Lev's Antenna for the New Millennium

Theremin Linearity: With the year 2012 and the Awakening approaching so rapidly I should break my silence briefly about how perfect theremin linearity comes about.

The heterodyne theremin antenna is an electrode transforming current into radiated RF energy which is relentlessly looking for somewhere to go. Any conductive mass near the antenna will drain or absorb energy from the radiating pitch field.

Rather than a rod the Lev Antenna uses a spring coil which self resonates due to parasitic capacitance in series with a tuned LC inductor/capacitor. When your hand reaches into a linear tuned pitch field you will understand or feel what this tuning is doing. You will be able to align all your octaves with “perfect” linearity, from null point to the pitch spring antenna. The spread of notes can match a piano keyboard width, note for note, 5 octaves could be a 20" linear playing field. The number of available linear octaves is determined by the amount of RF energy a particular theremin design radiates into the pitch field. For the Theremax it will probably be just over three. The Lev Antenna is broad in tuning and very stable. Once set, it is not necessary to adjust again.

All my theremin experiments over the years used Hartley Oscillators operating between 800 kHz and 900 kHz. This higher frequency allows the design of the Lev Antenna to be more practical.

I found that using hand wound air coils in my theremin oscillators was a disadvantage and limited Perfect Linearity to just over three linear octaves. My RS Illusion theremin design revealed that using High Q ferrite coils would give more than five linear octaves. One secret of perfect linearity is revealed in the use of high Q oscillators and the high Q tuned antenna circuit.

This subject is covered in disorganized detail here: here (http://www.oldtemecula.com/theremin/ult_antenna/index.htm)

Any theremin design you are interested in, get sound bytes without the camouflage of excessive reverb. If no sound byte is available then be cautious of the designer’s experience at design.

Christopher
.

Dear RS Theremin, after having a look on your website, I got the impression that you have a more or less metaphysical approach to the antenna/capacitance/field model. You might be true, but there is no proof, as there doesn't seem to be one for the "capacitance only" model.

So I invite you to a kind of mathematical/physical competition:

You try to set up a physical model and the equations which prove that the "capacitance only" model is not sufficient to describe any theremins' behavior from a simple version with LC tank circuit only up to a version with a linearization with additional series coil, series coil plus series capacitor and finally series coil, capacitor and coil antenna.

I on my side will try to do the same, assuming that the capacitive effect between pitch rod and body/ground is sufficient to explain all phenomenons in all design variants mentioned above.

The deadline shall be June 14th, 2009, my 45th birthday.

Okay?

Hello Thierry,

[i]“I got the impression that you have a more or less metaphysical approach to the antenna/capacitance/field model.”[/i]

Thank you for the challenge which I consider very honorable, but I must confess something. I am not a musician, can’t even whistle. I am not an electronic engineer. Back in the 1950’s while most kids were playing football I was tearing apart many of those classic radios from the 30’s & 40’s. I was trying to figure out how something could work without moving parts.

Because of this it limits my posts to TW, unless a thread is actually one I might help to keep someone out of trouble.

In 2003 I was attempting to remake an AM radio transmitter using the single transistor circuit design I had used as a child in 1962. I had remembered the awe that inspired me of how an experience in simple physics could take on the appearance of witnessing magic. Theremin thinking at some point took over all my projects for a reason that today still has me scratching my head? I wish mathematics could explain it but neither can words.

My knowledge is from quiet observation and it will pass, this is why I webpage what I know. To just talk about theremins drains me and my hope is to inspire the thinking of today's youth that have so much . . . to remind them of the simple wonders and creativity us older folks once enjoyed.

Metaphysical . . . Interesting, I will have to look that word up! ‘-)

Christopher

Oh boy...

Don't let him fool you! Christopher has a lot more in depth knowledge than he lets on. He has certainly done lots of experimenting and cataloging results. That Lev antenna is intriguing. I hope Theirry can do the analysis. Personally Maxwell's equations do nothing but give me headaches! But I would love to see how they apply to describe the antenna circuit of a theremin with the Lev antenna in place.

Most discussions on antennas describe dipole and parabolic shapes. I haven't seen a writeup for a spiral antenna but maybe someone can find one somewhere.

Don

I have deep respect for practitioners and their empiric results. The latter are often better usable than lots of equations based on theoretical models which sometimes lack reference to reality.

