Very well explained Deacon. I hope everyone will read this several times.
The topic of key clicks is just as simple and understandable as Deacon has
outlined in his post.
Tom/W4BQF
From: Dave Shrader [mailto:david.shrader@attbi.com]
Sent: Monday, November 25, 2002 9:17 PM
To: Jim Reid
Cc: tentec@contesting.com
Subject: [TenTec] Re: [dx-list] CW Key Clicks and Filters
40 wpm has a 3 dB bandwidth of somewhere between 200 and 300 Hz. So,
some 'key clicks' will be noted within a 500 Hz bandwidth due to filter
shape factors [bandwidth at -60 dB] in the receiving radio. Another
source of false 'key clicks' is the third order intercept in the
receiving radio. Strong nearby signals cause the receiver to desense
slightly. This modulates the AGC in the receiving radio. If the
offending signal causes key clicks at S9+15 but not at S7 then the key
clicks are being generated in the receiving radio. If the offending
signal has key clicks at S9+15 and also at S2 then the keyclicks are
from the transmitter.
True key clicks are caused by excessively fast rise and fall times of
the keyed signal. They are not caused by the power level of the radio or
the amplifier.
Without a scope and a spectrum analyzer it is virtually impossible to
truly say a signal has 'key clicks' even though you or I may hear key
clicks in our radio!!
Deacon Dave, W1MCE
Jim Reid wrote:
>
> Hi,
>
>
> 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. Some rigs just do this because
> of their design (FT-1000D and MP's are so reported, see for example:
> http://lists.contesting.com/_yaesu/1997-December/001420.html ;
> or even linear amp problems at high speed, see for other info:
> http://www.amrad.org/pipermail/lf/2000q2/000433.html ;
> unfortunately the site by W8JI is still down, as it has
> much info about eliminating key clicks).
>
>
> 73, Jim KH7M
>
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