Eric,
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!
Eddie
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!
Eddie
