[Elecraft] APF measurements: FW 4.17 better results by 2 dB

[Arie Kleingeld PA3A]

Hello all,

Did some measurements on the different frimware versions. This time not 
a BW-plot but  I measured S+N/N ratio's.


I have no lab equipment but I have a K3 with dBV measurements, XG2 and 
the stepped attenuator from elecraft.
I measured the difference of the K3 dBV-reading in signal off (=N) and 
signal on (=S+N)
AGC off, mode CW, 400Hz BW and 400Hz Roofing.
RX gain of the K3 has been calibrated with XG2 and the K3 utility.


This is what I found.

_FW 4.25 and 4.21 (both give the same measurement values):_
At MDS level (stepped att on 20dB to reach this level)
normal 400 Hz BW: S+N/N  = 3dB  (as expected, hi)
400 Hz BW + dual PB: S+N/N = 10 dB

Now signal level 6dB under MDS (26dB att instead of 20dB):
normal 400 Hz BW: S+N/N  =   0.5 dB
400 Hz BW + dual PB: S+N/N = 4 dB


_FW 4.17_
At MDS level (stepped att on 20dB)
normal 400 Hz BW: S+N/N  = 3dB  (as expected)
400 Hz BW + dual PB: S+N/N = 12 dB (THIS is 2 dB BETTER)

Now signal level 6dB under MDS:
normal 400 Hz BW: S+N/N  =   0.5 dB
400 Hz BW + dual PB: S+N/N = 6 dB (THIS is 2dB BETTER)


There are probably people that can measure this far more better than I 
did with better equipment.
But this is what I can come up with here.

73,
Arie PA3A



Op 27-1-2011 0:52, Barry N1EU schreef:
> Forget it - full stop!
>
> I just ran a spectral analysis of the current firmware versus the very first
> APF implementation (mcu 4.17 dsp 2.65) from 11/3/10 AND THE PLOTS ARE
> ABSOLUTELY CONGRUOUS!  The APF implementation hasn't changed a bit (or a
> byte).
>
> Have a look:  http://n1eu.com/k3apf.gif
>
> magenta and green plots are taken with width = 200hz
> aqua and yellow plots are taken with width = 100hz
>
> Barry N1EU