As you know, Continuous Waves have no Amplitude Modulation so they can't be detected by a simple diode. You would only hear a click as the signal began and ended.

Because of this, various methods were used in the receiver to impart some artificial amplitude modulation. Besides the mechanical interrupters you have described, there was the "Ticker" and various other tone wheels, as well as a motor-driven variable capacitor which rapidly brought the tuned circuit in and out of resonance.

After the Hetrodyne detector was invented these mechanical CW detectors rapidly went out of use.

Decoding a SSB signal is exactly as you describe. The signal is mixed with a "period correct" local oscillator (eg BFO) so as to generate mixing products in the audio range. Simply placing a transistor radio near your Xtal set will do the job if its Local Oscillator (or a harmonic) will tune across the required frequency.

Interesting stuff indeed.

............. Zim

Certainly if you Amplitude Modulate the incoming signal (via a spinning capacitor, etc), you could then use a diode to detect the resultant AM signal.

But most Ticker circuits I have seen don't use a diode: The ticker somehow manages to directly detect the incoming RF.

I am guessing that by randomly chopping the RF (abrupt on/off), the Ticker is creating wide-band modulation products (sidebands), some of which extend down into the audio range, and it is these products which can be heard in the headphones.

............. Zim

a google search on "Poulsen Tikker" or "Poulsen Ticker" turns up many other references, but I haven't yet seen a good explanation of how they actually work.

................ Zim