Need coils for em theremin

Posted: 2/29/2012 9:55:51 PM
Insanex

Joined: 1/27/2012

hello, i started to build EM theremin and i cant find these parts
10 mH, 3-section, RIF choke (J. W. Miller #6306)                                        2.5 mH, 3-section, RIF choke (J. W. M i ller #6302)
5 mH, 3-section, RF choke (J. W. Miller #6304)
Could someone suggest any replacments?

At farrnel.com i found this:

BOURNS JW MILLER - 70F102AI-RC - CHOKE, 10MH, 38MA, 10%, 520KHZ,Self Resonant Frequency: 520kHz

Its very har these days to find parts from this artical of building em theremin

Posted: 2/29/2012 11:05:10 PM
Chobbs

From: Brooklyn,NY

Joined: 12/1/2009

Miller 6300 series @ mouser

5mH is 6304:           http://www.mouser.com/ProductDetail/Bourns/6304-RC/?qs=VO2%2fVXZcKR17pYWmXVHtZg%3d%3d

10mH  is 6306:     http://www.mouser.com/ProductDetail/Bourns/6306-RC/?qs=sGAEpiMZZMueR%252blcXtRMwX8lj5SnzEMncTsxETOh8z0%3d

Posted: 4/5/2012 11:08:34 PM
Insanex

Joined: 1/27/2012

Hello

I was wandering about making air coils for em theremin, but not big, but 8 coils same as in schematic.

I am talking about to make 2.5mh ai coil other coils for antenas will also be air coils.

So the quiestion is will theremin work with that kind of coils?

Posted: 4/7/2012 11:35:10 PM
Chobbs

From: Brooklyn,NY

Joined: 12/1/2009

Dont make four 10mH seperate coils for the pitch-  Wind one coil with a value equal to the sum of the listed parts' value.   pitch is 40mh ,Volume will be 12.5 mH  + 2.5 mh (use the miller choke for this one)  Happy winding.

 

Posted: 4/8/2012 7:29:42 PM
Thierry

From: Colmar, France

Joined: 12/31/2007

I fear that air wound coils with the same inductance will have much mure parasitic capacitance and thus a lower SRF which risks to either reduce the pitch range and/or to compress the pitch field near the antenna more than coils with a higher SRF would do. That's why I would go with 3  to 4* of the Miller 6306 or even better the Hammond 1535G (730kHz SRF) coils. Both are 10mH 3-pi wound in order to reduce stray capacitance. 

*with a 10mm(3/8") thick and 40cm(16") long pitch rod, 3 will be enough. 4 will be needed with a thinner and/or shorter antenna.

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