>
>> >The series resonance actually makes the input impedance of the
>> >tank look like only a few ohms!
>> >
>> This is true only when the series resonance is not offset from the
>> parasitic freq. L-networks are never resonant. When the resonance is
>> Near but not dead-on the parasitic freq., the L-network effect comes into
>> play and the potential is substantially increased.
>
>You must be using a new definition of resonance. Can you tell me
>what you mean?
>
zzzzz
>This is a series-resonance, not L-network, and it is shunting the
>path the tube must drive on VHF.
>
L-networks transform Z. They shunt not.
>If the tank could freely pass harmonics, or step up the voltage at
>VHF to high levels, the amplifier would be a TVI nightmare.
>
If the tank were a high-pass Pi, VHF parasitic oscillation would be
unlikely.
>> >It actually makes it impossible for the tube to drive significant
>> >voltage at the tank at VHF!
>> >
>> Ä You seem to have missed the word "Near", Tom.
>
>The impedance of the capacitor is highest at dc, and is reduced as
>frequency is increased. That's why the tank is a low-pass network.
>
>If the parasitic is NEAR the fundamental frequency, or lower than
>the fundamental frequency, it could indeed arc the tank
>components over...maybe.
>
At the HF/MF fundamental freq. there is not enough feedback C to sustain
oscillation.
>Most people know the tank is a poor pass system for VHF energy,
>you might have a hard time confusing them.
>
>> Ä Which TV station is on 120MHz?
>
>Nice try. Now we have single frequency parasitics exactly on 120
>MHz, where the tuning capacitor has about ten ohms of reactance,
>driving the tank capacitor with thousands of volts.
>
Mr. Rauch conveniently disappears the series-resonance in the Tune C to
support his agenda.
>What happen to your claim about grid resonance at 80 MHz, did it
>move in this application to fit your needs?
no. The tubes can oscillate above grid resonance.
>
>
later, Tom.
- Rich..., 805.386.3734, www.vcnet.com/measures.
end
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