Hi Roger,
> I have been reading the mail about neutralisation and in particular
> the FL-2100Z circuitry. Like Ian, I looked at the circuit and thought
> 'that's pretty poor as it will depend totally on the settings of the
The FL2100 circuit I looked at can't possibly work. First, there
would only be a 180 degree shift if the Q of the tank was infinity.
That will not happen.
The actual phase shift will depend on tank loaded Q, and tank
resonance. It will be all over the place, and never correct at any
setting. That circuit probably causes more harm than good, like
floating grids of grounded-grid triode amps though low value
capacitors does.
> tuned circuit'. I've been pondering some more, and it seems to me that
> any neutralisation circuit on any tuned amplifier will depend on the
> settings of the tuned circuit(s).
No, it does not. The normal connection is directly across the tube
through a broadband phase inversion. Since anode and cathode
impedance affect the pass-through capacitance exactly the same
as an equal value neutralization circuit, input and output tuning do
not affect the null at all.
73, Tom W8JI
w8ji@contesting.com
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