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Old January 14th 07, 10:37 PM posted to rec.radio.amateur.policy
Michael Black Michael Black is offline
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First recorded activity by RadioBanter: Jul 2006
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Default One way to promote learning of code ...

"Stefan Wolfe" ) writes:
"Michael Black" wrote in message
...

If it looks and sounds like CW, then it is CW.


If the carrier of a double sideband AM signal is not keyed on and off, it is
not true CW, no matter how it sounds.

I think the problem is that you are incorrectly equating A1 "CW" to A2 "MCW"
(tone modulated continuous wave).

NO, I'm talking about resutls.

We weren't talking about double sideband, presumably with a carrier.
We were talking about an SSB transmitter.

You can't get a signal that "looks and sounds like CW" if you feed
an audio tone into a transmitter that has a carrier, and/or has two
sidebands. There will at the very least be the carrier and a signal
offset from that carrier by the frequency of the audio tone. If there
are two sidebands, there will be the carrier and then two signals (both
offset from the carrier by the frequency of the audio tone). In neither
of these cases will there be a CW signal.

But feed a pure enough sinewave into an SSB transmitter that has good
carrier balance and good unwanted sideband supression, and you have
a CW signal. It doesn't matter how it's generated, it matters whether
it "looks and sounds like CW".

If you were talking about whistling into an AM (ie dsb with carrier)
transmitter) then all you can ever get is "MCW", aka Modulated CW.

If I misread what kind of transmitter you were talking about, it was precisly
because there is absolutely no way you can get a CW signal by whistling
into an AM (DSB with carrier) transmitter. YOu were the one who said you
were a good whistler.

No, I went back and you were talking about a sideband transmitter.

The results are the results. YOu can't get a CW signal out of an AM
transmitter by injecting an audio tone into it. The output signal
will be the giveaway, and it doesn't matter what method you use.

But if you inject an tone into an SSB transmitter, the results will
be exactly the same as a CW signal, so long as the sinewave is pure
and that ssb transmitter is in good shape.

It's no longer "tone modulated" because you are only issuing a single
frequency.

An AM transmitter does not transmit a signal where the carrier goes
up and down in amplitude. It is a composite signal of three signals.
The carrier, which in effect gets to the antenna because of feedthrough.
Then the two sidebands. Feed a fixed audio tone (say 1KHz) into that
transmitter and you get three signals in the output of that transmitter, the
carrier, and the two sidebands at 1KHz above and below that carrier.
Obviously that can never be a CW signal. But it does show that the
modulating tone is translated to radio frequency. Suppress the carrier,
and the carrier is gone from the output, with the two sidebands still there,
which means two signals each offset from the frequency of the missing
carrier. Suppress the unwanted sideband from that, and you get a single
frequency, which is no different from a carrier out of a CW transmitter.

When you whistle into an SSB transmitter, it can't be CW for the simple
reason that it won't be a pure tone, and the microphone will pick up
background noise, and you will no longer have a single frequency output from
the transmitter.

ONe of your previous posts was about your interpretation of what was wanted,
but it wasn't about understanding what was being sent. The FCC or any
regulatory body doesn't care whether you key an RF oscillator on and off
to generate CW, or if you inject a tone into an SSB transmitter. They
care about the results. Hence if the tone isn't pure, or the SSB
transmitter is not suppressing the carrier or unwanted sideband enough,
then you have an amplitude modulated signal of some sort, and of course
it isn't allowed in the CW sub-band. But neither can you run an AM
transmitter in the CW sub-bands and start modulating it with anything
into the microphone input.

"Acoustic coupling" has nothing to do with what type of signal is
being sent, except so far as it affects the purity of the output signal.

You are confusing Modulated CW with using a pure tone with a good SSB
transmitter. The former will always be an MCW signal, the latter will
be a CW signal so long as things are well adjusted and pure.

Michael VE2BVW