this version was designed to operate with # 30's, I have 201's
installed in the pictures. I did this because I don't have enough
30's in a globe shape and these look better in the pictures. The
early versions of this set used 201's, but you needed an extra "C"
battery for the audio bias. With the 30's, you don't need the
extra supply. 201's work in this circuit, but with distorted
audio. To add the bias supply, simply disconnect the ground from
the secondary of the audio transformer and connect about -4 volts from
there to ground.
This set performs very well with good sensitivity and better than
average selectivity. The Browning-Drake owes it's improved
selectivity to the special detector coil which has a loose coupled
Both coil and capacitor assemblies are the original as sold by
National. Back then, you could buy just the L/C set or a whole
kit to build your own set. I purchased these about ten years ago
from Gary Schneider at Play
schematic shows a
variable capacitor in series with the
antenna, I substituted a 15 pf. fixed capacitor on my set. I
couldn't see any improvements
by using the variable capacitor.