I'll count this as another vote in favor of adding the Variable Q setting... At least a choice of 3 perhaps Wide, Med and Narrow. Even if one perceives the APF as "less ringy" and comments on it being a good thing, that means that they are happy to know that the Q got widened out a little, and things seem to sound "better".
> From:
[hidden email]
> To:
[hidden email];
[hidden email]
> Date: Sat, 13 Nov 2010 21:19:46 +0000
> Subject: Re: [Elecraft] K3 APF
>
> Joe wrote:
>
> > I did not make similar measurements with the original alpha
> > test version but this version seems subjectively less tight
> > than the original ... there is certainly less ringing with
> > this one but signals did not seem to "pop" like they did on
> > the earlier version when I tried it last night on 160/80/40.
>
> Joe, I agree with your subjective observation. No, the signals don't "pop"
> as much -- but there is less ringing. This is a trade-off, of course, and
> the precise balance of peak gain versus ringing is always going to be a
> matter of personal preference.
>
> I like this less-ringy version better, I think. Haven't had time to play
> with it a lot yet, but I will. I'm sure we will see many other opinions. So
> far, I think the current version is very smooth and adequately "peaky".
>
> (Opinion subject to revision upon more extensive usage.)
>
> Bill W5WVO
>
>
> -----Original Message-----
> From: Joe Subich, W4TV
> Sent: Saturday, November 13, 2010 20:35
> To:
[hidden email]
> Subject: Re: [Elecraft] K3 APF
>
>
> I made a similar set of measurements ... using the XG-2 and
> the AFV/dBV capability ...
>
> I measure the peak at 1 Hz wide (e.g. -.1dB +/- 1 Hz)
> the 1 dB points are 8 Hz wide
> the 6 dB points are 31 Hz wide
> the 20 dB points are 165 Hz wide
> the 30 dB points are 345 Hz wide
> gain is right at 9 dB.
>
> The measurements were made on 40 Meters with the XG-2 set to
> 1 uV and the K3 attenuator activated yielding a -108 dBm test
> signal.
>
> I did not make similar measurements with the original alpha
> test version but this version seems subjectively less tight
> than the original ... there is certainly less ringing with
> this one but signals did not seem to "pop" like they did on
> the earlier version when I tried it last night on 160/80/40.
>
> 73,
>
> ... Joe, W4TV
>
>
> On 11/13/2010 1:24 PM, Bill W4ZV wrote:
> >
> > For my own curiosity I did some measurements of the latest APF. They agree
> > with
> > measurements of the first release with the exception that the filter peak
> > is
> > now
> > zero beat instead of +10 Hz:
> >
> > Zero beat = 7040.021
> > Flat passband = 021-020 (both 0.0 to -0.1 dB)
> > -1 dB passband = 026-018 (-1.2 dB and -0.8 dB)
> > -6 dB passband = 037-009 (-5.8 and -6.0 dB)
> >
> > Flat = 2 Hz BW (at zero beat)
> > -1 dB = 8 Hz BW
> > -6 dB = 28 Hz BW
> >
> > I didn't measure the -6 dB BW carefully on the first pass since I was more
> > interested in the -1 dB BW, but this looks similar and agrees with Lyle's
> > 30
> > Hz
> > design goal. As mentioned previously, the -1 dB BW is important when
> > trying
> > to
> > detect signals below the noise floor since the human ear can detect this
> > difference in marginal conditions.
> >
> > I also checked the gain (APF vs not) which I didn't do before...+9.1 dB
> > which is
> > very close to Lyle's design goal of +9 dB.
> >
> > Nice job Elecraft!
> >
> > 73, Bill
> >
> >
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