence the group delay. See the discussion on
filters in Experimental Methods for RF Design for further information.
In general, those filters with a 'rounded nose' will have the best group
delay characteristics - but that is only a generalization, the details
will tell "the rest of the story".
73,
Don W3FPR
Brian Lloyd wrote:
> A number of messages have gone back and forth here about roofing
> filters. We did mention group delay but I wonder if Elecraft can provide
> group delay characteristics for the various filters offered for the K3.
>
> Seems to me that, in general, fewer poles tend to provide better group
> delay in a filter at the expense of the skirts. OTOH, if the skirts in
> the roofing filter are sufficient to attenuate a strong, undesired
> signal so that it cannot cause desense, then it strikes me that the
> 5-pole filters might actually provide superior performance for digital
> communications.
>
> 73 de Brian, WB6RQN
> Brian Lloyd - brian HYPHEN wb6rqn AT lloyd DOT com
>
>
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