Lev's Antenna for the New Millennium

Just for you, Thierry (by the way, does this rhyme with theory?):

http://esl.eng.ohio-state.edu/~volakisw/
volakispdfs/2002Journal/
AntennaModelingTechniques_Volakis.pdf

sorry for the long link.

Don

Personally all that vector calculus gives me a headache, but it looks like others have taken the time to analyze all sorts of new antenna shapes.

Don

Don, thank you for the link. I'll print this comprehensive document out and read it during the weekend. Why do they always write in English? This takes 10 times more to read than in French or German... :-(

For the moment I'm not sure if the classical antenna theory (the antenna as resonant element adapted and adjusted for optimal radiation energy transfer) may really apply to the theremin.

I will first see if there isn't a pure capacitance (E vector only) based model which fits easier to the theremin. If the standard antenna theory would apply, a 260 meter dipole would give best results on the Etherwave Standard... *whistle*

Well you can affect a theremin from 8 feet away (the one I've been playing with, anyway), so I don't think capacitance is the only thing affected.

It's more like you, the thereminist, become a "RF brick wall", reflecting some energy, absorbing some energy and detuning the oscillators in the process. "RF reverb" :)

When you stick your hand inside the instrument, that's probably closer to pure capacitive reactance effects.

Don

I will not start a discussion about probabilities in this moment. I hope to see this in a few weeks with my equations.
BTW: The question of distance is relative. At 8 feet distance you have just half the capacity as you would have at 4 feet. Theoretically you may use the capacitive model for almost infinite distances. C = e x e0 x A / d. The questions I will have to answer are among others:
- May very small capacitance changes really de-tune the oscillator?
- What is the exact (predictible and calculable) effect of a coil (or still a more complex tuning circuit) in series with the antenna?

But I'll stop now these speculations and come back on this problem when I can give meat with the potatoes.

Thierry:

We need to consider the "media" as well as the antenna side. Just as multipath distortion can be a problem that causes TV ghosts and problems with FM stereo reception from an antenna, reflections off us (and anything near the theremin) can alter the frequency.

So the "load" (i.e. the thereminist) can impose a complex RC network for the theremin. There's probably not much of an inductance to worry about on the load side.

Don

Hi Guys, please excuse me from gate-crashing your conversation - Stradivarius DID have and use a spectrum analyser - he actually had two of them - better known of course as his ears! Cheers, Bebbspoke

If you have seen the documentary film, THEREMIN, AN ELECTRONIC ODYSSEY, you may have noticed that at one point in the first section of the movie, the late Bob Moog remarks that it is surprising that Leon Theremin was able to come up with the distinctive sound that his instruments had when you consider that he was using only his ears and did not have the luxury of modern oscilloscopes.

Curiously, although he tried, Bob Moog and his oscilloscopes were never able to duplicate the sound of Theremin's theremins.

The development of the sound we hear from Clara Rockmore's instrument, which many precision thereminists consider to be the gold standard, was the result of a collaboration of TWO sets of ears - Clara's and Lev's.

Nice one, Bebbspoke. And of course his spectrum analysers were directly connected to one of the most sophisticated computers known to mankind.

Welcome to Theremin World.



(Is that Bebbspoke as in "Bebbspoke Electronics Ltd"?)

Thierry ... it's long past your June deadline :)

The analogy of ears to spectrum analyzers is closer than you might think. The hair motions in your inner ear are coupled to groups of nerves ... these are bundled into groups (formants) that break things into spectrums instead of just every hair connected via its own nerve directly to the brain. Well that's what I read about it anyway.

As for the colored LED stuff ... there are LEDs with 3 elements inside (red, green, blue) and finally there are controller ICs available to drive them. So you could use a signal from the audio output of the theremin to drive the controller chip and display a different color for every frequency.

Don