Re: Bi-Polar coil design

["Area31 Research Facility" <rwstephens-at-xxxxxxxxxxxxxx> (by way of Terry Fritz <twftesla-at-xxxxxxxxxx>)]

Terry,
 
Each secondary resonator can be wound the same sense and be identical.  They
should be tuned with their respective topload to resonate at or a few percent
below the frequency that the total tank circuit will operate at.  Both primary
coils can also be wound in the identical sense.  Run the interconnecting buss
between the insides of each flat spiral primary.  This will place the 1/2
voltage point of the tank circuit closest to the grounded end of the HV
resonator rather than a highest voltage node.  So looking from one end of the
primary circuit you go in the outside of #1.  Out the inside of #1 over to
inside of #2, then finally out the outside of #2.  The outsides being flying
taps. This all helps from a component interchangeability standpoint and allows
a manufacturer to just stock one primary and one secondary for a twin system. 
Once built and running you should find that you can completely remove one of
the resonators and dial your variac to about 1/2 the power level of normal twin
operation and you should get the same or slightly better performance from the
single remaining resonator.  That test is graphic proof that having fully 1/2
of your primary inductance hanging in the breeze away from your active primary
coil doesn't waste any practical levels of RF power.  In other words off-axis
series inductors are just fine as an alternative to tap changing for primary
tuning purposes.
 
Robert W. Stephens
Director
AREA31 Research Facility
AREA31 Radio Observatory
Co-curator
Hangar31 Vintage TV Museum
<http://www.area31-dot-org>www.area31-dot-org
>
> ----- Original Message ----- 
> From: <mailto:tesla-at-pupman-dot-com>Tesla list 
> To: <mailto:tesla-at-pupman-dot-com>tesla-at-pupman-dot-com 
> Sent: Wednesday, November 01, 2000 21:16
> Subject: Bi-Polar coil design
>
> Original poster: "Oxandale, Terry"
> <<mailto:Toxandale-at-SPP-dot-org>Toxandale-at-SPP-dot-org> 
>
>
> I have decided to undertake the construction of a bi-polar set of coils
> (two separate 1/4 wave coils). I am hoping to tap the vast knowledge and
> expierence on this list to answer some questions. I have seen some specs
> on a couple of bi-polar set-ups, but never any info on the design. It
> seems obvious to me that the primary coils on this set-up are in series,
> thus the pimary resonant frequency will be determined by the two
> inductors and one cap all in series. My question is what is the
> secondary coil's relation to each other. Should I consider them as being
> 2 inductors in series (as if the circuit would be completed between the
> two toroids by the streamer), or should they be considered in parallel,
> or considered separately with little influence on each other. The reason
> I ask is that if I am going to try to determine what size (L) of
> secondaries I will be winding, shouldn't I consider what the resonant
> frequency will be, and if so, then the physical parameters of my
> secondaries must take into consideration which of these two frequency
> numbers I should use. If you guys have the time, please feel free to
> inject any other information that I may need accomplish this task at
> hand. By the way, this coil will be of moderate power and size. I am
> planing on using 6" forms for the secondaries and an input of 2 to 4kw.
> These are the only set parameters at this time
>
> Un-Terry
>
>