Hello, i would like to begin to learn theremin to understand if is an instrument that could be used with my band (surf music) in the live sessions.
I would like to begin with a cheap one kit (jaycar) to understand what kind of instrument i need and buy a pro intrument.
I read in this forum that there are several mods that can make the instrument more playable but the links on the thereminworld pages are dead.
I think that i'll build a bigger wooden case and better antennas.
could it be a good start instrument?
can you tell me the right antenna's size and material?
do you know the other mods that i can do to improve the sound and playability?
At first, you should get the kit working "as is" because if you immediately start "modding" it and a problem appears, it will be still more difficult to find its cause. That's why you should always proceed step by step.
Every later modification, be it different antennas, another cabinet, the addition of pitch and volume fine tuning knobs or even a skewing or timbre control will require a complete retuning of the internal variable inductors. Thus you should already be familiar with this procedure before applying the first mod.
There is a long list of suggested mods for this instrument by Dutch theater engineer Max Baars. Unfortunately these informations are actually not accessible via thereminworld.com (a bug in the new forum software?), so I allow exceptionally to point you towards another theremin website where you can find this. But take care: This has been written by an engineer for technicians. Never undertake a step if do not exactly understand what you do!
In the article which I linked, there is a diagram which shows the needed inductance of the coil, depending on the antenna's dimensions. This diagram starts from the point that you have already a decent antenna built with the circuit in a decent cabinet. It makes no sense to try to linearize this wobbly telescopic antenna in the plastic box.
After you have the antenna and the cabinet, read the needed inductance in the diagram. Don't try to wind it yourself since that will not give you precise results. You should rather order this set of 3-pi-wound inductors with low parasitic capacitance, 1 x 5mH (Hammond 1535D), 1 x 2.5mH (Hammond 1535B) and 3 x 1mH (Hammond 1534A), which will allow you to combine all relevant values from 7.5 to 10.5mH (the latter value will be required when you use the 10mm diameter, 40cm long pitch rod which I suggested before) by adding them in series (formulas apply as for resistors in series) in order to build the required value.
You should have enough space in your cabinet to put these coils not too close one from another in order to prevent coupling (see also the position of the linearization coils in a modern Etherwave theremin).
i would use a wooden case 47cm*20cm, i think that's is big enough to put the inductors 3 or 4 cm distant one from other at 90° to minimize interactions.
For the pitch antenna i could use a 40cm*10mm chromed copper hydraulic pipe but the graph in the page tell me that for that pipe i need a 10,6mH inductance, could that 0,1mH be significant?
"Hello, i would like to begin to learn theremin to understand if is an instrument that could be used with my band (surf music) in the live sessions."
I believe you can. In fact, it's already been done by a surf-rock group called 'The Manatees'. You can sample one of their CD's at CD Baby, however the theremin is only lightly used on the album and heard only briefly on two of the samples: 'Beyond the Wave' and 'Rolling to a Stop'. They do a nice cover of Gary Numan's 'Are Friends Electric'.