Smiths Kelvin Hughes Nucleus 3 5000 Series, System Handbook

Page: 345 / 510

LOG RE CEIVER (CTX-A297)
21 A block diagram of the Log Receiver Assembly is
shown in
Figure 8c , below.
22
The Receiver comprises a logarithmic IF amplifier,
Automatic Frequency Control (AFC) circuitry and
tuning indicator circuitry.
23
Received radar returns are mixed in the RF head with
the local oscillator output to provide a 60 MHz
Intermediate Frequency (IF) which is applied to the receiver
input SKC.
AN TENNA TURNING MECH A NISM
24
Two versions are provided
(1) 25rpm
(2) 40rpm
25
The 25 rpm and 40 rpm versions are fitted with different
motors.
26
The basic unit contains the Antenna Motor, Gearbox,
RF Rotating Joint and Mount for the Antenna.
27
A slotted disc on the final drive provides 180 azimuth
pulses and a heading line pulse per revolution of the
antenna.
28
The HL PCB (CAE-A180) is mounted so that the
slotted disc rotates within the opto-coupler slots on the
PCB.
29
The PCB is fitted to an adjustable mounting bracket
assembly. Loosening the mounting pillars allows the
assembly to be moved positive or negative six degrees for
fine heading line adjustment. The slotted disc can be rotated
if the fine adjustment is not enough.
30
For Upmast Transceivers, the casing also contains the
RF head and electronic units. The coaxial cable
access hole is fitted with a bung.
SAFETY SWITCH
31
An ON/OFF switch located by the cable entries on the
outside of the case provides safety isolation of the
antenna motor when the switch is set to the OFF position.
Power is provided from the motor, thus also disabling the
transmitter when the switch is set to OFF
May 01 7c.8 Original
KH 2020
Chap 7c
I/P AMP &
BANDPASS
FILTER TR34
IC5
DISCRIMINATOR
5 STAGE
LOG AMP
IC6
SAMPLE
& HOLD
3 STAGE
LOG AMP
IC3 SUM
SELECTABLE
BANDPASS
FILTER
IC3 AMP
IC4
TUNE AMP
DETECTOR
TR33/TR37
LOWPASS
FILTER
IC2
VIDEO AMP
VIDEO
+14V
+14V
-14V
-14V
0V
BAND SELECT
LNFE TUNE
TUNE INDICATOR
I/F
I/F SCR.
TUNE
MOD SYNC.
VID.SCR.
3 x VIDEO
OUTPUT
CD-2184
Figure 8c - Log Receiver Assembly CTX-A297: Block Diagram