[Elecraft] K3 APF

[Joe Subich, W4TV]

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
>
>