Wasn't theremin able to construct his instruments with junked radios, smashing the local oscillators together through a diode junction and low pass filter? How might I do this rather than go through the fabrication procedures of most schematics projects. I guess first off I would need access to a RF O-scope and a schematic archive for most radios on the market? If anyone has any advice let me know.
Theremins Techniques?
Posted: 6/6/2010 9:55:57 AM
From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................
Joined: 12/7/2007
There are a load of theory and construction articles, and spreadsheets etc at Element-14 Theremin General Resources (http://www.element-14.com/community/groups/theremin-general-resources?view=documents)
for basic tutorial on AM radio recievers see AM Radio Recievers (http://www.electronics-tutorials.com/receivers/am-radio-receivers.htm) - This site also has lots of useful data on IF transformers etc.
If you understand how Theremins work, you will understand how one could use old radios/parts to make them.. But, at such a time, you will realise that there is no point in doing this! Even the simplest dedicated Theremin circuit will surpass a theremin built using smashed-up radios - and will be a lot easier to build than bodging radios together.
As for the equipment you need.. A o'scope is extremely useful.. but one does not need a high spec 'scope for BASIC Theremin testing.. The oscillators will be running below 1MHz, and if one wants to view the waveshape of a 1MHz signal with reasonable quality you only need a bandwidth of 20MHz.. Most of the time you will be debugging signals after the mixer, where you would want to see a) That the HF components are filtered out b) The audio waveform has the shape you want / expect c) Other audio-side functions behave as expected d)Power supplies are clean etc..
A better 'scope will help you to trace more elusive bugs, like oscillations from supply regulators or opamps.
Oh, just for the record.. I doubt that Lev Termen used "junked" radios - LOL - Back in those days, Radios were not the sort of thing you found in junkyards.. they were probably about as rare as true 3D TV's are today!
for basic tutorial on AM radio recievers see AM Radio Recievers (http://www.electronics-tutorials.com/receivers/am-radio-receivers.htm) - This site also has lots of useful data on IF transformers etc.
If you understand how Theremins work, you will understand how one could use old radios/parts to make them.. But, at such a time, you will realise that there is no point in doing this! Even the simplest dedicated Theremin circuit will surpass a theremin built using smashed-up radios - and will be a lot easier to build than bodging radios together.
As for the equipment you need.. A o'scope is extremely useful.. but one does not need a high spec 'scope for BASIC Theremin testing.. The oscillators will be running below 1MHz, and if one wants to view the waveshape of a 1MHz signal with reasonable quality you only need a bandwidth of 20MHz.. Most of the time you will be debugging signals after the mixer, where you would want to see a) That the HF components are filtered out b) The audio waveform has the shape you want / expect c) Other audio-side functions behave as expected d)Power supplies are clean etc..
A better 'scope will help you to trace more elusive bugs, like oscillations from supply regulators or opamps.
Oh, just for the record.. I doubt that Lev Termen used "junked" radios - LOL - Back in those days, Radios were not the sort of thing you found in junkyards.. they were probably about as rare as true 3D TV's are today!
Posted: 6/6/2010 3:25:09 PM
[i]and will be a lot easier to build than bodging radios together[/i]
Although, if you want to bodge up a very crude device in about ten minutes, they really don't come any simpler than the homemade theremin using three radios (http://www.youtube.com/watch?v=PSYPUhPGavQ). (yT link)
[i]Back in those days, Radios were not the sort of thing you found in junkyards..[/i]
... and in about five years that's where every analogue radio in the UK (http://en.wikipedia.org/wiki/Digital_radio_in_the_United_Kingdom#Analogue_switch-off) will probably be.
I think that the circuit bending community will be as pleased as Punch, and making a lot of very crude thereminesque devices!
Although, if you want to bodge up a very crude device in about ten minutes, they really don't come any simpler than the homemade theremin using three radios (http://www.youtube.com/watch?v=PSYPUhPGavQ). (yT link)
[i]Back in those days, Radios were not the sort of thing you found in junkyards..[/i]
... and in about five years that's where every analogue radio in the UK (http://en.wikipedia.org/wiki/Digital_radio_in_the_United_Kingdom#Analogue_switch-off) will probably be.
I think that the circuit bending community will be as pleased as Punch, and making a lot of very crude thereminesque devices!
Posted: 6/6/2010 8:55:12 PM
From: Eastleigh, Hampshire, U.K. ................................... Fred Mundell. ................................... Electronics Engineer. (Primarily Analogue) .. CV Synths 1974-1980 .. Theremin developer 2007 to present .. soon to be Developing / Trading as WaveCrafter.com . ...................................
Joined: 12/7/2007
[i]"... and in about five years that's where every analogue radio in the UK will probably be." - GordonC [/i]
Yes - really sad that.. Its quite difficult to buy an AM radio these days - and loads of (FM)radios with many years of life left will be discarded.. so much for RoHS - all these units will be dumped en-mass adding to the toxicity along with all the TV's which are now useless..
I agree that some use will be made of this 'junk' by circuit benders and hobbyists - but this is not likely to produce anything remotely comparable (in terms of quality or playability) to even the cheapest Jaycar (SC) Theremin costing about £20 (kit).
Yes - really sad that.. Its quite difficult to buy an AM radio these days - and loads of (FM)radios with many years of life left will be discarded.. so much for RoHS - all these units will be dumped en-mass adding to the toxicity along with all the TV's which are now useless..
I agree that some use will be made of this 'junk' by circuit benders and hobbyists - but this is not likely to produce anything remotely comparable (in terms of quality or playability) to even the cheapest Jaycar (SC) Theremin costing about £20 (kit).
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