This may be a reasonable representation of the concept ?
http://www.ab4oj.com/icom/ic7600/apf.html
~Iain / N6ML
On Sun, Oct 24, 2010 at 4:55 PM, Ron D'Eau Claire <r...@cobi.biz> wrote:
> According to Icom (who has it on some of their rigs):
>
> "The APF changes the audio frequency response by
> boosting a particular frequency to enhance a desired
> CW signal... The peak frequency can be adjusted"
>
> So this is an adjustable frequency audio filter such as we've used for the
> past 3/4 century.
>
> As Doug, KR2Q, noted, the K3 is capable of a 50 Hz bandpass. That's about as
> narrow as a CW signal being keyed at 20 or 30 wpm can be fit into. Narrower
> will attenuate the CW sidebands so the dots and dashes start "slurring"
> together.
>
> I've used an audio filter many times and found them of very limited value to
> me if the receiver has a decent I.F. bandpass characteristic.
>
> That said, if it it's reasonable to implement, people want it, and it can be
> switched out, I'm all for it.
>
> Ron AC7AC
>
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