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Author Topic: CW waveform in QST product reviews?  (Read 453 times)
WB4PNE
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Posts: 17




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« on: February 12, 2006, 09:22:17 AM »


in their transceiver product reviews QST magazine publishes an oscilloscope tracing of the CW keying waveform.

can anyone comment on how to interpret this, e.g. what is a "good" waveform and what is a "bad" waveform?

how relevant is this information as far as evaluating the CW performance of a transceiver?

thanks!
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HA5RXZ
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Posts: 380




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« Reply #1 on: February 12, 2006, 12:04:53 PM »

A 'good' CW waveform will have a rise and fall time with a steady rf output in the middle. A 'bad' CW waveform will have straight sides with a near to zero rise time. The problem with a rapid rise and fall time is that it can generate key clicks.

Even worse is the problem of overshoot. On some rigs if you monitor the output waveform you may see a spike in the RF output at the beginning of a dot or dash. You're going to need a very good scope though to see this sort of problem.

HA5RXZ
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WB2WIK
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« Reply #2 on: February 12, 2006, 01:28:11 PM »

Straight, square edges are undesirable for sure, but not many rigs can produce those, especially at higher keying speeds.  Just as bad, to me, is mushy keying where the rise time is so long, you lose half the sent character and there's a big difference between the "key closer" waveform and the RF output envelope.  At slow speeds, probably doesn't matter; but at higher keying speeds, the long rampup cuts character elements and makes it hard to copy.

They usually comment on rigs that have really sloppy keying characteristics, otherwise they don't mention it.

WB2WIK/6
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WB4PNE
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« Reply #3 on: February 17, 2006, 11:59:49 AM »

thanks for the answers!  hopefully the product reviews will now make more sense to me.
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