Our simple one transistor Michigan Mighty Mite creates a CW (Continuous Wave) signal simply by powering on and off the circuit. Involving less than a dozen components, this is truly a spare design. Without some attention to the keying (Keying Shaping) and the type of crystal being used or how it is tuned for maximum smoke (TFMS) it could and will sound like crap. Crap here does not mean Cool Radios And Projects!
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The letter "K" ( _._ ) might look like this sent in CW. But this is pretty idealized waveform and given the items mentioned earlier might not be so clean.
Given the long stretches at the Board and Care where I am just sitting there while the XYL naps, my mind wanders to thoughts of CW generation using other topologies.
Those with SDR radios who operate CW -- ever wonder how you generate CW using I/Q or DDC. Well, I am not totally sure how it is done but it certainly more than keying a single 2N2222A.
Most likely the CW generation in SDR involves a generated audio tone that with filtering appears like a brick wall square wave which is then translated in a mixing process to the operating frequency.
Then I thought about Modulated CW and in an attempt to be accurate looked up MCW. Here is what Wikipedia said.
Modulated continuous wave (MCW) is Morse code telegraphy transmitted using an audio tone to modulate a carrier wave.
Continuous wave (CW), by contrast, does not use a subcarrier, so there is no emission at all between Morse code symbols.
MCW can be generated by any AM or FM radio transmitter with audio input from an audio oscillator or equivalent audio source.[1][2] When an SSB transmitter is modulated by Morse code of only a single audio frequency, the resulting radio frequency emission is J2A or J2B and therefore is CW by definition, not MCW.[3]
Using a divining rod as a magic decoder ring, this I think is saying were you to modulate an AM signal with an audio tone, when no audio tone is present then you still have the carrier present. Whereas if you use SSB (no carrier) then on key up no carrier so true CW. I would think this might extend to a DSB transmitter that has no carrier. So, using DSB would not be MCW but CW.
When I built the MC1496 Direct Conversion Receiver using the Motorola (On-Semi) data sheet there was a schematic for a DSB Transmitter. I tried my hand at a DSB transmitter using the MC1496.
So, what if we built another MC1496 configured as a DSB transmitter and introduced an audio tone of around 600 Hz into the circuit and then we would have CW (by our Wikipedia definition). The Arduino Code for the DCR could be modified for the DSB transmitter with the necessary control circuits and generating an audio tone already exists.
This could be yet another way to do the CW transceiver. As of now this is just a brain message sent to me at 3AM this morning. It is not ready for prime time -- just yet.
More thought is needed on this approach but HAS a huge advantage if it can be pulled off. You would have both a CW and SSB (well DSB) transceiver with no Filter to be fiddled with using a questionable Nano VNA.
TYGNYBNT
73's
Pete N6QW