I felt a bit needled by some statements without underlying reasoning on Christopher's website, not only concerning the Lev's antenna. If something works, I want to understand not only how but also why. With this I am in contradiction to the German proverb: [i]"Theory is if one knows all but nothing works. Practice is if all works and nobody knows why."[/i]

So I had this challenge idea. Christopher doesn't want to get in the act - OK, that's his decision. I'll nevertheless try to do some Theremaths although it is almost 20 years ago that I earned my maths diploma. In the best case we will get some formulas which might be helpful for future theremin designing. In the worst case I'll have wasted my rare spare time and will have to admit that there were more things between heavens and earth that I can actually imagine.

Now who's getting metaphysical? ;-)

To get back on topic briefly....

If the light organ might interfere with the theremin circuitry...could it not be a remote unit feeding LED's in the theremin or perhaps internally thru light guides (optical fiber)?

I will be doing the led expermiments, I'm only 2 weeks into building a Theremax at the same time I'm starting on the upgrade to a Lev antenna. See the spring and clear pvc pipe assembly here:
http://www.flickr.com/photos/15226899@N07/
I'm picturing the short nipple of pvc going through a hole in the side of the cabinet. The antenna tuning circuit (coil and trimmer cap) will be mounted on perf board on the inside of the right cabinet side. The feed from the tuner to the bottom of the spring will be RG-174/U coax.
I imagine the LEDs butted up against the wall of the cut end of the clear pvc nipple inside the cabinet. LED ckt mounted on the inside of the back wall of the cabinet, right close to where the power will come in. The whole mess will be removable in case it does cause interference.
First, I gotta polish up the cut ends of the pipe and see how much light the pvc pipe will transmit, and if enough light will follow the 90 degree elbow. If that don't work, the antenna already looks very cool and futuristic.

I know this is your project snuffy406 but I am getting excited so I thought I would throw some ideas out there. First, you have that entire extra piece plastic pipe; you should make the main clear tube an extra 6” or slightly longer to place the antenna spring further from the antenna LC tuning board. There is an interesting unwanted interaction between them. Also at the base of the main clear tube you could possibly cut slots for the LED’s to mount pointing upward through the wall of the main clear tube which slides down into the elbow. This keeps all your thin connecting wires and LED’s concealed in the elbow. Don’t forget that these LED connecting wires need RF isolation so don’t connect anything to or near them until you do the main theremin tuning to understand this affect.

With the elbow sliding through a hole into the side of your case you could have a third brass screw just above the elbow slide into the case above the elbow to make the mounting secure.

Also first use the PAiA regular antenna method of the kit to feel what the marvel of perfect linearity does when you switch over. Even the voice of the theremin will improve. Theremin antenna behavior exists from the pc board to the tip of the antenna.

Adding the Lev Antenna combination will shift the pitch oscillator frequency lower (the actual pitch higher) so you will need to back out the L1 coil slug somewhat to compensate, this is where I recommend using the AM radio for tuning. This is all found on that cluttered webpage, that needs reorganizing, yet as things go other awesome theremin projects currently take the front seat. Some theremin designs may not have the RF coil slug tuning range to adjust to the Lev Antenna so for experienced electronic builders who know how to compensate for this, they might add a few extra capacitor pico-farads to the opposite fixed oscillator tuned circuit. Never use variable capacitors other than the antenna LC because they will add to thermal pitch drift.

My Ultermen 5 revealed a method of octave sliding a few years ago and at the top of that Lev Antenna (http://www.oldtemecula.com/theremin/ult_antenna/index2.htm) webpage “Simplicity” reveals a future method of accurate real time theremin musical note popping.

[b]snuffy406[/b] your own Email address is obvious to you at Theremin World but not available to the public, so email me from my website someday. You are a pioneer and your success is important to me and you know who. ;-0

That was a lot of writing; I better check my blood sugar level! ‘)

Christopher
.

Most of you are way ahead of me on the experimental stage, but from what I can see so far, the nature of the beast is that you can only get musically-useful results empirically. You can't just "design them in".

Theremins remind me of the "old days" of "tuned wiring" (i.e. "lead dress"), where positioning of the wiring was every bit as important as the circuit design. In a theremin everything seems to interact with everything else. And in many respects that is exactly what creates the desired timbre.

You can certainly design very stable, non-interacting oscillator circuits, but the end result might be very "sterile" or "tinny" sounding. And while you can add effects after the audio, it is still a "garbage-in, garbage-out" situation. While this might be very frustrating, it is also part of the fun ... to see what affects what and to work with something that is "raw". You get to play luthier without having to be a master wood craftsman. Stadivarius didn't have a spectrum analyzer :)

Don