FT990 keying -- how to cure choppy sounding CW (in all rigs)
Robert A. Wilson
Tue, 20 Aug 96 17:46:02 PDT
Ref: Note from N4LQ of Tue, 20 Aug 1996 16:01:35 -0400 (EDT)
Here are the rigs I know about that need a little help to prevent choppy
sounding CW when in QSK mode:
FT-990, FT-1000D, IC-761, IC-775DSP, TS-950SDX
Here are the rigs that do nearly perfect QSK right out of the box (at least
when the mechanical amp. relay is disabled):
FT-1000MP, TS-930, TS-940, TS-870, Omni VI
You can check this in any of the QST reviews that show a scope shot of the
CW waveform (though they don't always show it with the rig in QSK mode).
"Choppy" QSK rigs shorten all characters by a fixed amount, usually
between 3 and 12 ms (a dot at 40 WPM is exactly 30 ms long). Using heavier
keyer "weighting" can compensate for this, but only if you don't vary your
CW speed much. 60% weighting at 10 WPM adds a lot more milliseconds of key
down time than 60% weighting at 35 WPM.
The better solution is to use a keyer such as the Kansas City Keyer
(aka., Logitech K-1, CMOS Super Keyer II) that has a "K-factor"
setting. K-factor stands for "Keying Compensation Factor." If you
set it to 10 then every dot or dash is lengthened by 10 ms to
compensate for a rig that shortens every character by 10ms. The CW in
the sidetone monitor may sound perfect, but choppy on the air, so you
must use a separate receiver to listen to your transmitted signal when
you are setting the K-factor. Good CW ops can get pretty close by
ear, otherwise you'll need to use a calibrated scope.
Finally, some rigs only shorten the FIRST dot or dash, which indicates
a VOX timing problem or sticky relay. Using PTT instead of "VOX"
should cure it. Contest programs such as TRlog and NA provide a PTT
output to close the relay a few ms before the CW is sent. A
footswitch also works (if YOUR timing is good). :)