[TenTec] CW Key Clicks and Filters

[Steve Ellington]

I must agree with Tom. Those DSP-only reveivers tend to emphasize key clicks
for some reason. This has been mentioned in QST reviews of at least one
radio.

Steve Ellington N4LQ.
----- Original Message -----
From: "Alderman, Chester" <CAlderma@ora.fda.gov>
To: "'Jim Reid'" <jimr.reid@verizon.net>; <dx-list@yahoogroups.com>;
<tentec@contesting.com>
Sent: Tuesday, November 26, 2002 6:57 AM
Subject: RE: [TenTec] CW Key Clicks and Filters


>
>
>
> 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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