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Page Title: If. Output Selector
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a. Meter Detector V2A. The if. signal
.amplifier (para 29), also consists of four
f r o m the if. output selector (para 31) is
t u n e d pentode amplifier stages in tandem
coupled to the plate of meter detector V2A
to provide a high degree of selectivity and
( p i n 6) through capacitor C7. Capacitor
a m p l i f i c a t i o n .  B + voltages for the tube
C7 charges through V2A when the positive
p l a t e s and screens are provided through
portion of the input signal is applied to the
d r o p p i n g resistor R25 only when MEGA-
meter detector. During the negative portion
CYCLES band switch S1 (rear section) is
of the input signal, C7 discharges through
rotated to band 2, 4, 5, or 6. In the other
R7 and causes the peak level of the input
p o s i t i o n s , the switch cuts off these volt-
signal to be developed across R7 (negative
ages, which leaves the entire 1,600-kc if.
in respect to ground).
a m p l i f i e r  inoperative.
b. Meter Detector V2B. A p p r o x i m a t e l y
two-thirds of the incoming if. signal am-
31. If. Output Selector
p l i t u d e is coupled to the plate of meter
d e t e c t o r V2B through capacitor C11. The
The if. output selector selects the output
signal voltage is reduced to two-thirds of
o f either the 1,600-kc or the 455-kc if.
its original amplitude because of the volt-
s e c t i o n and couples it direct to the de-
age divider action of connecting one paral-
t e c t o r and electrometer assembly. Con-
lel network (resistor R5 and 10-uuf capac-
n e c t o r plug P6 and mating jack J5 apply
i t o r C8) in series with a second parallel
t h e output of the 455-kc if. amplifier to
n e t w o r k (resistor R6 and 5-uuf capacitor
the selector; connector plug P5 and mating
C 9 ) . Since the output signal from meter
jack J4 apply the output of the 1,600-kc if.
d e t e c t o r V2B has the same amplitude as
a m p l i f i e r to the selector. This selector
that of its input signal, two-thirds of the
s u b a s s e m b l y consists of a relay-operated
original if. input signal (from the if. am-
s w i t c h and a decoupling network. Relay
p l i f i e r ) is present across detector load
K6 is energized from the +150-volt source
resistor R8 (negative with respect to
when the MEGACYCLES band switch S1 is
ground). In the heater circuit, C22 and C23
rotated to band 1 or 3. This action positions
bypass residual if. signals to ground.
the relay movable contact so that the output
c. Electrometers V3 and V4, Dynamic
o f the 455-kc if. amplifier has a path of
C o n d i t i o n s . The voltage developed across
continuity, through connector plug P7, to
V 2 A load resistor R7 is coupled through
the input (J1) of the detector and electro-
r e s i s t o r R12 to the grid of electrometer
meter assembly. Ressistor R61 and capac-
V3. Likewise, the signal developed across
i t o r C127 constitute the relay decoupling
V 2 B load resistor R8 is coupled through
network. Feedthrough capacitor C128 func-
r e s i s t o r R13 to the grid of electrometer
tions as an rf bypass.
(1) In the CW PEAK and PULSE PEAK
32. Meter Detector and Electrometer
positions of the function switch (on
Circuit, Detailed Analysis
t h e main unit), thermal relays Kl
and K2 are open. Each half of the
m e t e r detector dual diode has an
B e c a u s e it is difficult to obtain meter
indications that show the true peak values
time-constant circuit. For V2A,
of pulses (especially at low-repetition
the time constant is determined by
r a t e s ) , the detector and electrometer cir-
the values of coupling capacitor C7
cuit has been especially designed to detect
and  20,000-megohm  load  resistor
these voltages. This circuit presents a very
R 7 . For V2B, an identical value
high impedance to the incoming if. signal.
t i m e - c o n s t a n t circuit is obtained
T h e current drawn is so small that the
by C11 and R8. Capacitors C7 and
output peak (or average) voltage detected
C11 charge very fast and discharge
i s identical in magnitude with the input
very slowly, so that the peak values
peak (or average) signal. The circuit
action is as follows:
of the incoming signal are detected

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