TM 11 5895-1096-40
CR2 provides shunt regulation.
h. Word Counter (U6). This IC is a decoded divide-by
k. Probe Power Supply.
The probe power supply
ten counter, used to control the operation of the encoder and
provides dc power to a BNC connector mounted on the test
transmitter functions. During its "0" condition it will generate
set front panel. DC power for the connector is obtained from
an encode transmission.
Code generation is initiated by
the 14 VDC power supply through an inductor (L2), and a two
application of a positive pulse on the reset input U6-15. This
transistor (Q3 and Q4) current limiter that protects the 14 VDC
reset pulse returns the divide-by-ten counter to its "0" state.
supply if the probe supply is improperly loaded.
As the encoder generates the code words, the word start pulse
from U3B-12 is counted until the tenth count or the Q9 output
I. Probe and Amplifier Assembly. The external probe
goes to a logic "I". With the Q9 output connected in a
and amplifier assembly picks up the 19.25 MHz signal from the
feedback loop to the clock enable input U6-13, the counter will
AN/GRA-114 transmitter modulator.
stop and hold the Q9 output "HI".
(1) 19.25 MHz signal pickup is accomplished by a
i. Buffer (Q1, Q2). The common collector configuration
2 /2 turn coil on the end of a small probe. This signal is
of transistors Q1 and Q2 provides the low-source impedance
amplified by a two stage junction-field-effect-transistor (JFET)
drive signal for the code output and EOW sync pulse.
amplifier (fig. FO-2) and then transferred to the test set by a
short length of coaxial cable.
j. 14 VDC Power Supply. All circuits in the test set are
(2) Interconnection between the test set and the
powered by this full wave rectifier circuit. The supply consists
external probe and amplifier assembly is accomplished by the
of a transformer T1, with a center-tapped secondary, mounted
use of cable W1 of Maintenance Kit MK-1752/GRA114. This
on the panel assembly with the remainder of the components
cable supplies the DC power to the assembly and transfers the
located on the circuit board. These components include two
19.25 MHz to the test set where it is separated from the DC
diodes, CR3 and CR4, which provide full wave rectification.
and coupled to the test set 19.25 MHz OUT jack.
Capacitors C12, C13, C14, and resistor R20 form the filter
network while diode
2-6
