Why the pitch antenna voltage is so important parameter? I has searching the forum and not found direct answer...
The pitch antenna voltage
Posted: 9/22/2015 5:04:41 PM
The antenna picks up environmental noise, so the theory goes that a larger antenna voltage swing will help swamp environmental noise and improve downstream SNR. Unfortunately there are currently no measurements to back this up, but it makes sense, no?
This is a fundamental aspect of Theremin operation that is crying out for a good nailing down. It's weird how little is known and published regarding Theremin design, someone should write a definitive text on the subject. I live in constant fear that I'm somehow barking up the wrong tree, wasting my time & disseminating disinformation.
To measure this one would need an LC oscillator with variable output voltage, where varying said voltage does not change other parameters in an overly complex manner. Interferers might have to be characterized as well. Not a trivial experiment IMO. The pragmatist would probably make the swing some tens of volts and just move on, figuring they did what they could. This is my current modus operandi (though I'm no pragmatist!).
Does anyone know the voltage swing on Theremin's designs? It's not too hard to measure via tiny series capacitance (1pF hanging off a scope probe).
Posted: 9/22/2015 9:49:25 PM
Wow! What keeps people from getting shocked when they touch the antenna? A natural damping of oscillation? Or are we into RF burn territory here? Not that I've ever heard of anyone getting shocked by a Theremin (more the other way around with ESD killing the Theremin).
Posted: 9/30/2015 10:28:36 AM
The linearization coils in series with the parallel antenna and hand capacitance form a voltage divider. While the antenna series resonant circuit is almost fully in tune with the VPO which gives a high resonance voltage at the antenna (up to 150V) when no additional hand capacitance is there, it gets more and more out of tune the more the hand approaches. When you touch the pitch antenna you have an overall capacitance of about 160pF instead the "free air" ~10pF, thus you are ways "out of tune" and there will be not longer that high voltage.
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