Bill,
I have no intention of waging a war of words. Argue as you wish but
let's build a circuit and analyze it.
I just did a simulation in LTSpice of a tube (voltage controlled current
source) in parallel with a 2000 ohm resistance which has an open circuit
voltage of 2828V RMS. Then I loaded this down with another 2000 ohm
resistor (for a matched output network) which yielded 1414 V RMS or
1000W through this resistor. Then I placed a 100uH inductor (Q>1000) to
ground simulating the plate choke and at 9MHz calculated a current
through the inductor of 247mA RMS. I assume all is well so far. Next I
placed a 3.1pF capacitor (Q>1000) in parallel with the inductor which
resulted in parallel resonance at 9MHz. Now the calculated currents
were 247mA RMS through the inductor and 247mA RMS through the
capacitor. No change in current at all through the inductor. Changing
the circuit to be a series resonant one shows large current in the
inductor as expected. If someone can show me a fault in my circuit that
materially affects the results I will resimulate it. I can send anyone
the LTSpice file if they want.
73,
Larry, W0QE
Bill, W6WRT wrote:
> ORIGINAL MESSAGE:
>
> On Tue, 13 Oct 2009 19:37:27 0600, Larry Benko <xxw0qe@comcast.net> wrote:
>
>
>> At a slightly
>> higher frequency the parallel resonance has a combined extremely high
>> impedance and very small circulating current.
>>
>
> REPLY:
>
> Not so. At the exact frequency of resonance, the circulating current reaches
> its
> peak.
>
> One example of this is the working of a grid dip meter. At resonance, the
> circuit under test has the highest circulating current within itself and
> absorbs
> the most power from the dip meter, thus causing the dip.
>
> 73, Bill W6WRT
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