[Amps] grid resonance

[Vic K2VCO]

Tom W8JI wrote:

> Are you intending to say it is connected by displacement 
> currents? If so, it is still a series resonant circuit!  The 
> path is the feedpoint up through the coil, through 
> displacement currents to the chassis, and back to the 
> feedpoint.
> 
> That's a series circuit.

Let's say I take a coil and connect a capacitor across it.  If I couple 
RF into the coil from my GDO, I think you'll agree that it's a parallel 
circuit.

Now if you open the circuit and insert, say, an antenna analyzer in the 
gap, you get something similar to the mobile whip, which is a series 
circuit when looked at from the point of view of the antenna analyzer.

But we were talking about dipping a mobile antenna with a GDO.  And in 
that case, the 'gap' is some low impedance from the feed system in 
series with the parallel circuit formed by the coil, the whip, and the 
capacitance from the whip to the chassis.  You are then coupling RF into 
the coil from the GDO just like my first example.

So I would say that the mobile antenna, in operation, is a series 
circuit.  But when you dip it with a GDO, the dip indicates a parallel 
resonance.

I am not sure that this dip is at the same frequency at which the 
antenna will indicate zero reactance on the antenna analyzer, though!
-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco