04-07-2020, 12:46 PM
You'd be better with a 470K to 2M resistor to ground at the diode input and 1M at the grid as grid leak and DC load. The DC conditions are undefined on the diode and grid. In practice there is likely a negative charge on g1a and g1b, so diode is conducting when AC voltage is above that voltage. Thus with the two resistors it will be more sensitive.
The only AM diode detectors that work well with no DC path on the input is the two diode peak detector, which needs a DC load. So you could add a 2nd 1N60 rather than an input resistor and only add the grid leak/diode load.
A trick I've done to make a simple transformer for RF or IF is two resistor style inductors side by side or random wind fine wire on one as a secondary.
The 1j42a was one of the last Rod Tubes and was difficult to make. For years no-one was selling them. The 1j24b is the next best if you don't need dual grid.
The only AM diode detectors that work well with no DC path on the input is the two diode peak detector, which needs a DC load. So you could add a 2nd 1N60 rather than an input resistor and only add the grid leak/diode load.
A trick I've done to make a simple transformer for RF or IF is two resistor style inductors side by side or random wind fine wire on one as a secondary.
The 1j42a was one of the last Rod Tubes and was difficult to make. For years no-one was selling them. The 1j24b is the next best if you don't need dual grid.
