Re: 1.5 Wave Coil

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Original poster: Terry Fritz <teslalist@xxxxxxxxxxxxxxxxxxxxxxx>

My friend Larry and I  built a solenoid style 1.5 wave coil. We didn't
do any testing or measuring, as this coil is just a diversion from a
large coil project.

A 1.5 wave coil has 4 top end capacitors equally spaced. One might
expect that this coil would either breakout across all four capacitors
at once, or only across the inner pair of capacitors, as this is a
shortest path. Nope, it breaks out preferentially across the outer
capacitor pairs. It sometimes will breakout across only the inner pair
of capacitors when we first start it up. But this is unstable and it
quickly reverts to breaking out across only the outer pair. (tuned
coupled oscillator behavior!)

We have not been able to get breakouts across the entire coil
simultaneously. But it may be possible with some fidgeting.

If you want to make your own 1.5 wave coil you will need a fairly long
inductor lest you overcrowd the primary between the voltage nodes and
get flashover.

Determine the wire length of 2/3 of your solenoid, this is your tank
frequency.
Find the inductance for 1/6 of your solenoid, calculate the top end
capacitance required to match this inductance to the wavelength
frequency. Subtract from this capacitance value the Medhurst self
capacitance of 1/6 of the solenoid. Split this calculated capacitance
value in half and make four top end capacitors this size.

We used about a half meter of quarter inch pipe to get the top end
capacitors away from the coil and primary.

You have three current nodes to chose from for placing your primary,
take your pick.

From: Jared Dwarshuis and Larry Morris