[Milsurplus] BC-9: Earlier and Later Operating Instructions.

[David Stinson]

----- Original Message ----- 
From: "Kenneth G. Gordon" <kgordon2006 at frontier.com>

> BTW, David, what is the purpose of the 20 volt source and the 
> resistor, pot, and S-1?
The 20 volt battery provides grid bias to the oscillator.
The resistors and pot form a voltage divider so
the large pot can adjust from 0 to -7V grid bias,
which sets the tube conduction at the point of
oscillation.   They use the divider because it
made the number of different batteries needed
to supply the set two instead of three.
The Signal Corps of 1921 had to pinch pennies.

> Also, in Mike's schematic, where is the filter "F"?
The "F" filter is in two sections, one isolating
the Plate B+ from RF currents and the
other isolating the Grid Bias supply from RF.
They are the RF chokes and .001 bypass
caps you see in the grid and plate circuits.

73 Dave S.