[Elecraft] K3 Filter Characterization using Spectrum lab

[Dave G4AON]

On my K3, the differences are negligible. I've checked with Spectrum Lab 
using 2.8 KHz, 6 KHz and 400 Hz filters (all 8 pole).

There is a slight roll off from around 500 Hz down to 100 Hz or so. This 
can be flattened by boosting the lower frequencies with the RX equaliser 
by about + 2dB. USB and LSB look the same and there is no significant 
difference when the bandwidth is increased beyond 2.8 KHz using the 6 
KHz filter. Audibly there is little difference between USB/LSB or CW/CW 
reverse.

73 Dave, G4AON
K3/100 #80 firmware 1.96/1.73
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I have noticed significant and unpleasant audio filter spectrum shape
differences by ear when I change filter bandwidths as well as change from
LSB to USB or CW to CW reverse.
This is not an issue at CW filter bandwidths but can be annoying at phone
bandwidths using the 6 KHz filter. When LSB is equalized for a flat pass
band (minor tweaks), USB audio is highly skewed at high frequencies. Level
at 2.7 KHz is 14dB above the level at 500 Hz in USB.

<SNIP>

Mike Scott - AE6WA