[Amps] Parasitics & Filament Sag

[Ian White GM3SEK]

Peter Chadwick wrote:
>Rich said:
>> If an L-network was resonant on the operating frequency,  infinite
>current would flow through it because the reactive components are
>equal, opposite, in series, and not in parallel.<
>Only because of your non-rigorous definition of resonance. AC theory 
>tells us that the only definition of resonance that holds for all cases 
>is that the applied voltage and current are in phase. The 'XL=XC' 
>definition is a very loose approximation, and falls over badly when Q 
>is low. There are occasions where it doesn't matter, but for an 
>understanding of what is happening, it is necessary to appreciate the 
>inherent errors in the approximation. The difference can be very 
>important where feedback is applied, because a tuning error can lead to 
>instability.
>Ian says that in practice, it doesn't matter. Not to the  appliance 
>operator, I suppose.

That wasn't the point I was making at all!

An L, Pi, Pi-L, T or similar network can be analysed, explained and 
designed in complete detail without ever using the concept of 
"resonance", so for these particular purposes the definition genuinely 
does not matter.




-- 
73 from Ian GM3SEK