[Skimmertalk] Skimmer Waterfall for CW
xdavid at cis-broadband.com
Sun Dec 20 23:01:29 PST 2009
I've lately wondered whether watching a waterfall display would be
useful for CW, particularly in a CW contest. As most contest rules
currently stand, the use of a waterfall is legal as long as it doesn't
actually decode anything. The operator is still required to know and
use CW ... it just happens to require a visual recognition and not an
aural one. I checked with CQWW and even a wide band waterfall like CW
Skimmer is allowed in unassisted categories if it is used in "blind
mode" (i.e, callsign decoding turned off) since it is not really much
different than a spectrum display.
The thing that intrigued me, though, was the ability for a waterfall to
provide a running record of signals, which would allow a user to look
back at information he/she might have missed in real time.
I tried several PSK programs, as well as audio analysis programs like
Spectrogram, but none came even close to CW Skimmer's waterfall display
for resolution and speed. I've now used it in two CW contests (CQWW and
ARRL 10m) with just the narrow band audio (typically between 200 Hz and
400 Hz bandwidth) from my Elecraft K3 fed into my computer sound card.
These are my preliminary observations:
1. I didn't very often find it beneficial to use the waterfall to
separate closely spaced signals since overlapping traces are virtually
impossible to read ... at least not quickly. My ear seemed to do a much
2. The waterfall is somewhat marginal for trying to copy weak signals.
It helps a lot to play around with the CW Skimmer display settings to
get the best visual sensitivity, noise discrimination, and contrast, but
at the very low end your ear will be more reliable. I currently have
Brightness set at 35%, Contrast at 50%, and Gamma at 40%, although I
strongly suspect those would not be optimum for other rigs or other
sound cards. I found it best not to use "Colors" ... it tends to make
the dots and dashes mushy on the display.
3. Unless you happen to directly recognize CW visually, I don't advise
trying to use the waterfall to decode a string of characters. I have
to convert the dots and dashes to dits and dahs in my mind before I can
recognize anything, and that takes too much time at contest rates. It's
simply a "different language".
4. It is possible to use the waterfall to quickly grab a character you
missed when it was being sent. CW Skimmer gave me as much as 12 seconds
of scroll when I expanded the window to the width of my monitor, and
that was plenty to check the last callsign or report that had been
sent. Numbers particularly stand out on the display since they have
five elements, so it was usually pretty easy to glance up and spot a
number if I missed it . Any character with all dits or all dahs also
tended to stand out. Trying to pick out anything in general was NOT
easy, though ... you have to decode stuff you already know to find the
portion you missed and the display keeps scrolling unless you use stop
it (see more on that below).
5. Callsigns like S56SI sent at high speed can be hard to follow by
ear, but they show up fairly well on the waterfall.
6. Machine-sent CW with normal weighting reads well visually. Some
hand-sent CW and most badly-weighted machine-sent CW with really short
dits and element spacings gets blurred on the waterfall, but then again
those signals often aren't easy to copy by ear either. Why some people
do that in a contest is beyond me. Reasonable strength signals with
proper weighting were recognizable at speeds above 30 wpm.
7. Make sure you aren't overdriving the sound card ... it distorts the
elements on the display.
8. Chirps and bad key clicks stand out quite well. Grab a screen shot
and send it to the offender.
9. Using the waterfall may be more practical when doing S&P rather than
when running. Much of the time when running I found the waterfall to be
a distraction and I was better off paying attention to the audio.
Having to mentally convert the visual display to audio in my head was
like generating my own QRM.
10. Unexpectedly loud callers sometimes seem to override my brain and I
copy them poorly ... it's just a weakness of mine. The waterfall
doesn't care, though (unless the signal is so loud that it distorts
badly), so the callsign is there for me on the display if I react
quickly enough to use it.
11. So far it isn't "natural" for me to use the waterfall. Much of the
time I forget it is there even when I might have found it useful,
although I think that situation would improve with practice. It helped
me to locate the CW Skimmer window immediately above the N1MM main entry
windows (for VFO A and VFO B, in my case) on the monitor.
12. At first I couldn't find any way to pause the CW Skimmer waterfall
without using the mouse, which then also required me to use the mouse to
get back to the N1MM entry window. By sheer trial and error I
discovered that the F9 function key acts as a toggle to pause/restart
the Skimmer waterfall if it is the active window, but that still
required using the mouse to get back to N1MM. What I needed was a
re-mapped key on the keyboard that would run a macro to jump to the CW
Skimmer window, simulate an F9 keypress, then jump back to the N1MM
window. The free (and quite powerful) application AutoHotKey came to
the rescue and the following script seems to do the job nicely, using in
this case the Pause_Break key :
Pause:: ;Change this key identifier if you want to use a
WinActivate, CW Skimmer
Whichever window (N1MM or any other application) is currently active,
pressing the Pause_Break key will determine the unique identifier of the
current open window, save it, jump to the CW Skimmer window, pause the
waterfall, and then return to the previously active window. It's all
very quick, and pressing the Pause_Break key again will resume the
waterfall in the same manner. This allows everything to be done from
the keyboard, which I find very important in a contest.
Possibly someone else will find this information useful. In my case, I
think that the time-delay feature of the CW Skimmer waterfall could be a
useful enough tool during a contest that it might be worth the effort
for me to become more proficient with it.
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