HOW IT WORKS The pi-network coupler
is the tuned grid circuit of the 6AG5 tube. An untuned plate
circuit is used to prevent oscillation. The output is resistancecapacity-coupled
and fed directly to the receiver input terminals where it may
be peaked by the receiver input circuits, depending on design.
Choke RFC1 maintains a high impedance to ground in the
grid circuit of the amplifier, and provides a grid return circuit.
Capacitor C8 provides an r.f, grounding path from the negative
side of the power supply.
PARTS LIST
CI-360-μμfd. variable capacitor
C2-140-μμfd.
variable capacitor
C3-100-μμfd. disc ceramic capacitor
C4, C5, C8-0.001-μμfd. disc ceramic capacitor
C6-100-μμfd.
disc ceramic capacitor
C7a/C7b-50-30 μfd., 150-volt electrolytic
capacitor
L1-3" x 1" coil (B & W Miniductor #3015-48
turns, tapped as shown in schematic)
R1-280-ohm, 1/2-watt
resistor
R2-12,000-ohm, 1/2-watt resistor
R3-40,000-ohm,
1/2-watt resistor
R4-100-ohm, 1-watt resistor
R5-10-ohm,
1-watt resistor
R6-2700-ohm, 1-watt resistor
R7-390-obm
resistance line cord (JFD #2190)
RFC1-2.5-mh. r.f. choke
S1-2-p., 5-pos. shorting switch (Centralab #1404)
S2-S.p.s.t.
toggle switch
SR1-Silicon diode Type 1N1084 (Sarkes Tarzian
-see text)
V1-6AG5 tube
It combines the impedance-matching properties of the pi-network
coupler with a signal booster amplifier. The power supply is self-contained
but, if desired, an external supply can be used. No expensive components
are required and the layout is extremely simple.