Volume antenna spacing

Posted: 6/9/2013 5:50:09 PM
CHILDISHGAMBINO

Joined: 6/9/2013

Hi, I'm building an Etherwave and I'm wondering if the 3 and 1/4 inch spacing between either end of the volume loop is crucial.  I'm planning to house it in a cigar box that has two holes already drilled that are 3 and 1/2 inches center to center is this going to make a big difference or is it o.k?  Thanks.

Posted: 6/9/2013 9:29:01 PM
FredM

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'm wondering if the 3 and 1/4 inch spacing between either end of the volume loop is crucial. " -CG

I dont see any reason why it should be of any importance. The critical thing is the distance between pitch and volume antennas, and the length / diameter of the antennas.

Oh, and welcome to TW, CG.

Fred.

Posted: 6/10/2013 1:07:59 AM
CHILDISHGAMBINO

Joined: 6/9/2013

Thanks for the answer and the welcome.  I didn't think it would matter much but I didn't want to start messing with drilling holes in my enclosure if they weren't going to work.  Thanks again.

Posted: 6/10/2013 4:16:16 AM
FredM

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

 CG .. If you delete the above faulty links / posts, that will keep things tidy.

I simply used the automated image insert on the editor.. down at the bottom of the editor is a green icon, looks like a tree or something.. Simply click on that and enter the full URL for the image you want to paste..

You get this URL from right-clicking on the image and selecting "properties" .. then copy the URL.. for example, this was pasted into the URL of the image insert icon..

http://i4.photobucket.com/albums/y144/childishgambion/IMG_7178.jpg

The image is a bit over-sized, but doesnt need correction as everything is shown.

Personal taste ? (!) .. I dont like your box at all.. Your layout, on the other hand, looks real tidy!

Fred.

 

 

 

Posted: 6/10/2013 2:19:31 PM
CHILDISHGAMBINO

Joined: 6/9/2013

Thanks Fred.  This box wasn't my first choice.  I was planning on building a box from an old oak coffee table top but when I removed the top I realized that it was quite warped and I couldn't find about 75% of the tools I would need to build a box (I've moved a few times recently and stuff is all over the place).  I found this old cigar box that a friend did the creepy artwork on and it seem to be a perfect fit.  I'm going to drill little holes in the bears eyes so the surface mount LEDs can shine through.

Posted: 6/10/2013 8:49:00 PM
dewster

From: Northern NJ, USA

Joined: 2/17/2012

I like the creepy artwork!  But that big honkering AC transformer smack dab in the middle of all the exquisitely sensitive circuitry might give you some trouble, if only from the heat it will probably give off.

Posted: 6/10/2013 11:18:09 PM
FredM

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

" But that big honkering AC transformer smack dab in the middle of all the exquisitely sensitive circuitry might give you some trouble, if only from the heat it will probably give off." - Dewster

You are absolutely right.. I am getting lazy - I never even noticed it! ;-)

Fred.

Posted: 6/10/2013 11:28:16 PM
FredM

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'm going to drill little holes in the bears eyes so the surface mount LEDs can shine through." - CG

It must just be me - Horror isnt my "thing" at all - And combined with a musical instrument, well.. each to their own taste I suppose..

I really like the look of the RCA and the E-Vox, and the old wood-ended keyboards and synths.. And the wooden cased Moog Modulars, and the EMS Synth - Yeah, plenty of tech stuff, and loads which has an industrial look to it - but nothing which looks like it comes from some voodoo temple.. A plain cigar box with a couple of knobs on it would be much more appealing to me .. Even a plastic lunch box would be more appealing..

But stuffed badgers and creepy "bears" IMO just add more "novelty" to an instrument allready too dependant on novelty.

;-)

Fred.

Posted: 6/11/2013 3:19:38 PM
ILYA

From: Theremin Motherland

Joined: 11/13/2005

dewster: "But that big honkering AC transformer smack dab in the middle of all the exquisitely sensitive circuitry might give you some trouble, if only from the heat it will probably give off."

If transformer was designed with a reduced turns-per-1volt ratio, it has the significant external magnetic field that is not good for the ferrite based coils. 


Posted: 6/11/2013 3:44:22 PM
FredM

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

IMO, try it... If you get problems, its easy enough to remove the transformer and put this into a seperate box (one can get specific boxes like this quite cheaply):

Yeah, what you have done is certainly not optimum - even for something like an audio amplifier - let alone a theremin... And going for a torroidial transformer with contained fields is IMO always well worth the extra cost..

But its there - no point fixing something which might not need fixing ..

If you were really stuck, get some magnetite powder (or even ferric oxide - but magnetite is much better) and mix this with a silicon sealant - as much magnetite as you can get into the mix - then encapsulate the transformer in this... This really does reduce radiated magnetic fields (Many thanks to RoyP for advising me when I asked for advice on this idea - Being a chemist, I thought he might be good for advice - He was! ;-)

I have NOT tried this with mains transformers - I have only used it for shielding enclosures containing magnetic field sensitive components - So BEWARE of any heating effects and other possible hazards! 

Also - the magnetite paste will change the inductance of any coils it is placed over or close to, and it is probably a really bad idea to do this! - but a coating of a few mm painted on the inside of a theremin enclosure, or mixed with epoxy to form magnetic shielding strips / sheets - well, it works nearly as well as Mu metal as far as I can see..

Fred.

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