[Skimmertalk] Skimmer Waterfall for CW

[David Gilbert]

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 
better job.

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 
different key
SetTitleMatchMode 2
WinGetActiveTitle,AB7E
WinActivate, CW Skimmer
Send {F9}
WinActivate, %AB7E%
Return

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.

73,
Dave   AB7E