1.3 Scanner unit
8
IF Amplifier board (03P9321)
The 60 MHz IF amplifier consists of Q1, Q2, U1 and U2, and provides the bandwidth of 7 MHz.
The tuning level detector, U3 to U8, detects the main bangs to indicate the tuning level.
Fig.1-6 Block Diagram of IF AMP Board (03P9321)
MIC (RU-9458B)
The circulator in the module switches between the transmitting and receiving microwave circuits
so that the transmitting radio energy is efficiently transmitted to the antenna without leaking to
the receiver side and the receiving radar signal from the antenna is sent with efficiency to the
receiver without leaking to the transmitter side.
The receiver circuit consists of a diode limiter, an RF amplifier, a balanced mixer and an FET
oscillator. The diode limiter protects the amplifier and balanced mixer from the excessive input
power. The mixer converts the input microwave signal to the 60 MHz IF signal. The oscillator is
voltage-controlled and outputs the signal to the mixer.
MD board (03P9270)
The MD board consists of a power supply circuit and a modulator.
There are two DC-DC converters in the power supply circuit: one generates –6 V, +5 V, and +12
V and the other magnetron heater voltage and TX HV. In the DC-DC converter, drivers Q803
and Q832 are driven by PWM controllers, U801 and U805 respectively.
The magnetron current, –6 V, +5 V, +12 V, +8 V (magnetron heater voltage), and TXHV can be
measured at the test point TP804.
The modulator in TX circuit receives the transmitting pulsewidth selection signals, PL-A and
PL-B, from INT board, and the trigger signal from the display unit. One-shot multivibrator U851
generates the transmitting trigger pulse of which the pulsewidth depends on range setting.
VR851 and VR852 adjust the output power of the magnetron. The pulse is boosted up by T851
and applied to the magnetron.
Q1
First
IF AMP
Video
signal
output
Third IF AMP
Video detector
U1
60 MHz IF
LC filter
U1
Second
IF AMP
GAIN CONT signal
(From INT Board)
TUNE IND OUT
TUNE GATE IN
Tuning level
detector
U3 to U8
60 MHz IF
LC filter
Video
amplifier
U2
9 V
VR2
To Next Page
Loading...
