Re: Copper Banding?

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "david baehr" <dfb25@xxxxxxxxxxx>


 My orig. idea was, for the cap I want to use, I need to add a couple more 
turns on the pri. I like to keep the toroid OD a little larger than the 
pri. OD, and with adding a few more turns, its gonna start gettin' to big, 
and ,thought, going to a more compact ribbon type would help, but, from 
what your saying, although I'll save space, inductance will be lower 
anyway, so , stay with the copper tubing ??? The coil runs well, but Im 
right on the end of my pri. ( 12th turn ) another 1/2 - or so could help, 
maybe......

>From: "Tesla list" <tesla@xxxxxxxxxx>
>To: tesla@xxxxxxxxxx
>Subject: Re: Copper Banding?
>Date: Mon, 28 Feb 2005 19:56:04 -0700
>
>Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>
>
>Tesla list wrote:
>>Original poster: Kurt Schraner <k.schraner@xxxxxxxxxxx>
>>Hi David, Scott D,
>>well, the effect is _real_, and not a matter of words only. Let me
>>remind a former posting, where a comparison of measured vs.
>>calculated L values has been shown, at:
>>http://www.pupman.com/listarchives/2004/October/msg00018.html
>>I didn't yet get an answer, explaining in easy to understand
>>physical reasoning, about the difference. Might be, it can be
>>interpreted, by way of a higher interturn capacitance in ribbon
>>primaries, than "wire" spirals of the same planar geometry,
>>counteracting the inductance?
>>Regards,
>>           Kurt Schraner
>>Tesla list schrieb:
>>
>>>Original poster: "david baehr" <dfb25@xxxxxxxxxxx>
>>>
>>>In a previouse post, it was stated that a banded pri. would have
>>>less inductance than a copper tubing pri. Could someone explain
>>>this ? IF YA got 50' of copper tubing , and 50' of banded pri. ,
>>>wouldnt be about the same ????????////
>
>The reason is that a flat spiral made with tape acts as a stack of
>coupled filamental coils. If the coupling were unitary, the
>inductance
>would be the same of a single filament. But as the coupling between
>distant filaments is smaller than one, the inductance decreases.
>Consider for example two parallel filamental coils with inductance
>L.
>If they are at small distance, they act as a single coil with
>inductance
>L. If they are far apart, the coupling between them is
>insignificant,
>and the total inductance falls to L/2.
>
>Antonio Carlos M. de Queiroz
>
>
>