[Elecraft] [K3] Rx/Tx equalization band selection

[Don Wilhelm]

Mike,

All that effort may be an exercise in futility.
If I read your report correctly, you measured the roofing filter only. 
The full story is with both the roofing filter and the DSP filter 
engaged.  That will tell the story about what you hear, not just what 
the input to the DSP looks like.

73,
Don W3FPR

Mike Scott wrote:
> After plotting filter response on my 2.7 KHz filter
> I have been thinking about the Rx/Tx eq settings.
> 
> The current equalization scheme is 7 octave bands at: 50 Hz, 100 Hz, 200 Hz,
> 400 Hz, 800 Hz, 1600 Hz, and 3200 Hz plus an interloper non-octave band at
> 2400 Hz. I can guess why these bands, they match a popular external
> microphone equalizer product.
> 
> My filter is down 20 dB at approximately 100 Hz (from zero beat.) This
> number is from graphical construction where I only took data points every
> 100 Hz and plotted the results.
> 
> It would appear that the bottom equalizer band is beyond useful. Even with
> maximum equalization gain the 50 Hz spectrum is still way down. This tells
> me that we don't really have an 8-band equalizer as only 7 bands have
> utility. The 100 Hz band is questionable but barely within the zone.
> 
> Perhaps Wayne is going to open the lower end some more and then my issue
> could become moot and everybody would have to go buy a woofer. However
> whenever I try to equalize waterfall speckling I wish I had more granularity
> in the useful part of the audio spectrum.
> 
> If we wanted to start at 100 Hz and split the band between 100 Hz and 3200
> Hz into 7 equal fractional octave bands then sub octave processing would do
> that with band centers of 100, 178, 317, 566, 1008, 1796, 3200; then keeping
> with the theme, throw in an interloper band around 2400 or someplace useful
> to make an 8-band processor. The octave band centers above are 100 Hz
> multiples of the 6th root of 32 (3200/100.) The current scheme is 50 Hz
> multiples of the 6th root of (3200/50) which is the magical 2 factor.
> 
> Starting at 150 Hz instead of 100 (my favorite) may also make sense leading
> to band centers of: 150, 250, 416, 693, 1154, 1921 and 3200 with an extra
> one at 2500. Since these are broad anyway, why not call them 150, 250, 400,
> 700, 1200, 1900, 2500 and 3200 and give people the option of maintaining the
> current scheme or shifting to one of these? I kind of like having one of the
> filters centered on 700 Hz anyway. 
> 
> My 2 cents
> 
> 
> Mike Scott - AE6WA
> Tarzana, CA (DM04 / near LA)
> K3-100 #508/ KX1  #1311