Pitch antenna: 1/4" rod, or ...?

Hi ho,

Ok, my first question. I've been reading lots of previous postings about pitch antennae, and it seems like lots of folks are using 3/8" tubing.

Right now the pitch rod on my Theremax is made of 1/4" solid copper rod, 14" long. Would there be any point in making a new antenna of 3/8" tube, or even 3/8" solid rod? Is there a performance difference between tube and solid? Are we talking surface area, or mass, or...?

(Both antennae on my theremin plug into standard 1/4" phone jacks. I've got a metalworking lathe, so it's no problem to make up the shape of a 1/4" phone plug on the end of whatever antenna.)

Be seeing you,

eric.

A longer and thicker rod will on one side pull your pitch range up since it has more static capacitance. This may be compensated on the theremax by adjusting the fixed pitch oscillator's coil (L2) slightly clockwise.

It will also show more capacitance variation for a given distance between two hand positions, so that the pitch span will increase within the same geometrical range, that means that tones will be closer together.

At the frequencies around 900kHz used in the theremax there will be no difference if you use a tube or a compact rod.

There is a pdf document from the Glasgow University dealing with theremin antenna questions. I created a download link for you:

Click me (http://dl.getdropbox.com/u/1548721/Theremin/Theremin_Am_J_Phys_excellent.pdf)