Re: Filter problem

Am 15.06.25 um 22:15 schrieb Phil Hobbs:

Gerhard Hoffmann <dk4xp@arcor.de> wrote:

Am 13.06.25 um 22:54 schrieb john larkin:
>

There is an inductor in the anode circuit, which resonates with the
valve capacitance (and a trimmer) at the output frequency.

>

There's no Miller effect only if the grids are zero impedance to
ground at 150 MHz.

>
There is no Miller effect when there is no voltage gain between
grid and anode that could be fed back via Cga. A shorted grid
just shorts the feedback. There is also no feedback when input
and output frequencies are really different or if the voltage
gain of the input device is kapputted by a cascode stage.

A unity gain common cathode stage has a Miller gain of 2, because it’s
inverting.

But first you have to achieve unity gain from fin on the input side
to fin on the output side, which is both unwanted/not needed and hard
to do in a mixer stage with a resonant circuit for the mixing product.
BTW  another good filter book:
Randall W. Rhea    HF Filter Design And Computer Simulation
isbn  0-07-052055-0
R.W.R. is the author of Eagleware Genesys which Agilent found
necessary to buy in spite of their own Advanced Design System.
His oscillator book is also good.

Cheers  Gerhard