[Premium-Rx] Filter phase response

[John Reed]

----- Original Message -----
From: "Adam MacDonald" <calvinf15 at earthlink.net>
To: "'John Reed'" <jreed at alum.mit.edu>
Sent: Wednesday, October 08, 2003 2:02 AM
Subject: RE: [Premium-Rx] Filter phase response


> John
>
> Thanks for the pointer to the interesting URL.  I am experimenting with
> software radio and digital filter design.  "brickwall isn't
> everything"...  Gaussian filters might work well for your noise (despite
> the impulsive nature of that low band noise.  That Gauss guy, he was
> into everything...
>
> Adam, N1GX

I'm way ahead of you on that one.  I've done a lot of experimenting with
audio filters: DSP, analog active and passive LC.  The best I've found for
lowfer CW signals is a sixth order Gaussian passband shape passive LC filter
with 30 Hz bandwidth.  Forget about the DSP filters for this application.
They are third on the list, following active switched capacitor filters.  LC
passive filters are the best.  No added noise, smooth filtering and the
Gaussian shape gives minimum ringing.  If you need to get rid of strong
carriers close to the signal you're after then some other spectral shape
would probably be better.

John Reed