[Elecraft] K2 - LSB vs. USB

[Ron D' Eau Claire]

> Hello All:
> I have finally got all the filter setup correctly and have
> noticed one thing
> on SSB.  LSB sounds better in audio quality than USB no matter what I do
> with the BFO settings.  It just sounds clearer/cleaner on LSB. Yes I have
> installed the SSB filter mod.  Luckily on 18 Mhz and above the
> "better" SSB
> (USB in this case) is used.
> Any comments?

> Thanks,
> Sean - K3XT
> #2311

Sean, it sounds like you need the filter 'flattening' mod described on the
Elecraft web site? Go to "Builders Resources", "Mods" and click on "K2 2nd
Stage Xfil Mod, for 'Flatter' SSB Filter Response"

I notice it says "New" by it, but this issue of USB and LSB sounding
different was very hot topic when I built my K2 almost 2 years ago and that
was when I installed this mod in my rig.

It turns out that the "cleanup" filter at the output of the i-f strip has a
pronounced 'tilt' in its bandpass characteristic that makes SSB sound tinny
on one sideband and bassy or muddy on the other sideband. It is not a
problem on the narrower bandwidths used on CW, but is a real issue with SSB.

This mod does a very good job of eliminating it and providing a consistent
sound on either sideband. It only requires a few parts that you can probably
find in your junk box or, if necessary, pick up at Radio Shack. It does
require a 120 pf disc ceramic cap, which is not one of the 'standard values'
Radio Shack carries, but there is room to parallel up a couple of caps to
produce the correct value.

I strongly recommend this mod for ANYONE who contemplates SSB with their K2.
It made a very large improvement in the sound of the SSB to me. Indeed, back
in 2000 when I first saw the correspondence about it on the reflector here,
there was a comment from one of the Elecraft folks that it would be
incorporated in a future revision of the r-f board in the K2. Obviously,
that hasn't happened yet.

Ron AC7AC
K2 # 1289