[Amps] grid resonance

[Tom W8JI]

Say what? I thought GDOs only detected parallel resonances. 
I was
taught that to check a series resonance one had to connect 
the two
open ends together, thus making a parallel resonance.>>

Think a little bit about the circuit and where the GDO is 
at. You aren't even measuring the grid at the socket pins. 
You are measuring the socket pins.

It's like measuring your feedline in the shack with a GDO to 
tell where the antenna connected at the other end is high 
impedance or low impedance! Why would anyone do that?

73 Tom