Posted by
KENT TRIMBLE on
Nov 13, 2010; 10:29pm
URL: http://elecraft.85.s1.nabble.com/K3-APF-tp5735159p5736365.html
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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