Here is a one valve radio that I restored to operation that was built in 1922.
http://makearadio.com/restoration/pa...estoration.php
I drew the schematic and put it up on the page.
The radio originally used a 00A valve which is a "soft detector" or gas filled
valve. I didn't have one of those so I used a #30 valve as a replacement.
I had to add a grid leak resistor so that the grid wouldn't block.
I later plugged in a 01A and lit it with a 4 volt battery. That worked very
well too.
There is nothing like having a MW radio that uses 4 controls to select the station!
This would be a good radio to build if you want the olde time feeling.
Best wishes,
Dave