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Re: Question on calculating resonance



Original poster: "D.C. Cox" <resonance@xxxxxxxxxx>

Many of these operate without the sec centerpoint grounded, ie, a 1/2 wavelength coil.

It probably best to ground the center point, spread the coils center point by 2.5 inches to 3 inches, and then operate as two separate 1/4 wavelength coils. The point is spreading the centerpoint is to set up the proper coef. of coupling so the coils are not overcoupled --- perhaps the single largest error most coil builders make (right next to poor quenching).

A single primary, usually copper ribbon drives both coils to opposite polarity simultaneously.

The toughest part of this design is end supports --- RF likes to track down almost anything. Glass rod works and G-10 phenolic rod work --- both expensive.

Correct winding length on each sec coil should be approx 5-6 x dia. of sec coilform.

Dr. Resonance




Original poster: "Angelini, Frank J" <FrankJAngelini@xxxxxxxxx>


I saw this diagram in an old magazine describing a horizontally oriented tesla coil. The secondary was approx 6-inches in dia and about 24-inches long. The primary was 8-inches in dia and maybe 10 turns of edge-wound copper strip. The primary was mounted in the center of the secondary and both were horizontally oriented. The primary was center-tapped and connected to a straight gap as shown. Not sure of the sec. winding length or cap values. T1 was 9 kV @ 500 VA.

Question: how would you calculate cap values for resonance? I thought, perhaps, that this is in effect, two 1/4-wave primaries and a 1/2-wave secondary.