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Re: 200kHz good, 100kHz better. (fwd)
Greeting all,
Sandy wrote
>What is the construction / geometry of your toroid ?
>I'm curious about the eddy currents ------
Nothing special - its a 1m lenght of 3" diameter pipe insulation,
wrapped round a cardboard disc and covered in aluminium
foil tape. 6" above the coil (12" diameter polythene bucket)
the foil got slightly warp, 12" up no aparent warming effect.
But also no obvious increase in power output, though the
resonance frequency rose slightly (Capacitance between
toroid and coil dropped).
The toriod acts as a shorted turn - I read of someone cutting
a slot in their toriod to reduce this but with no great affect.
Duane Byland did some experiments with counter poises.
Which also are prone to eddy currents.
A grounded Aluminium sheet improved performance but
the best results were with a radial arrangement of wires
(100's of them) coming from a single ground point.
I considered making a foil pattern on a PCB but then I
looked at the cost of PCB's :( .
- I'll try the insulation - need to send of for a couple
of bits of heat shrink tubing, and a new can of Acrylic)
have fun
Alan Sharp (UK)