EM Theremin Antenas: Stainless steel?

Posted: 6/22/2017 6:34:36 PM
rob reido

Joined: 6/22/2017

Guys,

I am looking to build an EM theremin, as detailed here. I'm aware it recommends copper tubing, but for various reasons, 10mm solid stainless steel bar would be more convenient. Would this still work as antennae, or is the hollow nature of the copper piping instrumental to the theremin's functionality?

Thanks as lot.

Posted: 6/22/2017 6:59:19 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

Solid stainless rod, chromed hollow copper tube, aluminum tape over 3/8" PEX, it shouldn't make any difference.  The diameter and length are the main features that impact response.  Also, you might want to insulate it with some heat shrink tubing.

Posted: 6/22/2017 8:13:26 PM
oldtemecula

From: 60 Miles North of San Diego, CA

Joined: 10/1/2014

I agree with dew, he may not agree with me

Before you cut the Pitch rod know the length in conjunction with the antenna chokes forms a series tuned circuit that should be tuned to just below the Pitch Osc frequency. There are several reasons for this.

You can observe this tuning with the loose coupling of an oscilloscope probe near the rod and watch the RF voltage rise or fall as you tune the Pitch Osc. Increase the Pitch Osc frequency until the voltage peaks then starts to decline, this is where you want to be, you may even want the Pitch Osc a little higher in freq.

Static discharge is around 10kv, just don't touch the antenna.

Christopher

Posted: 6/22/2017 8:19:06 PM
rupertchappelle

Joined: 5/8/2017

What you probably want is a toilet inlet pipe - not the flexible kind like a hose, but the old style that is just a pipe of the right size for a theremin antenna.

It fits into the nut of an Etherwave perfectly and available at any hardware store, unless they have been rendered obsolete lately. You can trim them down to size or even have several different lengths.

You will need the compression fitting to keep it from falling out. The nut goes over that.

While anathema, a plate antenna is the easiest one to play.

For several years I used a copper wire coil, which could be tuned by stretching it out or compressing it. The best thing about the copper coil is that if you whack it, you have free vibrato as it swings back and forth. Before that, I used a coat hanger.

Capacitance doesn't care about style.

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