variable inductors and frequency in a theremin

Posted: 3/9/2006 4:37:11 AM

From: socal

Joined: 3/9/2006

I'm new to theremins. my dads friend gave me plans to build a transistor theremin (he's had the theremin since the 60's but did not build it). I got all the parts except for the tuning capacitor and the variable inductors at radio shack. Now here's the problem: Every electonics parts place I call tell me the numbers on the var. coils are not proper parts numbers but "house numbers"(?). They need to know the inductance and what frequency the coils operate at. My question is: how do I find out what frequency the coils operate at? His original theramin still works...Does anyone know how to test the coils to find the frequency?

Please help. I really want to build this theramin!

Thanks in advance for the help.
Posted: 3/23/2006 1:37:03 AM

Joined: 2/21/2005

As long as the two oscillators in each pair of oscillators (assuming your model is a dual-heterodyne design) contain the same parts the resulting frequency ranges don't matter much... as long as you can bypass the volume circuit temporarily you can tune the pitch oscillators, then tune the volume oscillators afterwards. If your tuned coils are designed for radio hobbying you have no worries.
Posted: 3/23/2006 2:07:07 AM

From: socal

Joined: 3/9/2006

Thanks Etherdave! I'll try that.
Posted: 3/23/2006 2:41:04 PM

Joined: 10/8/2005


Just for fun google the house numbers and see what you get. Sometimes a shot in the dark hits something you want to hit. Not having any idea what we are dealing with I would say take the inductors out of the board and have somebody with an inductance bridge measure them or give them the board. If you are desperate and it is reasonable to ship, I can measure them for you for the postage.


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