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Re: [Amps] R. MEASURES PRAYERS ANSWERED

To: amps@contesting.com
Subject: Re: [Amps] R. MEASURES PRAYERS ANSWERED
From: Steve Thompson <g8gsq@eltac.co.uk>
Date: Sun, 04 Jun 2006 15:16:45 +0100
List-post: <mailto:amps@contesting.com>

Peter Chadwick wrote:
> Rich said:
> 
>>1.  Pi-networks are never operated at resonance, they are operated  
> 
> close to resonance.  Low-pass Pi-networks resonate a bit lower than  
> the operating freq and high-pass Pi-networks resonate above it.<
> If it isn't resonant i.e. volts and amps are in phase, then you won't get 
> maximum output and will likely get worse IMD. I am aware that the US Extra 
> Class licence exam defines resonance as XL = XC, but this is only an 
> approximation, and falls apart very badly when the working Q is low. If you 
> use the only definition of resonance which holds up under all conditions i.e. 
> the input impedance of the network is resistive (as far as the tube sees it - 
> strays will have some effect if you calculate and compare with reality, 
> especially on the higher bands), then the pi network is resonant. So is the L 
> network, but if you use XL = XC, then both cases suggest that the circuit 
> isn't resonant.
Being pedantic, any definition of resonance has to apply to any and all 
systems, not just a tuned circuit. Whatever applies to a spring, or air 
column etc., has to be translated into appropriate electrical terms.

Steve
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