http://elecraft.85.s1.nabble.com/8-pole-vs-5-pole-I-knew-this-would-happen-tp446796p446815.html
an FM sized filter there.
FM and AM are 'features' also I guess...
FM, AM, SSB, and CW.
work well, and that is the main trick going on in the K3.
Then you get all those DSP extra goodies...
> -----Original Message-----
> From:
[hidden email]
> [mailto:
[hidden email]] On Behalf Of Larry Phipps
> Sent: Thursday, May 03, 2007 9:12 PM
> To: Jack Smith
> Cc: Elecraft Discussion List
> Subject: Re: [Elecraft] 8 pole vs 5 pole..I knew this would happen
>
> I think the term "roofing filter" is misleading. A narrow
> filter at the
> first IF protects a receiver even better than a "roofing filter", so
> there is nothing inherently distortion reducing in using a
> wider filter
> at the first IF and then a narrower one later. The ideal
> situation for
> IMD would be a pair of matched narrow filters at both IFs. The real
> reason for a "roofing filter" it seems to me, is to allow passband or
> slope tuning. This compromises IMD and AGC performance for
> the sake of a
> feature... which may or may not be valuable to the user.
>
> Therefore, the "roofing filter" should be termed the "passband tuning
> enabling filter", or "PBTE" filter ;-)
>
> Thankfully, I think Elecraft has done a brilliant job of
> giving us the
> options we want without compromises. By tying the DSP
> bandwidths and PBT
> functions to the "roofing filters", we have the ability to have the
> combination of 1st and 2nd IF BW we want,,, and with the variable
> "roofing filters", I think we will be able to almost set the relative
> BWs between the two... allowing a window for PBT or not as we choose.
> This is an exciting development, and will be copied by many companies
> over the next year. Kudos to the design team on this.
>
> 73,
> Larry N8LP
>
>
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