Well, welcome to the party... did you bring the drinks???
The "EM" Theremin is from the Electronic Musician magazine and the "EW" Theremin is the standard... Both designs were written and designed by Bob Moog....
The "EM" theremin was produced before the "EW" Theremin and therefore the 100uH and the 68uH inductors were more readily available. Because of these becoming obsolete, the 100uH and 68uH were changed to 47uH inductors and a fixed inductor was put in series with it to compensate for the original values. Thus the 47uH in series with a 47uH would give you 94uH... and the 47uH in series with the 22uH would give you 69uH.
The oscillator for the pitch is roughly 250KHz and the Volume is roughly 450KHz. With the way that the "antennas" work, (really capacitor plates), is that a small change in capacitance at the antenna makes a large change in the oscillator circuit.
The "Q" or quiescent of the inductors is nice to have them as high as possible, but from the fiddling that I have done with different coils in the circuit, the oscillators will still function correctly without any "real" noticeable differences. The main difference with the "EM" inductors compared to the "EW" inductors is that there is a bit less tuning area with the "EW" Theremin due to the fixed inductors. As this does NOT hinder the Theremin from operating correctly. The choice is up to you on which Theremin you want to build.
The capacitor changes, without going into a brain buster for most people... (Changing from the Time Domain back to the S domain and so fourth... and without doing a total mesh or nodal analysis on the whole thing),... kinda take up the "slack" for the difference in the inductors... yes.
As with any circuit, changing one or adding one part to a circuit changes the whole circuits characteristics. even a little bit, one might not think so, but it does... especially with RF designs.
I hope that I didn't ramble on to much and scare you off into not building one.... I have the "EM" Theremin working, with the original TOKO inductors and it's sweet... but there again, I am the type of person who has to build the others just because I can... :)
The biggest part about the capacitor plates is that they have to be with in the resonant frequency to work... the volume antenna will tell on you if you are to large,(Hand capacitance is roughly only 1pF)... if it is to large, you just won't hear anything... The volume oscillator will just be muted.
Also on another note... IF and WHEN you build it, start off with a couple of pieces of wire about 6 inches long for the antennas... this will make it much easier to know if you have constructed the Theremin correctly....
Hope this book helps out your question....
Don't forget to bring the drinks next time!
I forgot to address your last question...
A 66uH inductor theoretically will work, but there again, for the circuit to operate "properly", you will have to do an analysis of the oscillator circuits and change the capacitor values accordingly.
When building and modifying RF designs, you are playing with their resonant frequencies (inductors / capacitors) This type of circuit is an LC network and to stay within the same oscillating frequency range as the original design, you will have to:
a) Stay with the original design and part values
b) Use the "EW" circuit
c) Do a complete analysis of the circuit (From antenna through Volume or Pitch oscillator)
d) Trial and Error
Please note, I am not in anyway, shape, or form, trying to discourage you in building one. When it comes to modifications, there are a lot of different avenues that have to be considered.
In theory a circuit should or shouldn't work... that's the bottom line. Theory is NOT always right! Trial and error ALWAYS proves the hypothesis. Although... sometimes it tends to let the smoke out of the parts.
Hope this helps...
It is very important to choose L and C so, that the free-run frequency may be adjusted to 285kHz for best linearity, since the linearization circuit's series resonant frequency is fixed by the static antenna capacitance and the total 40mH of the 3 linearization coils and their parasitic capacitances.
Sorry for writing so short but I just returned from the hospital and have tons of steel, screws and plaster in and around my leg. Hope I'll be in a better mood tomorrow.
My response about "Q" was regarding Eddie calling it "quiescent of an inductor" ... probably confusing q-point of transistor bias with Q factor of an inductor.
The jury's not out on the effect of bandwidth though. It might be that having less sharp of a Q in your fixed oscillator gives you more range. So far I don't have direct proof on that yet, though.
Not a problem.. I was extremely tired last night when I typed the book... Yes, the "Q" being quality...
Thierry, Sorry to hear about all the hardware... That's gotta hurt!
Thierry is correct though.. this oscillator design will oscillate with just about anything wound as the inductor. To stay within the frequency range though, the change of inductance requires a change in capacitance.
Sorry for the mis-type on the "Q" factor....
Thanks Don for pointing this out...
For now, i've decided to stick with the EM oscillators as a unit, assuming i can get ahold of those coils from the UK. If not, then i'll try my "plan B" inductors from Digikey. (I might try them anyway just for fun.)
It's great that there are helpful folks on here with more electronics know-how than i. (I'm mostly able to read and follow a schematic, but my theoretical undertanding is pretty spotty. But i'm learning more with each project, and from reading the posts here, which is part of the point afterall.)
Thierry, sorry to hear about your leg. Best wishes for a speedy recovery.
And Eddie, you'd better believe i'm bringing drinks!
Here's (http://www3.telus.net/ereiswig/current/2009th.htm) my construction photos, including a youtube link at the end. I'm extremely happy with the instrument, so thanks again everybody!
I am Chris from Quibis electronics, and note you have referred to EZ-1015, supplies of these are limited, and we understand an alternative could be EZ-1016L, but the question is how do we pull the frequency using the EZ-1016L, so we could offer this as an alternative and give people the appropriate advice on how to pull it. Do you have any ideas?
Chris for Quibis