Newbie question - greatly modify antenna shape?

Hello all,

I am researching the possibility of creating an interactive art project that would involve a Theremin. My goal, if it's possible, is to place a wire around the outer edge of the structure that would act as the antenna to vary the pitch. This would hopefully allow multiple people to interact simultaneously with it if they wish.

The overall shape of the wire will be round. Length about 15 - 20 feet. I'm thinking a pitch only circuit is fine for now. Also, since this will not be played in any formal manner, having a unit that is tuned or precise is not really a priority.

Is this possible?

Do I have to make sure that the structure surrounding the antenna is not metal?

I'm interested in a kit or a basic DIY circuit. Is there one in particular that lends itself to this use?

I have worked with circuits, but am far from having an in-depth understanding of electrical engineering.

Thanks,

-SF

Welcome to theremin world. :-)

I'll answer the bit I can.

Any conductive object near the antenna will affect the field.

Here is carport888 using carbonated drinks to embiggen the field of an RCA Victor theremin quite cromulently.

http://www.youtube.com/watch?v=qmk2Hlwpl3s

One other thing.

[i]I'm thinking a pitch only circuit is fine for now.[/i]

The raw sound of a theremin, without variation in volume or timbre and played aleatorically, is hard on the ear, even for a theremin nut like myself. I'm thinking your audience might find its own way of varying the volume, by walking [i]away[/i] from it.

If you have not already done so, I would invite you to consider some means of varying the volume and possibly also timbre over time, either through audience interaction or algorithmically.

(I would also add, as a thereminist with a somewhat aleatoric playing style, that delays can add a lot to the depth and richness of the sound.)

Hello SF,

Your project would bring a smile to Lev Termen. Most of his research expanded beyond what people recognize as his main work, the musical instrument. Some people only see him through his tube/valve designs, but trust me; he used transistors and the collection of components modern electronic hobbyist use today, right up until his in death in 1993.

I also study the theremin principles more as Art than a “static” musical instrument, the only musical instrument played without contact or moving parts!”

In a museum display the most effective response is when the theremin un-mutes and rumbles low to {{{shake}}} the ground when someone enters the pitch field, this draws their attention and can be up to eight feet away. Then steadily the pitch rises as the subject moves in for a closer look. Maintaining the Physics of this affect is no easy task!

Carport888 is brilliant in his many honest demonstrations of raw theremin behavior. In Gordon’s video, carport888 is demonstrating the real problem with museum theremin displays.

How do you keep the instrument precisely tuned in a changing environment?

The paradox of simple real theremin design is . . . there is nothing simple about it. Only a handful of us at TW can truly understand what this means.

Frequency or pitch drift is one of the main obstacles of theremin control. This is the issue Paul Tanner tried to overcome with his instrument he called “The Box”. His instrument brought more recognition to the theremin than anything had before it. I find it interesting that so many talented people can spend there time finding the flaw to bash creativity for what it isn’t, rather than have the enlightenment to recognize or complement genius in the “rare moments” that it reveals itself.

Christopher
.

Gordon>>
You cannot even begin to imagine how much the word "embiggen" has had me searching through the dusty labyrinths of my cranium, trying to remember where I last saw the word. I eventually located a reference at the back of a small filing cabinet in the Obscure-Words Oubliette, (13th synapse on the left along the Corpus Callosum). So, tell me ... am I right ... it's engraved on Jebediah's statue in Springfield? If so, I can stop the mental torture!

Any math freaks out there care to calculate the radiation resistance of full soda bottles? LOL Will there be a thread on grape soda vs orange soda as the best theremin tuner? Sorry, couldn't resist!

Carport888's demonstration was very interesting and insightful! As a wild guess, I would postulate that the soda bottles are dampening the pitch oscillator's tuned circuit. By so doing, it would naturally widen the bandwidth.

Don

Christopher - carport888's video, not mine.

Thereminstrel - I use google for stuff like that. Yes, you are right.

Don - or you could play match the drink to the thereminist - who might be bitter lemon, and who would be something a bit fruity? I'd be Irn Bru - it's a decidedly acquired taste. I think Pamelia would have to be Electric Kool-Aid.

Also, at Without Touch 2.0 one of the performers laid a softened and folded CD over the wooden arm of his ePro (Think of Dali's soft clocks (*) in The Persistence of Memory) to achieve the same effect.



(*) Imagine how carefully I typed that phrase. :-)

subliminalfringe -- Rather than spend hours, days (years?) researching this (yup ... guilty as charged!), buy one of the kits or finished theremins and experiment with different antennas.

The existing theremin designs have all the messy "engineering" aspects worked out for you. You will just have to do so tweaks to the tuning when you change the antenna. The math for antenna design is too messy to deal with, in my humble opinion (think Maxwell's equations, vector calculus and other things not so fun to deal with!), so make your antenna whatever shape you want and tune the theremin to work with it.

Don

Thank you all for your insight and comments. I'll try a kit and experiment with antenna configurations. I'll let you know the results and if my cunning plan comes to fruition, I'll post pics or a short video.

-SF