>If the CW mode sounds different than the FSK mode, there must be a
>difference in key shaping between the two modes.
There is, and this gets us right back to the Omni Six's CW transmit BFO
placement with respect to the 2.4 kHz I.F. filter: the two modes sound
different in CW because the FSK offset is well above the knee of this
filter's lower passband skirt, thereby producing waveform and note that is
subjectively more pleasing than in the CW mode. We've discussed the
work-around through the use of at least two different methods:
1) Tighten-up the filter's QC to allow the CW BFO frequency of 9,000.400 kHz
to pass well within the filter's linear range. The INRAD 2.8 kHz filter is
only one solution to this. With diligence, I'm sure Ten-Tec could produce a
much more accurate 2.4 kHz filter of their own and maintain the 2.4 kHz
bandwidth, provided that the they also improve BFO frequency temperature
stability.
2) In the CW mode only, bypass the 2.4 kHz filter with a small reed relay,
keeping lead length very short.
Technically, moving the CW BFO offset frequency upward will work, only
frequency display inaccuracy results as well an inaccuracy of "zero-beating"
with the sidetone pitch.
-Paul, W9AC
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