TM 11-5840-281-35/1
bias through the resistors in its emitter circuit.
change is present on the wiper of EL ATTEN control
Transistor Q4016 is added in series with transistor
R4064. The total change in voltage is across resistor
Q4015 to reduce the voltage from collector to base, and
R4065. Emitter-follower transistors Q4013 and Q4014 in
thus prevent breakdown of transistor Q4015. The base
tandem couple this volt- age from control R4064 to the
voltage of transistor Q4016 is returned to the voltage
base of transistor Q4015. Emitter-followers Q4013 and
divider between resistors R127 and R128. With resistor
Q4014 pre- vent the base current of transistor Q4015
R121 also in the divider, the base voltage of Q4016 is
from loading control R4064. Any change in supply volt-
approximately midway between the emitter of transistor
age is seen on the base of transistor Q4015 and
Q4015 and the collector of transistor Q4016, and the
transmitter will follow this voltage change. The volt- age
voltage is distributed equally across transistors Q4015
drop across resistors R4073 and R120 remains the
and Q4016. Emitter-follower transistors Q4013 and
same and the current remains the same.
Q4014 control the voltage on the base of transistor
Any change in supply voltage is seen in the base- to-
Q4015 and the current through resistor R120. The
collector voltage of transistors Q4015 and Q4016, and
attenuator currents are adjusted by controls R4063 and
the current through the attenuator remains the same.
R4064 around Zener diode CR4017. Zener diodes
Relay K4016 switches current regulation control to
CR4016 and CR4017, along with resistor R4065, are in a
control R4064, and supplies control current to the
voltage divider network from the positive supply voltage
elevation attenuator when azimuth Antenna
to ac common. The nominal breakdown (Zener) voltage
AS1292/TPN-8 is scanning.
is 18 volts for diode CR4016, and 15 volts for diode
When elevation Antenna AS-1291/TPN-8 is scanning,
CR4017; thus, the control voltage may be adjusted by AZ
relay K4016 switches current regulation control to control
ATTEN control R4063 or EL ATTEN control R4064 from
R4063 and supplies control cur- rent to the azimuth
18 to 33 volts below the power supply level. Assume that
attenuator.
control R4064 is adjusted to 25 volts less than the supply
voltage; when the supply voltage changes (this includes
1292/TPN-8 and elevation Antenna AS-1291/'TPN-
the 1200-Hz ripple), essentially the same
varies along the feedhorn
Figure 2-11. Ferrite attenuator switching and current regulator circuit, simplified schematic.
2-12
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