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Re: [Amps] grid resonance

To: Steve Thompson <g8gsq@eltac.co.uk>, amps@contesting.com
Subject: Re: [Amps] grid resonance
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Mon, 7 Aug 2006 09:55:07 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Steve said:
>In a finite universe I figure there's always going to be some 
capacitance and/or inductance and/or resistance between the 'open' ends 
of a series L and C, so everything is a parallel circuit. The issue is 
whether it's significant.<

All that does is complicate the circuit. The point I'm trying to get across is 
that the current induced in the coil produces an EMF in series with the coil. 
Not in parallel with it - if it was, a non resonant coil in a strong RF field 
would get hot. So the circuit is a series circuit of the EMF generator, the 
coil and the capacitor. Self capacitance of the coil gives it a modification to 
its apparent inductance and Q, and it becomes a more complex circuit.
One of those interesting theoretical matters that can occasionally be of 
importance, like transmitter conjugate matching arguments.
I must admit that I've never had a lot of use for GDO: the few I've used didn't 
help much and had all sorts of false dips, and I find that a tracking generator 
is a good way of finding resonances. For measuring L or C, very convenient is 
the Almost All Digital Electronics meter. Certainly for most ham work, that 
gets you into the 'near enough' region.
73
Peter G3RZP
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