Pulsar TCF-10B, System Manual, Page: 169 / 249

15.1.1 CLI and Discriminator Control
Panel
(This panel is shown in Figure 1-1.)
Operator controls are as follows:
LEDs
• Noise (Red)
• Low-Level (Red)
Internal and External (Remote) CLI
Meters
(Optional.)
15.1.2 CLI and Discriminator PC
Board
(The CLI and Discriminator PC Board is shown in
Figure 15-1.)
Operator jumpers are as follows:
Jumpers
JU1 Extra Wideband (soldered jumper)
JU2 NO/NC Low-Signal contacts for relay
(K1)
Potentiometers
R1 Internal CLI Full-Scale Adjust
R40 Low Level Adjust
R104 External CLI Full-Scale Adjust
Factory-adjusted potentiometers
R18 Offset Adjust
R25 AGC Adjust
R37 CLI Zero Adjust
15.2 CLI & Discriminator Circuit
Description
The 20 kHz input signal (at connectors A/C-24)
passes through an L/C Bandpass Filter (L1, L2
and associated components), enroute to the
Current-Controlled Amplifier (I2). The upper half
of I2 is used as an AGC amplifier for the input
signal. The Buffer Amplifier (I1a) buffers I2. The
output of I1a (at TP1) connects the AGC’d input
signal of the Limiter (see sheet 2 of the schematic
in Figure 15-3). The output of I1a also proceeds
through the Full-Wave Rectifier (I1b, I1c), which
extracts the amplitude of the signal at I1a. The
Full-Wave Rectifier output is compared, at the
input of the AGC Integrator (I1d, R28, C10), to
the level determined by resistors R25 and R26; the
output is a dc level of ±10 V.
AGC voltage is applied to the Logarithmic
Current Source (I5a, Q1, lower half of I2). The
output of the Log Current Source is applied to I2,
pin 1 to complete the AGC loop. The voltage
divider (R119, R4, R3) converts the ±10 Vdc AGC
signal to a (0 to 10 Vdc) signal that drives the
Internal and External CLI circuits. The Internal
CLI Full Scale Adjust potentiometer (R1) is used
to adjust the Internal CLI Meter reading to +10
dB, with a 20 kHz input of 3.162 Vp-p.
The external CLI drive circuit consists of pulse
width modulator (I11), optical isolator (I-14), Q2
and associated components. The output of buffer
I5-B is fed to I11. The pulse-width modulator
control chip (I11) operates to cause proportional
voltages between: I11 pins 2 and 15 and I-14 pins
1 and 2. This is accomplished by integrating the
output pulses at I11 pin 10, and using the filtered
Vdc as a reference that is fed to I11 pins 1 and 16.
Given this condition, the Vdc at pins 1 and 16 will
always be the same as the Vdc at pins 2 and 15.
Since the output voltage at I11 pin 8 is 180° out-
of-phase with the Vdc at I11 pin 10, the average
Vdc through the input of I-14 will always be
Page 15–2 January 1996
TCF–10B System Manual
Technologies, Inc.