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Old January 14th 07, 04:58 AM posted to rec.radio.amateur.policy
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First recorded activity by RadioBanter: Jul 2006
Posts: 199
Default One way to promote learning of code ...

Jim wrote:
Stefan Wolfe wrote:
My reading would be, computer "CW" (with sound card output electrically
coupled to mike input and does not operate true A1A), is still legal in

the
CW sub-bands provided the data coupling from computer to radio is

electrical
and not acoustic.


Doesn't matter.

This would imply, of course, that computer programs for CW are not
acceptable (even if legal) across the entire CW allocation unless the

output
actually "keys" the CW carrier. They are NOT equivalent to CW.


Yes, they are. Or rather, they can be.

If you have an ideal SSB transmitter, and you feed an ideal sine-wave
audio tone into it, you get a pure carrier output. Key the ideal
sine-wave audio tone, and you have a keyed carrier.


....offset from the (nulled) carrier frequency, by the pitch of the audio
tone.
LSB: 7.025 MHz - 440 Hz = 7.02456 MHz.
USB: 7.025 MHz + 440 Hz = 7.02544 MHz.

Now of course if the SSB transmitter or the sine-wave isn't ideal, you
wind up with unwanted outputs, such as the suppressed carrier or the
unwanted sideband. How much suppression is needed is another matter,
but I suspect that with modern methods the unwanted products could be
kept low enough not to make any difference.

The big question is whether the signals (keyed carrier vs. keyed audio
tone) look different on a spectrum analyzer. If they don't, why should
FCC care?


And, for decades, it's been exceedingly simple to create a very low
distortion sinewave at audio frequencies. Prior to digitally synthesized
oscillators, the best known was (is?) a Wien Bridge oscillator:
http://en.wikipedia.org/wiki/Wien_bridge_oscillator.


73 es KC de Jim, N2EY


73, Bryan WA7PRC


 
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