Tuning Isis and Osiris

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Parpp807-at-aol-dot-com>

In a message dated 1/11/02 10:21:15 AM Central Standard Time, 
tesla-at-pupman-dot-com writes:

Hello Nick,

Thanks for the good info. Now you tell me.  :-))
I thought that splitting the 48 inch horizontal bipolar into a bipolar twin
would be mere tea and crumpets, basically just a spatial reconfiguration
with little or nothing changed electrically. Indeedy, the twin has already 
produced 
five feet of white hot spark with the tune points not very much changed from 
the original settings. I thot that
the voltages at the base of each resonator would still sum to zero since the 
bases
are connected with a piece of wire. But now there is arcing between the 
primary
and the grounded base and I don't know why.

If we can use John F's equation for spark length, your 96 inches shows 
a multitippyplier of 1.85. Can I expect a higher multiplier than 1.7 for a 
well tuned
coil? I figure Isis and Osiris should spark up at better than 80 inches.

I had again measured F sec for each secondary after spltting the bipolar. 
Each coil is exactly 1/2 L as the full coil. So nothing changed. Tuning with 
the
sig gen and an oscilloscope is nice but I also have a HP ACVTVM. I have an
antenna connected to each; you can't beat an analogue meter for tuning 
purposes.

Happy day,
Ralph Zekelman 
  

> Hi Ralph
>  
>  Tuning a twin coil is very similar to tuning an ordinary coil, but for one
>  key
>  difference, it takes about four times as long!  The problem is that every
>  adjustment to one primary must be matched by an adjustment to the other
>  to maintain overall system tune.  Something I have noticed on our 
relatively
>  small twin, Isis, and that Bill Wysock echoes in his Model 12 paper is that
>  the
>  two coils can be 'tuned' independantly to a certain degree by shifting
>  inductance
>  between the two primaries.  For example on a recent job we were running
>  with one of the coils in relatively close proximity to a black stretched
>  over
>  a metal frame, while the other was in clear space.  A substantial retuning
>  was
>  needed to 'balance' the two resonators, due to the proximity capacitance
>  effects of the metal frame.
>  
>  While at first sight this may seem odd  I suspect it is not in fact a 
tuning
>  process but a variation of the coupling of each resonator that allows some
>  compensation for imbalance, such as added capacitance.
>  
>  A twin is almost certainly more of a challenge both to design and operate
>  than a conventional monopolar coil, the reward is there, as our Isis system
>  shows - 8 feet from 2.7kVA.
>  
>  Safe Coiling
>  Nick
>