Bill W4ZV wrote:
>
> The production start date for this mod could be in error on the webpage.
> I know this issue has been known about well before S/N 211. My S/N is
> early 100's and it definitely needed the mod.
>
I believe G4AON (K3 S/N 80) was the first to discover the CW rise time
issue. From his K3 review:
"There were no high power peaks when transmitting on low power and the
waveform of CW transmissions were smooth and clean when observed on an
oscilloscope. The rise and fall times were originally fixed and fairly soft
at approx 8 mS rise and 5 mS fall, not surprisingly there are no signs of
key clicks. A later change to the value of capacitor C222 (to 100 nF)
reduces the rise time to 5 mS. The time delay between the linear keying line
going low and RF appearing from the antenna socket is approximately 10 mS,
linears that are not able to switch in 10 mS would need to use the transmit
inhibit feature, QSK CW would be impossible with such a linear. A later
firmware upgrade is planned to offer variable time delays on the linear
keying line, for example the Kenwood TS-480 offers 10 mS or 25 mS depending
on QSK or semi-break in keying is used. The oscilloscope trace shown below
was triggered by the linear keying Voltage going low and shows a single
Morse "dit" at 20 words per minute, power output 10 Watts, this was taken
after changing C222 to 100 nF."
http://www.astromag.co.uk/k3/ (scroll down to CW waveform)
73, Bill
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