Figure 23. First and second rf amplifiers (70-220 mc), schematic diagram.

Figure 23. First and second rf amplifiers (70-220 mc), schematic diagram.

resonated by tuning inductor L207D, which

Resistor R238 and capacitor C253 provide

is mechanically coupled to the inductuner

d e c o u p l i n g for the plate circuit. Resistor

s e c t i o n s which tune the first and second

R 2 3 6 is a parasitic suppressor. Filament

r f amplifiers to the incoming rf signal.

b y p a s s capacitor C261 and choke L226

T h e oscillator tuned circuit consists of

p r e v e n t rf currents from circulating in

t u n i n g inductor L207D, trimmer capac-

t h e heater circuit. The rf output is de-

veloped across the primary of transformer

itor C249, and coil L215. Coil L214 is a

plate choke that suppresses undesired

T204 and capacitor C254, which make up

f r e q u e n c i e s . Feedback from the plate (pin

a parallel-tuned circuit tuned to 10.7 mc.

1 ) to the grid (pin 9) is made through

All other frequencies present in the output

are suppressed. The secondary of T204 is

capacitor C248. Resistor R234 is the grid-

c o n n e c t e d through terminal Y3 of switch

leak resistor. Plate voltage, 105 volts

S 2 0 1 (rear), to the input of if. step at-

positive to ground, is applied through volt-

t e n u a t o r AT201.

a g e - d r o p p i n g resistor R235 from terminal

W3 of band selector S201A when this

b. Oscillator V206B. A plate tuned os-

switch is placed in the 70-220 mc position.

c i l l a t o r is used to generate the local fre-

T h e oscillator signal is coupled from the

quency which is 10.7 mc higher than the

plate (pin 1) to the grid of the mixer through

i n p u t signal frequency. The oscillator is

c a p a c i t o r C245.