15 Russian Theremin Schematics

To ILYA:

"All the coils are homemade. Advanced hobbyists were building the manual machine tools like that (the gear ratio is 20:21 to obtain сross-winding)":

I am not afraid of difficulties :))) Also, universal coil winder is beautiful device, BUT!!!... 

...Universal coil winder is unnecessary for  making Lev Korolyov theremins!!!

As Lev Korolyov wrote in Russian magazine "Schemotehnika" (2004, no1):

"The best way for making the windings  (...of the theremin coils - Alesandro) is to make winding by hands, using simple winding tool with 3:1 accelerating reduction gear and continuously swinging wire from one side of coil to another, imitating (sic! - Alesandro) universal winding".

"I have a simplest factory manufactured mechanism with the counter, like this"   ---Thumbs up!:

 "universal" coil = "honeycomb" coil.

16-th article:
S. Surov. “Tereminnote”, the microcontroller-based theremin.
“Radio” №12, 2013, p.21

Yet another toy theremin.

A discrete semitone pitch scale is used. The 100% intoned notes supposedly help the performer in accuracy.

Operation is based on variable pitch and volume resonance circuits which are stimulated by 20 MHz signal, generated by DD1 (ATmega88-20PU). This uC measures rectified voltages from resonance circuits and
synthesizes the audio, via the external DAC DA4 (KP752ПA1, the equivalent of AD7520).

Maximum (hand away) and minimum (hand near antenna) voltages correspond to “C3” (130.81 Hz) and “B6” 
(1975.5 Hz).

The power amplifier TDA2003 drives the 5W 4ohm speaker.

Coils have 8.5 turns each.

R1 is for pitch tuning, R17 is output volume control.
LEDs:
HL1 = “volume is maximum”
HL2 = “pitch is out of range (too low)”
HL3 = “sound is on”
HL4 = “pitch is too hight”
HL5 = “power on”

The sensitivity, pitch linearity and thermal stability are not specified.

FTP link to code is at the end of the article.