[AMPS] Pi-Net math

[Tom Rauch]

> It's not an alleged approximation...its a real one !  I'm surprised you'd
> ask this question since this exact point has been hashed over several
> times here on the refelctor.  Its also detailed well in the spreadsheet I
> sent you.
> 
> Phil

Phil,

It's a bit like the quality diodes. It takes a lot to extract anything 
remotely like a rational response.

Let me cut it to the bottom line, and save you time.

Rich removes the load and the source impedances from the tank, 
and measures the resonant frequency by his own definition of 
resonance. When ever anyone makes up his own definitions, like 
"quality" (in his definition quality=random diodes from a Digi Key 
catalog) or "resonance" (my dip meter doesn't dip when the source 
and load impedances are removed) you won't get through to that 
person.

Most people define resonance as a system with finite bandwidth 
where voltage and current are exactly in-phase (or exactly 180 
degrees out-of-phase). Some make up their own definitions.

When you hear someone saying he "dips the plate and resonates 
the tank" is going by the definition that current and voltage are in-
phase. When you hear "someone" arguing the tank is not 
resonant, it is because he removes the loads from each end of the 
tank and looks for a dip with his dip meter or calculates resonance 
with loads removed from each end of the network.

Rather than try to gently bring him into agreement with the rest of 
the world, it is better to just consider his view special.




   

 
73, Tom W8JI
w8ji@contesting.com

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