For a CW signal, the nonlinearity of a typical power amplifier should
have the effect of shortening the rise and fall times. That does indeed
widen the transmitted bandwidth. But intuitively, it seems like the
distortion would have to be really bad to shorten the rise/fall times by
much. You could always compensate for it by adjusting the K3 for softer
key shaping.
Alan N1AL
On 12/22/2016 10:22 PM, Vic Rosenthal wrote:
I didn't exactly do this, but I did investigate the effects of distortion on CW
signals. I disconnected my P3 from the K3 and set the IF to 7 MHz. so it would
act like a standalone spectrum analyzer.
I was interested in whether a class-C amplifier I had built would sharpen the
keying enough to create noticeable clicks. The amplifier used minimal fixed
bias to allow a small amount of resting plate current in transmit mode, with
full class-C operating bias provided by a grid resistor.
I noted a broadening of the base of the signal on the P3, indicating that the
signal was not as clean as the K3 alone. But listening with another receiver
on either side of the S9+30 dB signal didn't reveal audible clicks. I also
asked other operators to listen and there were no reports of clicks.
I am sure that attempting to use that amplifier (a pair of 813s) on SSB would
have gotten me ridden out of town on a rail!
Vic 4X6GP
On 22 Dec 2016, at 23:10, K9MA <[email protected]> wrote:
On 12/22/2016 11:40, Jim Brown wrote:
IMD also affects CW. What we call CW is not "continuous wave," it is a
continuous wave that is 100% modulated by a rectangular wave. That rectangular wave is
rich in harmonics, and excites IMD. We hear it as clicks.
It would be interesting to see how much IMD it takes to significantly increase key clicks
of a "clean" keyed CW signal, like that of the K3. I'd expect the effect to be
small, compared to that on an SSB signal for the same level of IMD, but I could be wrong.
I suppose a simple test would be to have a local friend with a P3 watch the signal as I
turned down the supply voltage on my K3. Has anyone tried anything like that?
73,
Scott K9MA
--
Scott K9MA
[email protected]
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