04-07-2020, 04:36 PM
You can try replacing the 18M input resistor with an RF choke.
Or a second diode ( anode to ground, cathode to existing cap & anode) and then the only RF and AF load is the grid resistor. Once the input capacitor is charged the only AC or DC load is the grid resistor. Same is true with an RF choke.
The anode load of V1 can be a ferrite ring (or regular inductor at right angles to ferrite) and then a 2nd gang equal to tuning cap, if the inductor equals ferrite rod, will tune. It can be earthed, same shaft as the HT rail is decoupled and a dead short to RF and AF (I hope!).
The modified diode circuit, your own or any of my suggestions, will only load Q of the anode coil and 2nd tuning cap by the load resistance of the grid resistor, especially if the dual diode circuit is used. It's more complicated if a resistor, choke or transformer is used.
Or a second diode ( anode to ground, cathode to existing cap & anode) and then the only RF and AF load is the grid resistor. Once the input capacitor is charged the only AC or DC load is the grid resistor. Same is true with an RF choke.
The anode load of V1 can be a ferrite ring (or regular inductor at right angles to ferrite) and then a 2nd gang equal to tuning cap, if the inductor equals ferrite rod, will tune. It can be earthed, same shaft as the HT rail is decoupled and a dead short to RF and AF (I hope!).
The modified diode circuit, your own or any of my suggestions, will only load Q of the anode coil and 2nd tuning cap by the load resistance of the grid resistor, especially if the dual diode circuit is used. It's more complicated if a resistor, choke or transformer is used.
