[TenTec] CW Key Clicks and Filters

[Alderman, Chester]

Jim....

I am an avid contester and QRQ operator. I participate in just about every
CW contest that I can find time for. Along with several long time friends, I
run rag chews anywhere between 60wpm and 120 wpm. I use an Omni 6 and an
Icom IC-781 driving a Titan amplifier to max when doing contest.

I seriously doubt that there were very many contest stations generating key
clicks during the contest as most contesters are pretty knowledgeable
technically. When contest season approaches they go through great pains to
make sure their station is working properly. Besides that, they know they
will catch hell from other contesters if they are producing clicks.

If you hear one station, during a contest, producing key clicks then it's a
pretty good conclusion that station has problems. If you hear a lot of
contest stations producing key clicks, it's a pretty good conclusion that
you have your receiver incorrectly set up, i.e., noise blanker turned on,
AGC set incorrectly, etc.

When I run QRQ QSO's, my QRQ buddies and I always check each other for key
clicks.  Key clicks are caused, on the transmitter end, by the rise/fall
time of the keyed waveform, typically anything shorter than one to one and a
half milliseconds, will produce keyclicks. I also monitor, with on
oscilloscope, my RF output waveform and on my Omni 6 and on my IC-781, the
rise time of my characters do not change, no matter what speed I'm running.
It is possible for the risetime to change IF one has poor power supply
regulation. That is, when you start running higher speeds, say in excess of
60 wpm, your power supply may not be able to handle the higher duty cycle.
But that is very rare in today's rigs.

I recall sitting on 40m during a recent CQ WW DX contest, running DX
stations. I was copying VERY weak European signals for a long period of
time. It suddenly dawned on me that the frequency that I was on had become
very quiet, that is, lack of QRM. Being concerned that something had
degraded in my Omni 6 receiver, I opened my rx bandwidth from 500Hz to 1.8kc
and was shocked to hear a S9+40 station 500Hz above me. Tuning down the band
I was equally shocked to hear another S9+40 signal 500Hz below me....the
amazing thing was with the 500Hz filter, I didn't even know they had
bracketed me. That coincidentally, was the exact moment that I really fell
in love with my Omni 6 !!

The Omni 6 will not key at speeds over 70wpm, a Yaesu FT-1000MP I used to
own was pure junk when trying to key it over 60 wpm, the IC-781 (Corsair
II's also) just run flawless at speeds over 60wpm. The Orion is spec'ed to
run full QSK up to 60wpm, so I doubt it's going to be a QRQ rig either. No
radio will satisfy everyone's nit-picking (I am a nit-picker) requirements,
ever though in my opinion the IC-781 comes darned close. Even though my Omni
6 will not run QRQ, the great receiver it has is a very satisfactory
compromise, FOR ME! 

I have no intention here to 'flame' you, but as mentioned before, when you
hear a lot of signals producing key clicks, etc., in my opinion, it's time
to look at how you have your own radio adjusted.

73,

Tom/W4BQF


From: Jim Reid [mailto:jimr.reid@verizon.net] 

Subject: [TenTec] CW Key Clicks and Filters

Hi,

Spent a few hours during the CQ CW DX test.  I was
particularly interested in finding pairs of close signals: one
very strong, other quite weak.  Of course I found many such.

However,  many of the close in "weak" ones could not be
copied,  even cranking in much DSP filtering of  the RX-340.
Why?  Strong key clicks from the  "near by" strong signal.

About 70% of the S9 and stronger signals (none more that
15 dB over 9 as heard here in KH6 land) were generating
various "bandspreads" of clicks.  ALL of the strong signals
which were operating at 37 wpm or faster were generating
harmful clicks to nearby weak signals.  

One theory suggests that the wide click bandwidths (generated by
very steep rise time CW waveforms) were "generated" on-purpose.
That is, to clear spectrum space!  My theory is:  the operators were
unaware of what was going on.  

I wonder if ALL rigs "click" at higher character speed,  maybe
only do so when the CW character speed is pushed  high,  that
is well over 35wpm.  I found very few operators going much over
38 to 40 wpm on the weekend,  but there were a few,  and every
one "clicked" over several hundred Hz on each side of the carrier.

These clicks are essentially not noticed unless you are listening
with 500 Hz or narrower bandwidth;  and very easy to hear when
tuning slowly up or down the band with 300Hz or more narrow DSP
bandwidths.  That is the way to find the weak,  far away stations:
slow tuning,  maybe in only 10Hz steps and using 150 or so Hz
bandwidth.  But this technique really goes "to pot"  when a strong
click generator is near by!

I very much anticipate my coming Orion in which I can tailor
the CW waveform;  I will not use a steep rise or fall time!
The Orion,  with proper use,  will not be a generator of these
harmful clicks!

Just thoughts I have following the past weekend.

73,  Jim  KH7M


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