Re: Coil specs

["Malcolm Watts" <M.J.Watts-at-massey.ac.nz> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Scott,
          It's just a mdeium sized one that could use a lot 
more power. I'm posting the reply to the list as you requested.

On 4 Sep 00, at 19:29, Scott.L.Hanson-at-seagate-dot-com wrote:

> Hi Malcolm -
> 
> Spectacular coil; congratulations!!
> 
> Care to share additional data with the list?
> 
> Tank cap type & value?

0.1uF, MMC polypropylene-foil caps. 10.5kVDCW    Was orignally 
home-rolled dry-fired poly/extended foil cap. MMC is a bit 
better in the loss dept. 

> Power supply type, current & voltage ratings?

Leybold demo transformer core, rewound to my spec. Ns approx. 
13,000 turns, Np about 550 turns, tappable down at 480 turns 
for max output. Vp about 230VAC, 50Hz. The lower Np brings the 
core towards saturation but not as far as the original 
transformer. 

> Spark gap: "blown"? Low velocity fan, or high-pressure compressed air
> blast?

A medium velocity jet from a compressed air hose tip blown 
angularly towards the gap. Needs fine adjustment along with 
the gap setting for best results.

> Secondary:  form material, diameter, wire gage?

Thickwall PVC drainpipe - just under 10" O.D. Copper dia. = 
0.56mm, 100% spacewound, 980 turns.

> Primary: conductor type, # of turns?

4 turns 3/8" Cu tubing, 26" dia approx.

> Top load: spun aluminum toroid, or ?

Contact-glued and shaped styrofoam rescued from old computer 
packing, covered with cooking foil.
 
> 
> As to the photos:
> Film (my guess) or digital camera?

Your guess is correct.

> Approximate exposure time?

3s per shot.

> Film speed (or "effective film speed" with digicam)

100 ASA

     The coil was designed and built back in 1993 to test 
Medhurst. Also to upgrade old benchtop model whose paper/oil 
cap had died. Originally 3 turn primary and sphere (about 
12uH). Upgraded with larger top and larger effective ROC last 
year, 1 turn added to primary to retune. Lp went from 12uH to 
about 18uH and Fr dropped from 155kHz to about 130kHz. The 
most striking thing about this mod was the immediate 
improvement in primary "Q". Vast. Could be *much* better still.

Regards,
Malcolm