[Amps] grid resonance

[Vic K2VCO]

Tom W8JI wrote:
> 
>> Tom W8JI wrote:
>>> A mobile whip loaded with a coil is a series resonant
>>> system.
>>>
>>> Are you saying a GDO will not dip on a mobile whip Bill?
>>
>> The bottom of the coil is connected to the chassis through the low
>> impedance of the feed system.  The vertical radiator has capacitance to
>> the chassis (of course it has inductance, too).  Sounds parallel to me!
> 
> So the loading coil is like a trap, and the coax sees an open circuit?

No.  The vertical part has a capacitve reactance and a resistance, part 
of which is radiation resistance.  The whole system has a lower Q than a 
lumped-constant parallel tuned circuit.  The impedance seen by the 
feeder is thus lower.

> The idea a GDO can sort "good resonances" that make low impedances from 
> "bad resonances" that make high impedances seems pretty strange to me. 
> Can you tell me how it does that, rather than just  finding some type 
> of  resonance at the point where it is inserted? 

I certainly never said anything like that.

> Is there a way to measure impedance and Q with it Vic?

No, although the sharpness of the dip gives a clue to the Q.
-- 
73,
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco