Antennas & antenna coils for EM theremin

- copper is very soft so you may want to consider filling the tube with epoxy (as per the EM article) after bending to prevent it from getting messed up.

Is really that necessary? Anyone has experience using theremin with antennas not filled? It seems to me that copper tubes are rigid enough, not bend if theremin is handled with less or more care.

- copper is very soft so you may want to consider filling the tube with epoxy (as per the EM article) after bending to prevent it from getting messed up.

Is really that necessary? Anyone has experience using theremin with antennas not filled? It seems to me that copper tubes are rigid enough, not bend if theremin is handled with less or more care.

I dont think that you'll have much luck bending "hard" copper tube- like the stuff used for plumbing pipes.   The EM article assumes that you will be using the "soft" copper tube (usually sold coiled up- I think this is used for stuff like connecting ice makers and coolant.  )  Very easy to bend (and rebend), but can also easily be crushed or otherwise messed up by casual bumps and bangs.   Therefore, something non conductive(and with little capacitance) is necessary to strengthen it.  

Hi there,

In this day and age when volume circuits can be extremely sensitive why a loop for the design? 

A straight sturdy chrome pipe 25 mm dia, 4 cm long  can work quite effectively allowing for less response near the open end. Is the desire for a loop more cosmetic or to aid in a less responsive volume circuit?

Silvered Mylar tape is also very electrically responsive so a more sculptured volume control design is possible.  You could coil mirrored 1/2" transparent plastic, embed a wire in a wooden cane, has personal creativity fallen by the wayside? I appear to be going way off thread. Stop the Replicants! oops

I have researched and redesigned my own volume control a lot the past year. My goal is a volume control separated from the pitch section so it can be placed anywhere around me for comfortable play. This solves the problem of right or left handed theremins, makes a pitch only a true theremin and it even has a switch to reverse the response direction on the spot without any retuning. Some Thereminist find the non-standard hand response direction to be more intuitive. Add wonderful shading in the quiet range, a mute switch, a pitch preview and you have what might be a revolution in theremin design. Stop pretending you have a classic when you never will and strive for your own ideal sound with control.

I have thought about the need of an independent volume control for years. It is not a gadget I sell, but a design given to the DIY'er to build, if they understand basic electronics.

Christopher

Couldnt you, theoretically,  just anneal the plumbing pipe with a torch, to make it soft enough to bend into shape? It might take 2 annealings, but that would solve the problem. As would work hardening the soft thinner copper tubing. Seems more elegant than filling with epoxy. 

Couldnt you, theoretically,  just anneal the plumbing pipe with a torch, to make it soft enough to bend into shape? It might take 2 annealings, but that would solve the problem. As would work hardening the soft thinner copper tubing. Seems more elegant than filling with epoxy. 

Now that's I think is elegant indeed!

The EM article assumes that you will be using the "soft" copper tube (usually sold coiled up- I think this is used for stuff like connecting ice makers and coolant.  )  Very easy to bend  

Didn't know coppers can be different. It seems that tube I have is quite rigid one (12 mm outer diameter). Of course it's possible to bend it with bare hands but it's not as easy as Chobbs describes.

Also, my tube is not chrome finished - just copper which easily oxidates which make it look not very good. I plan sanding it and covering with a lacquer. But can't lacquer's properties influence antenna's capacitance significantly?

If you dont coat it with lacquer, for whatever reason, oxidation can be cleaned off easily with a mixture of vinegar and salt, once every 6 months or so.

"Is the desire for a loop more cosmetic or to aid in a less responsive volume circuit?"

I dont know, Christopher - I think it probably has more to do with what people are accustomed to - Lev's theremin was the "template" .. And, regardless of functionality or otherwise, people regard the volume loop as "authentic".

I entirely agree with your ideas on this matter - I have never made a loop antenna - just too much damn effort without any benefit (a bit like large air coils!) - I have used aluminium tape over whatever former I wanted to use..

But, in all probability, if I get theremins to market, I will need to waste money on getting someone to produce loop antennas for these theremins - Simply because people wont buy them if it doesnt have a loop!

(it is interesting to see how Bob Moog never bothered with a loop in his earlier theremins - he used the much simpler plate antenna )

Fred.

The loop could just be ergonomics as well, as it has a large surface area, and is easy to rest the hand in without looking. When playing with other people, not playing on every passage of a song, i would think especially, over just articulation, but it could be just what im used to. A straight antenna would seem, theoretically, slightly awkward.   

A straight antenna would seem, theoretically, slightly awkward.

Not if you could adapt it to any place you stood or sat and at any height.

I would always recommend some sort of insulation coating on the volume loop for several protective reasons. Three immediate thoughts are protecting the metal, shielding from static discharge and the fact that some volume circuit designs react poorly to the loading affect of direct contact, your sound could come back on.

If you try annealing the pipe, before bending you will then need cap off an end, then pack it full of fine sand- then seal off the other end.  This will prevent the tube from collapsing.  -Also dont bother with anything thinner than .065" wall.   98% of the time it will collapse- brass at least, never messed with copper.   Its good to make a jig to aid in bending.

making a "proper" loop isnt that hard- decent mounting hardware on the other hand is a real PIA