Re: Primary resonators with very low L/C ratio

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Malcolm Watts by way of Terry Fritz <teslalist-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hi Alfred,

On 11 Jul 2003, at 19:25, Tesla list wrote:

 > Original poster: "Alfred Erpel by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <alfred-at-erpel-dot-com>
 >
 > **********
 > "... It's obviously impossible to make a [primary] coil with less than one
 > turn,..."
 > **********
 >
 > On a related topic:
 >
 > How about (for example) 10 primary coils wound clockwise connected
 > contiguously with 9 primary coils wound back on top of the clockwise coils
 > in a counter-clockwise direction for a net primary coil of 1 turn?
 >
 > In a helical coil they could take up considerable space vertically, but the
 > net inductance (and coupling?) would appear to be uniformly dispersed over a
 > large physical area.  Is this something that has been tried or worthy of
 > trying?

An interesting idea, but probably a rather costly one. It sounds like
the nett result is a single turn primary made from a piece of sheet
metal.

      My first working coil had a single turn primary about 15" in
diameter. The coil was a typical disruptive one. To make matters more
interesting, the primary cap consisted of a couple of 0.25uF
paper/oil-filled transmitter PS smoothing caps connected in series.
They occupied about 1/4 of the total primary turn. The Q was
appalling.

Malcolm

 > The same idea could be modified to give you very fine control over the
 > inductance if you devise a way to stretch and shrink one of the helical
 > coils (a la slinky) over the other one. (i.e. a 10 turn clockwise helical
 > coil can have the same inductance as a 9 turn COUNTER-clockwise helical coil
 > which is connected in series on top of it, thereby cancelling out the
 > inductance to zero, but you could vary the inductance infinitely down to
 > zero by stretching and/or shrinking the outer coil.)
 >
 > Regards,
 >
 > Al Erpel
 >
 >
 >