MIKE ROSS wrote to Martin Ridgley <=-

The basic principle of the theremin is that of beating (sum and
difference frequencies) between two radio frequency oscillators.

<snipped and saved>

Hope this wasn't too long an explanation...

Well, it probably falls under the heading of 'more information than
I really needed to know', but I've been casually interested in the
Theremin for some years now. I've even considered buying, or building
one on occasion, so I found this quite fascinating.

Thanks...

Martin
~~~~~~~~

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"Martin Ridgley" wrote to "Mike Ross" (09 Nov 00 14:52:06)
--- on the topic of "Re: Theremin"

Well, it probably falls under the heading of 'more information than
I really needed to know', but I've been casually interested in the Theremin for some years now. I've even considered buying, or
building one on occasion, so I found this quite fascinating.

Thanks...

I found a DXF of a very well designed theremin circuit but I also found
in my archives this simple experimental circuit you can toy around with.
Mind that it's not a very good theremin. It is basically educational in
nature, really just to show the working principles.

Theremin

Circuit diagram for a Theremin : the only musical instrument in the world
(at its time) that could be played without touching it.

Invented in the 1920's, by Dr. Leon Theremin.

Peter Knight p.j.knight@uk.ac.bradford

Theremin schematic

From the book
'103 Simple Transistor Projects' by Tom Kneitel, pp98-99
Published by Rider, 1964

This schematic is based on a post to sci.electronics by jmichael@vnet.ibm.com Schematic graphic by p.j.knight@bradford.ac.uk

All transistors are PNP

S1
__ Q1
9V-- --e c-------------------------------.
b ! !
! Q2 e---. \!/ Q3 e---. \!/
! ! ! Ant1 ! ! Ant2
! .---b C1 ! .---b C2 !
! ! ! ! ! ! !
R1 .-. c--+++--- .-. c--+++---
! ! ! ! ! ! ! ! !
! R2 C5 C3 L1 R3 C6 C4 L2
! !_! !_! !_! !_!
! ! ! ! ! 0V-------+----+---------+-----------+---------'

Q1 2N1097
Q2,3 2N1264

R1 180K
R2-3 51K

C1,2 200pF
C3,4 200pF Trimmer
C5,6 0.01uF

L1,2 vari loopstick

S1 SPST

Connections to the collectors of Q2,3 are made via 5 way binding posts. Antennas are Lafayette F343 whips.
Keep leads short. Cut shield connectors off 2N1264's. Place near AM radio Adjust 200pf cap at J1 until hissing noise, then 200pf at J2 for whistle, then back to 200pf at J2 for lowest pitch. Play with hands. Perhaps an
ascii artist can draw from the description. Good luck.

... Mad at your neighbor? Buy his kid a drum!
--- Blue Wave/DOS v2.30
* Origin: Juxtaposition BBS, Telnet:juxtaposition.dynip.com (1:167/133)

From the book
'103 Simple Transistor Projects' by Tom Kneitel, pp98-99
Published by Rider, 1964

Antennas are Lafayette F343 whips.

Ahh, that explains it. When I saw the above line, I was thinking "??!!??". Lafayette ("Lafayette Radio Electronics", actually) has been out of business since probably 1975 or possibly earlier. I used to get parts there when I was a kid, and still have a great old power amp from them which is labled "Knight",
which is their brand name.

Funny to see them mentioned anywhere again. Olsen Electronics was another chain that faded away about the same time, and were pretty much identical to Lafayette. (And another that I used to spend a lot of time in.)

--gary

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"Gary Gilmore" wrote to "Mike Ross" (10 Nov 00 11:36:50)
--- on the topic of "Re: Theremin"

Antennas are Lafayette F343 whips.

Ahh, that explains it. When I saw the above line, I was thinking "??!!??". Lafayette ("Lafayette Radio Electronics", actually) has
been out of business since probably 1975 or possibly earlier. I used
to get parts there when I was a kid, and still have a great old power
amp from them which is labled "Knight", which is their brand name.
Funny to see them mentioned anywhere again. Olsen Electronics was
another chain that faded away about the same time, and were pretty
much identical to Lafayette. (And another that I used to spend a lot
of time in.)
--gary

A lot of those great old stores are now gone. We had a similar one here
in Montreal called Payette Radio Ltd. Anyways, downtown there was all this gorgeous WWII surplus radio equipment in the storefronts of the radio strip
and the geewiz ham radio receivers with all the gizmos. Now it's mostly in these industrial area joints with $50 or $100 minimum purchases. Bummer...

... High Voltage Electronics: Life's a glitch, then you fry.
--- Blue Wave/DOS v2.30
* Origin: Juxtaposition BBS, Telnet:juxtaposition.dynip.com (1:167/133)

MIKE ROSS wrote to Martin Ridgley <=-

I found a DXF of a very well designed theremin circuit but I
also found in my archives this simple experimental circuit you
can toy around with. Mind that it's not a very good theremin.
It is basically educational in nature, really just to show the
working principles.

<snipped and saved>

Thanks Mike. I'm not very knowledgeable about electronics, but I
might just get a decent set of plans and have a go at building one
of these things one day. Hmmm.... come to think of it, it might
make an interesting project for my girlfriend, who's currently
studying to be an electrician. ;-)

Martin
~~~~~~~~

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Gary, any items that can't be obtained at a nearby Lafayette store can easily be found at your local Heathlit, Hallicrafters, or Allied store
:) Hope this helps........hehehe (couldn't resist)

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Oh man..I'd love to be find (an affordable) WW2 SWR :) Seems as tho the Zenith
Transoceanics are about the nicest portable, (yet affordable) receivers out there. Of course I've also heard decent reviews about the Japan Radio receivers
:( Anyway, I've heard decent
things about the Wards Airline guitar amps too. Any of you have the
odious priveldge of Playing a Lafayette Radio e;ectronics guitar thru a Heath 2x12 40 watt amp ? YEECH

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Lafayette store can easily be found at your local
Heathlit, Hallicrafters, or Allied store

Never went to a Hallicrafters store, but certainly have been to Allied and Heathkit stores in the past. I remember going to the Heathkit store and seeing
the guitar amp kit, and lusting over it. It looked like a Fender Twin.

--gary

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Gary,
I remember (years ago) going into the Heathkit stores, and wondering why a "kit" would in so many cases, cost more than the assembled product. Heathkit wasn't cheap, yet some of their "Ham" stuff was decent. I never had the interest in assembling (or the interest in trying). Lafayette, (where I got my first SW receiver...Starfire VI also had lot's of fun toys...Do you recall in the late 60's/early 70's the CB radio's they'd sell you w/o the microphone since you needed to be licensed to use one ? I wasn't yet 18, and back than CB radio's, and talkies (over 100MW) were taboo. SO of course we used to get on channel 9...and threaten "React"...hehe.

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