I've noticed some possible confusion of the CW transmitter descriptions "Power Oscillator" and "MOPA".
I use these terms in this way:
"Power Oscillator" = one tube, one stage, oscillator feeds antenna directly. Can destroy FT-243 and later crystals, especially if optimized for maximum power output. Also can be challenging to get a good signal. Examples:
"MOPA" = two tubes, two stages, oscillator followed by an amplifier. Master Oscillator and a Power Amplifier. Easier to get a good signal Examples:
Examples of simple rigs with with three stages (addition of buffer/multiplier between oscillator and power amplifier):
Speaking very generally, I find the ease of achieving a good signal improves with more stages.
Steve WD8DAS
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