[Elecraft] What crystal filters for the K3 are linear phase delay (constant group delay) ?

[Larry Lopez]

Some of the wider filters in that paper are pretty good.
The narrowest filters are not so good.
The flat part of the passband has constant group delay.
The skirts are awful

For narrow filters it starts going weird.

Larry Lopez [via Elecraft] wrote:
> It turns out that the Elecraft 2.7 KHz 5 pole filter is the winner
> according to:
>
> http://www.qsl.net/gm3woj/k3filtertestssn2203.pdf
>
> which makes me want to make my own filter.
> Still, I'm going to keep the 400Hz 8 pole filter which
> is coming with my S/N 27xx Elecraft Radio !!!
>
>
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