Quite right Vic. A.M. MCW was *required" for any emergency maritime communications. Up until well after WWII, some ships still had crystal detectors as the 'emergency' receiver should the main receiver fail. In any case, A.M. MCW received on a superhet produced a very distinctive sound that made it stand out from other traffic and was required or any shipboard CW transmitter.
Unfortunately many marine radio operators never turned the modulator on. One of the biggest jobs I had when preparing a ship's CW console for the annual FCC SOLAS inspection was to get the transmitter working in MCW mode. After a year of collecting dusty salty grime, it was not uncommon to fire up the modulator and have the final amp tank circuit insulators or the antenna switch erupt in flames due to the much higher peak RF voltages produced when the signal was modulated. Lots of scrubbing with rags and alcohol was then required to get the carbon and salt grime off of all the insulators, HI! Some of the early commercial (1960's) SSB rigs offered CW capability with a built-in audio oscillator that fed into the transmit audio. That is not MCW, but pseudo CW. It would be CW if the audio oscillator was a perfect sine wave and the carrier and opposite sideband suppression were perfect so that the only RF transmitted was the sideband produced by the audio oscillator. But, of course, it never is... 73 Ron AC7AC -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Vic, K2VCO Sent: Saturday, June 15, 2013 8:24 AM To: [email protected] Subject: Re: [Elecraft] Point me to the note for sending CW when in, SSB mode 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. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
