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Electrodeum Pitch Antenna
βecker Electrode

1.12.20

 The linearity and rich sound of this project revolves around this electrode concept.

Pitch Field Linearity is having a response that matches a piano keyboard layout note for note.

When you have ideal Linearity, you set one octave width to match the size of your hand for aerial fingering and all the other octaves widths will also match right up next to the antenna! 

With the Electrodeum Pitch Antenna no inline series chokes are used, this design is parallel tuning which simplifies and improves the response. This Pitch Antenna tuning is much more forgiving.

A theremin MUST have a good earth ground, often achieved by using your main power amp that has a three prong power plug into the wall receptacle. Connecting yourself to a theremin may work with budget digital stuff but the analog voice develops from nature and so the theremin must breathe.

LTspice by dewster

Unconsciously drawn on 8.15.19, the birthday of Lev Sergeyevich Termen for the 2020 celebration.

The Electrodeum ~900 kHz tuning is a Goldilocks zone validated by dewster


 

My setup tunes to 900 kHz

 

Note: Use a 1/2" (13 mm) stretch on the spring to create a tuned coil antenna. The spring has an light insulating coating between turns. 

Century Extension Spring (substitute at your own risk)
C-253 9/16" x 16-1/2" x .054" (14.3 mm x 419.1 mm x 1.372 mm)
16 turns per inch (approx. 252 turns at a ½" I.D. diameter)

Purchase at Amazon

The un-stretched C-253 spring end coil end to end should be 15 5/8" or 15.625" or 39.7cm

I insert a 1/4" wood square stick cut to size 16 1/8" or 16.125" or 41cm long. The ends press against the inside of the double loop mounting rings.

After the stretch it should be just over 16.125" or 41cm edge to edge between the end loops.

The base of the antenna is attached to a high current 3.3mh High Q choke to earth ground.

There seems to be a 3/8" (10 mm) variation in spring lengths from different vendors, always use the C-253. Add the 1/2" or 13mm stretch and hope it works.

Link - Plastic 3/4" or 5/8" id 18" Sleeve to keep circulating air off the sensitive spring/coil pitch antenna.  Arrived in 4 day USPS

That dangling choke mounts on the PCB. You may want to use a 21" length acrylic tube, it looks the nicest.

PVC sprinkler pipe will also work but not as pretty as clear acrylic pipe.


 

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Maybe the miracle of the 100 year anniversary is that all theremin designs can now feel and play the same... much easier!  Then sound and technique will be the main Thereminist focus. The value of the E-pro will then depreciate.
(< This is a warning E-pro owners like you should have bought the FANG stocks 20 years ago.)


 

Actual PCB Silkscreen Pitch Oscillator Side

Some Pitch Electrodeum facts:

Without the L - 3.3 mh pitch spring antenna base choke, perfect linearity is still there but the variable oscillator must be tuned more precisely to the antenna resonant frequency of ~900 kHz.

Even without an earth ground linearity is there, the spring tuning seems to stand on its own which is a benefit, why it may work with all theremin designs.

The
13 mm stretch in the spring is critical and less stretch is better than more. Also this keeps the springs coils from shorting side by side.

Using the base L4- 3.3 mh high Q coil to ground (5 ohms) the variable oscillator tuning becomes very broad, 850 kHz to 950 kHz. The L3 3.3 mh coil use for the mixer/detector which is lower Q will not work or enhance the performance.

My "guess" and it is only a guess is you want to connect a 10 pf cap from the "top" of the spring to the bottom while experimenting. Try the bottom of the spring and then the bottom below L4 which is ground.

There are thermal drift advantages by connecting the signal wire about 1/4 the distance up the inside of the spring/coil. This needs more experimentation.



The left side red line 2" (50mm) from the spring coil is G7, normal field compression begins here, that is 7 playable octaves. 

Demonstration by Valery S of St Petersburg, Russia

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