[Elecraft] APF vs 10 Hz DSP, why they don't sound the same

[Merv Schweigert]

Bill,  thanks a million,  I have difficulty explaining what is in the 
brain cells,
this helps a lot,  simple circuit,  and agree that running this through a
simulator would give the answers.  
I know some would not like the feature, but one does not have to use it.
Its the difference for me  of making the contact or not,  so a really 
big deal.
For causal operators they may never use it. 
73 Merv KH7C
>  > More generally, the APF proponents seem to have the problem that they
> treat it almost as magic.  If they could characterise what it does in
> terms of filtering, AF gain adjustment, distortion etc. it should be
> possible to simulate it in DSP, subject only to having enough processing
> power.  In particular, peaking just seems to me to mean turning up the
> AF gain in parallel with reducing the bandwidth. If that is all that it
> is doing, and if the K3 has soft AF gain controls, a plugin box could
> issue both commands in parallel.
>
>          The circuit in question is on page 54 of the FT1000 schematic below:
>
> <http://www.radioamateur.eu/schemi/FT1000_user.pdf>http://www.radioamateur.eu/schemi/FT1000_user.pdf
>
> The APF is around Q3016-2 (including Rs 3062, 3065, 3067 per the 
> "un-modification" sheet on N1EU's website below).  The circuit 
> schematic above has *not* been modified to the (incorrect) values 
> shown in the Yaesu service bulletin.
>
> http://n1eu.com/Mods/apf.pdf
>
> The FT-1000's APF is generally regarded by many as the best APF ever 
> done.  It should be possible to plug this into a circuit simulator 
> and generate a frequency response plot that Lyle can emulate in the 
> DSP.  I have a feeling that this is a very narrow and high-Q response 
> that is on the verge of ringing, but it should be possible to 
> duplicate the circuit in the DSP.
>
>                                          73,  Bill  W4ZV
>
>           
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>
>