TM 11-6625-524-14-2
CIRCUIT FUNCTIONING
5-1. Block Diagram
e. The alternating current (ac) signal from the
o u t p u t stage is rectified by a synchronous
d e m o d u l a t o r (3A2Q7 and 3A2Q8) and the
derstood by reference to the block diagram (fig. 5-
resultant dc output is used to provide heavy
1).
o v e r a l l dc feedback and temperature com-
a. The input signal is sampled and detected by
pensation. The dc output is also linearized in the
the rf probe. The direct current (dc) output signal
output circuit and connected to the indicating
from the probe, after passing through the at-
meter.
tenuator section of the range selector switch, goes
f. The dc modulator output is also connected to
through an input filter which rejects power line
a driver (3A2Q1 and 3A2Q2) which drives a
frequency components which might cause a
reference amplifier (3A2Q3 and 3A2Q4).
measuring error.
b. A single-pole, double-throw dc modulator
g. The output from the reference amplifier is
(3G1) then converts the dc signal into a nearly
fed to the synchronous demodulator. The phase
symmetrical square wave.
relationship between the reference amplifier and
the input signal determines the polarity of the dc
amplified by a high impedance, narrow band
output which is connected to the indicating
preamplifier (3A2Q9 through Q12). Its narrow
meter.
bandwidth also improves the signal-to-noise
h. An electronically regulated power supply
--
ratio.
(3A1CR1 and 3A1CR2) plus transistors delivers
-14.5 volts to the amplifier. The amplifier
in the driver and output stage (3A2Q13 and
divides the power supply voltage to - 6 volts and
3A2Q14).
+8.5 volts.
