theremax antennae help

Posted: 1/15/2006 12:47:14 AM
dmahar

From: CT USA

Joined: 1/15/2006

Hello -

I'm going to be purchasing the Theremax kit over the next couple weeks (minus the lectern case and antennae)and I'm curious: has anyone here built the Theremax using plates instead of brass/copper rods?

If going with plates, are any special mods required for the circuitry?

Thanks!

Danny



Posted: 1/15/2006 8:05:49 AM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Because of the increased size of the plates over the antennas, you may need to tune the circuit slightly differently to compensate.

The trick with plates, however, and the reason they're not very poopular these days, is that it's difficult to isolate them from each other. With antennas perpendicular to each other, moving your hand along the pitch antenna doesn't affect the volume antenna as much, and vice versa. With plates, as found on the Maestro Theremin (http://www.thereminworld.com/theremins.asp?m=24&t=29) for example, you can see how interacting with the pitch antenna would also affect the volume antenna.

I'm curious why you're interested in plates over traditional antennas. Is it for aesthetics/design, or are you building it for a special purpose?
Posted: 1/15/2006 7:28:19 PM
dmahar

From: CT USA

Joined: 1/15/2006

Hi Jason,

I was contemplating the plate idea - especially after seeing a photo of one design at Art Harrison's site - quite simply because it appears to me to be a more comfortable set-up if sitting down to play the instrument rather than standing (as I prefer to do with other instruments, like my guitar and keyboard, especially when recording).

I'm no expert, but the plates in that "Maestro" design seem way too close to each other. Do you think any interference between pitch and volume "plates" for a possible design would be resolved if setting the plates further apart (15 to 18 inches), along the lines as I've read elsewhere here for the rods on the RCA and Etherwave?

Thank you.

Danny




Posted: 1/19/2006 9:29:46 AM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

That might help. Another possibility is to follow the design of the old Moog theremin and use a plate for the volume antenna but a rod for the pitch antenna.
Posted: 1/27/2006 2:14:07 PM
dmahar

From: CT USA

Joined: 1/15/2006

Hi Jason,

Like the old Moog Melodia? That does seem to be a sensible compromise, using a plate for volume and a rod for pitch.

I must confess, after reviewing all the material on the internet concerning antennaes, as to now having reservations about using a plate for pitch, due to issues concerning linearity.

I just ordered an old wooden breadbox off Ebay to house my Theremax - its shape seemed somewhat reminiscient of an poor man's RCA(lol).

The coolest enclosure I've come across so far on the net was a 1950s toaster (lol).

Danny

Posted: 2/11/2006 10:07:16 PM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Sounds like fun!! Send us pictures or post them here once you get your theremin stuffed inside the bread box. Did you decide to go with plates or rods?
Posted: 2/11/2006 10:35:22 PM
dmahar

From: CT USA

Joined: 1/15/2006

3/8 solid brass rod (sold as "curtain rods").
The loop antenna is going to be interesting to bend. If anything, I may pay a little visit to the machine shop at my daughter's technical school to offer the kids a little bending/threading project. :)

Danny
Posted: 2/14/2006 4:18:03 AM
dmahar

From: CT USA

Joined: 1/15/2006

As I await my kit to (finally)arrive in the mail this week, I'm curious - has anyone here actually tried hooking up in series 4 small inductor coils (10 uH ea.)to the pitch antenna of the Theremax along the same lines as Moog had done with his Etherwave design? I imagine it would be easy enough to try on a perfboard, connected and postioned between the pcb and the pitch antenna.
It would be interesting to learn what experiences people had here with such attempts.

Danny
Posted: 2/16/2006 11:54:50 AM
Jason

From: Sammamish, Washington

Joined: 2/13/2005

Check out the Lev antenna:

http://www.oldtemecula.com/theremin
Posted: 3/25/2006 12:14:14 PM
Etherdave

Joined: 2/21/2005

It took a whole afternoon to bend a 1/4" brass rod around my floor support pole in the basement. I can't even imagine the force required to bend 3/8". I suppose if one uses a long enough piece of rod the job could be accomplished in this manner, but anything else and you'll be needing a circular metal bender and some jigs. My old high school had the equipment, so I imagine it's not too hard to find.

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