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Re: [Amps] grid resonance

To: dezrat@copper.net, Tom W8JI <w8ji@w8ji.com>
Subject: Re: [Amps] grid resonance
From: Peter Chadwick <g3rzp@g3rzp.wanadoo.co.uk>
Reply-to: g3rzp@g3rzp.wanadoo.co.uk
Date: Sat, 5 Aug 2006 14:23:26 +0200 (CEST)
List-post: <mailto:amps@contesting.com>
Actually, the GDO won't measure a parallel resonant circuit!
Just consider what happens. We'll put a coil in parallel with a capacitor, and 
couple (magnetically) the GDO to the coil. The magnetic field from the GDO coil 
induces a current in each turn of the coil to which it is coupled. The current 
induced is in series with the coil, and so the circuit is really a series 
resonant circuit, not a parallel one. The same thing happens with link coupling 
to a parallel L and C.
For most practical purposes it doesn't matter, because when the Q is greater 
than about 5, the difference in resonant frequency between series and parallel 
is minimal and may be ignored, although with low Q at VLF it can have 
interesting effects.
Again, in reality. a component with inductance and distributed capacity can 
show resonance on a GDO, merely because the distributed components  resonate 
somewhere.
Awaiting the flames!
73
Peter G3RZP
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