John,
You will likely notice the opposite difference between LSB and USB on
bands lower than 21 MHz.
You may not have the SSB filters aligned correctly. It is almost
impossible to get the SSB filters aligned for best results using the "by
the numbers" method used in the manual (although those numbers will
produce workable filters. The crystal centers marked on the crystal
envelope for the K2 and KSB2 are marked to the nearest 100 Hz while the
crystals themselves are matched to the nearest 10 Hz to create a crystal
set. That means that the numbers in the manual may be off by as much as
90 Hz. Refining that would take too much detail in the manual and might
just confuse builders.
There is a solution beyond the manual --
To refine the filters Both SSB and CW as well as RTTY if you want to add
data modes), use a wideband noise generator (Elecraft N-Gen) and observe
the passband setting(s) with an audio spectrum analyzer such as
Spectrogram or Spectrum Lab.
Part 3 of the K2 Dial Calibration article on my website www.w3fpr.com
has information that may be helpful to you. If you need Spectrogram,
look for the links near the bottom of the home page.
My experience in repairing and aligning K2s is that most all K2s that
come onto my workbench need refinement in the filter settings. I have
had many unsolicited comments about the improvement in the SSB audio
Both for RX and TX) after I align those filters properly. Place the -3dB
point of the low frequency slope for the SSB filters at 300 Hz and they
will work great.
73,
Don W3FPR
On 7/24/2013 6:27 PM, John Oppenheimer wrote:
Hi Ray,
I believe that your observation is normal. I performed a fresh CAL FIL
alignment on the two SSB modes, and tried your test, I get similar results.
When on 21 MHz, USB has lower frequency noise, LSB has higher frequency
noise.
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