Very simple pocket theremin

Hi.
I never played theremin before but I'd like to make one in fact I need a small portable instrument.

http://www.geocities.com/SunsetStrip/Studio/2987/theremin.html
I found that thing. It makes a lot of noise but I think that can be easly fixed.

I have some questions about building my theremin:
1. Can I use telescope antenna (around 50 cm long, like guitar neck) and make it sense my body only when touched?
2. Is it possible to add acumulator and to charge it thru USB socket?
3. Can I make theremin sounds more like sax than old game console?

Regards.

[i]I have some questions about building my theremin[/i][b] This isn't a real theremin, only an oscillator which makes a theremin-like effect in junction with an AM radio[/b][i]:
1. Can I use telescope antenna (around 50 cm long, like guitar neck) [/i][b]YES[/b][i] and make it sense my body only when touched?[/i][b] NO, because it is the varying distance between the antenna and your body which varies the capacitance between plate/antenna and ground and results in different tones. Touching it will always produce the same note as long as you don't vary the tuning of the associated AM receiver.[/b][i]
2. Is it possible to add acumulator [/i][b]YES[/b][i] and to charge it thru USB socket? [/i][b]PERHAPS. This oscillator is designed to operate at 9V DC. The USB port gives only 5V, so you would have to check out if it still works at such low voltage.[/b][i]
3. Can I make theremin sounds more like sax than old game console?[/i][b] PERHAPS. This cheap experimental oscillator configuration does not have any wave shaping. So the sound will mostly depend on the AM radios sound quality.[/b]

You should be warned: This single oscillator - radio combination will not satisfy you. In your place I would consider building a real simple theremin with two oscillators and a mixer so that I would independent of such an instable device like an AM radio. Have a look here:
Click me (http://forums.audiofanzine.com/index,idtopic,311686,mao,un_theremin_simple_a_construire_et_qui_fontionne_.html)
(OK, it is in French, but there are detailed pictures and a PCB layout.)

Thanks for the link.
This theremin sound really nice (like professional one, from that I heard).

1. What would give me the second oscillator?
2. By mixer you mean high/mid/low frequences control?
3. If I can't touch the antenna, how can I make something like this: http://www.youtube.com/watch?v=xuRe_H1-Pe0 ?
I'm playing guitar so it would be a LOT more comfortable for me to play this way (but still I want be able to shorten the neck/antenna).

Hi Inq,

The theremin tone is made by taking two radio frequency sine waves at slightly different frequencies and heterodyning them. (Heterodyning is the radio name for ring-modding.) This creates two new waveforms mixed together - one the sum of the two frequencies, one the difference of the two frequencies, and then we filter out the higher of the frequencies. What remains, the difference or "beat frequency" - is the sound you hear.

In a theremin there are two radio frequency oscillators running at the same frequency, so the difference is zero - silence. BUT - one of the oscillators - the variable oscillator - is attached to some metal, usually shaped like an antenna, which acts as half of a capacitor. When the other half of the capacitor - your hand - approaches it the oscillator goes out of tune like a cheap radio, creating a slightly different frequency to the other - fixed - oscillator. Then heterodyne the two as above and Bob's your uncle. For different timbres apply filters and distortion etc.

You don't have to use an antenna to vary the frequency of the variable oscillator. You can use a ribbon controller - then you have the makings of a [i]theremin cello[/i] (a different beast to a [i]theremin[/i] but invented by the same guy - Lev Sergeivitch Termen AKA Léon Theremin - hence the similar name) as in the video you mentioned.

(Incidentally, the whammy bar is a volume control.)

At first - I'm really thankful for your fast anwsers. You helped me a lot already.

Moreover - although the ribbon controller seems to be simple in practice I can barely imagine how to make it work.

http://www.angelfire.com/music2/theanalogcottage/ribcont.htm

I have to put on a plastic neck a piece of some voltage conducting stuff (aluminium foil?) with 9 V voltage wired to it. Than I put foam (a piece cutt from a diving suite would serve well?). When the foam tight the foil/tape (is tape necessary?) it affects the pitch of sound?

And one other thing - do the lenght of the neck depends on the pitch of the sound (like the scale in normal instruments)?

Yes, the tape is necessary. The ribbon controller is just another sort of potentiometer. The video tape is like the carbon track in a sliding pot.

I think you would need stiff foam to stop it sagging in the middle. I think this design is only good for making a very short ribbon controller because of that.

With the battery attached you could use it to control a voltage controlled oscillator.

http://en.wikipedia.org/wiki/Synthesizer#Fingerboard

Can I use something covered with graphite spray instead of tape (there I have carbon as well).
It's electroconducting.

Isn't the battery in ribbon controller necessary? From that you said I understand it would give me just an extra feature.

The graphite spray will be too conductive. So you would have only a very small and very high pitch range. The battery (or whatever current source) is necessary to make the oscillator work.

[i]So you would have only a very small and very high pitch range.[/i]

Why?

Inq, I think it would benefit you to learn a little of the fundamentals of electronics before pursuing this project further. I foresee many, many more questions of this nature.