I wish people would stop using the term 'MCW' for the method of
producing CW by feeding a (one hopes) clean audio tone to an SSB
transmitter. This is a way of generating CW -- which may or may not be
the best way -- but it is not MCW.
MCW as it has always been understood is a carrier modulated at an audio
frequency -- an AM signal. The signal is keyed on and off to transmit
Morse information, but it has two sidebands on either side of a carrier.
If the tone is, say, 600 Hz, then the signal will be at least 1200 kHz
wide. It is illegal in our HF CW bands.
MCW was used in past years for maritime communication because it can be
received by a receiver without a BFO and there is no 'zero beat'
phenomenon which could cause a listener to miss a signal.
On 6/15/13 3:40 AM, David Woolley (E.L) wrote:
Most modern commercial transceivers effectively generate CW as SSS
MCW. I think the K3 does it at about 15kHz or less, which is within
the audio range. I suppose the K3X could generate it directly, by
just keying the I signal to the modulator; however, that would mean
moving the VFO between transmit and receive, at the QSK rate. (Keying
I on the K3 would probably be a bad idea, as it would mean that any
transmit roofing filter would need to pass the first LO frequency and
therefore be subject to some carrier leak when key up, so I presume
that the CW is actually synthesized as fully fledged MCW. Even if it
keyed I, you could treat that as MCW with a side tone of 15kHz.)
Even the K2 architecture is effectively an MCW one, but in that case
the initial tone is in the MHz range.
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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