From: Greg Leyh
Date: Thu, 28 Feb 2002 08:36:59 -0800
Subject: Re: [TSSP] Ion Cloud Loading
One might suppose that any quantity that distorts the electric field around the coil must necessarily change its tuning. Ion clouds do exhibit some continuous electrical properties; the ion trails left by meteors make for useful radio reflectors. I've been away from serious technical study for the last couple of years, and I don't understand how a cloud of discreet ions can exhibit properties of sheet or solid conductors. If the ions can persist much longer than one RF cycle, and a cloud of them can exhibit continuous conductor properties, then it seems feasible that the 'ion cloud' could bend the tuning, if slightly. However, based on measurements of streamer currents into free air (not striking grounded objects) I suspect that it's the additional capacitance of the streamer channels themselves which are actually responsible for any measured tuning shifts. On Electrum it appeared that a sizable fraction (30 to 60%) of the current feeding the sphere went into the single ended streamer, indicating that the displacement currents emanating from the streamer are comparable to those from the top electrode. Given the *low* Q of a secondary with a healthy arc hanging off the electrode, it's unclear how much even a significant tuning shift would affect the coil's effectiveness as a gratuitous 'air incinerator'. At 11:39 AM 2/27/2002, Malcolm wrote: >Hello all, > For a long time now, many have suggested that an ion cloud >hanging around the secondary terminal necessitates detuning the >primary downward somewhat to compensate. I have long doubted this >mantra (without proof) but have devised a relatively simple test that >could be performed to establish where the truth lies. My doubt arises >as I think that any detuning of the secondary can be explained (I >think) by capacitance (and resistance) added visible streamer length >alone. > The test does not involve spark production (important). >Instead, one uses the usual setup of a signal generator and aerial >probe to monitor the secondary ringing alone, and then introduce an >ion cloud around the terminal using some other devices (like ozone >generators. UV generators etc. Any significant shift in secondary >frequency should be quite observable. > I think this is an appropriate forum to check this out and add >to the knowledge base. Is anyone equipped to easily do this test?
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.