[Elecraft] K3 APF (alpha 4.21)

Sat Nov 13 17:42:13 EST 2010

I agree, I like the newer version as the ringing is much less now.
Jim K4JAF

----- Original Message ----- 
From: "K9ZTV" <k9ztv at socket.net>
Cc: <elecraft at mailman.qth.net>
Sent: Saturday, November 13, 2010 4:29 PM
Subject: Re: [Elecraft] K3 APF (alpha 4.21)

>I agree with Joe.
>
> My first impression was a "quieter" APF (if that's the right word).  The
> "peaking" is certainly there, and signals that are not copyable at 50
> cycles are definitely copyable with the new APF activated (provided
> there is a copyable signal at all).  But the peaked signal doesn't take
> your breath away like it did on the earlier version.  Frankly, I prefer
> this newer "tamed" (if you will) iteration.  It certainly has less
> ringing.  You can't have both "blasting" and "no ringing" at the same
> time.  There has to be a sweet spot and I believe version 4.21 nails it.
>
> I think there was some early confusion about what exactly is "frozen"
> when the APF is turned on.  It is the SHIFT that is locked, not the
> WIDTH.  The WIDTH control is still fully functional in APF mode with the
> bandwidth still being clearly indicated both numerically (0.05 and up)
> and by the normal width-varying graphic.  When the APF is turned on, the
> normal DUAL PB icon we have grown used to that incorporates
> upward-pointing winglets is still displayed, but in APF mode the
> winglets are positioned at the extreme ends of the line and are fixed.
> They do not change position when the WIDTH control is rotated (as they
> do when in normal DUAL PB mode).  The middle-bars between the winglets
> that show passband width DO change (as they always have) to visually
> indicate the change of bandwidth.  Fixing the winglets and locating them
> at the far ends of the graphic display is a great idea and gives further
> feedback that you are definitely in APF mode and not DUAL-PB mode.  I
> doubt anyone will confuse the two because (as in the earlier version)
> you have to enable the APF mode in menu item CONFIG: DUAL PB.
>
> The SSB problem in version 4.18 that required higher settings of CMP and
> ALC has been fixed.  My MH2 microphone delivers the recommended 5-7 bars
> of ALC and 2-3 bars of CMP at MIC=16 and CMP=13.  These are the nominal
> settings I have always run when circumstances force me to pull the mic
> out of the drawer.  For some reason the boys on the Missouri SSB Traffic
> Net get real agitated when I check-in using a paddle.
>
> Great job, Lyle, et al.
>
> 73,
>
> Kent Trimble, K9ZTV
> SN 21
>
>
>
>
>
>
>
> On 11/13/2010 2:35 PM, Joe Subich, W4TV wrote:
>> 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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