Posted by
P.B. Christensen on
Sep 19, 2009; 2:40am
URL: http://elecraft.85.s1.nabble.com/K3-Audio-Response-Version-3-33-Firmware-tp3673422.html
I have attached links to three .JPG images of the K3's audio response as
measured at
the headphone jack with SpectraPlus FFT software. Response passband was
normalized for both modes. SSB
is measured through the 6K filter, and CW through the 8-pole 2.8 kHz filter.
However, V3.33 SSB was taken with Fc = 1.35.
It would have made more sense to capture the responses such that three SSB
plots would overlay on one graph and three CW plots on a second, but that
took too much time in waiting for the firmware to load between plots.
Still, you can see radical differences between firmware versions in the
kinks below. Rx Band-1 EQ seems operational now too :-)).
http://216.229.20.37/images/K3-V325.jpghttp://216.229.20.37/images/K3-V330.jpghttp://216.229.20.37/images/K3-V333.jpgAs you can see, CW with V3.25 has the strongest low-end response relative to
1 kHz, but that can be compensated for with the first two EQ bands. Even as
it is, if you draw a horizontal line mid-way through the V3.33 plots, that
represents roughly +/- 2.5 dB from 20 Hz through 3.5 kHz. Not too shabby
for a
communications receiver.
As a further experiment, I just added 3 dB to Rx bands 1-3 and the response
is now essentially +/- 0dB between 20Hz and 3.5 kHz in SSB through the 6K
filter and Fc = 1.35. You can lay the ruler flat on the response.
http://216.229.20.37/images/K3-V333-EQ.jpgPaul, W9AC
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