Realistic trc-448 Service Manual page 7

TX: AM USB
RX : USB
OSC
Q10
011
TRIPLER
BPF
IC-1
MIXER
Q5
VCO
C16, 07
BUFFER
OUTPUT
At Pin 8 of IC-2 a Transmit Inhibit signal is available. It provides a high output (supply voltage to IC-2)
when the synthesizer attains a lock condition, or a low (0 volt) when not in lock. When the output is either
high or low, no phase error pulses are outputted that require detection. This circuit is used to inhibit
transmitter operation if the programmed frequency cannot be properly acquired. The lock detector output
will go low if a frequency error exists for more than 0.5 milliseconds. This signal is applied to the base of
Q8, turning it on or off. Thus the Transmitter can not operate in an unlocked condition of the PLL.
The channel selector switch also has an inhibit function, when the selector switch is set in between two
channel positions, Q13 is turned on to kill Q6.
33.4875/3 MHz
34.765 -35.2075 MHz
128-
1.72 MHz
11.1.1.1.71=
2V
RX : AM OSC Q9 LPF LPF
33.485/3 MHz
0.5V E
4 0 8 A
4
Q12
INH BIT
AMP
Q8
5V
-
L
CI
10.24 MHz
-r
4
IC-2
PLL IC
1, 7
8
5
k 9-1
CHANNEL
INHIBIT
SWITCH
Q13
AM and USB
(Receive and Transmit)
7.8025 MHz
15.605 MHz
19.1625 -19.6025 MHz
OSC Q1
CARRIER
BPF
Q3 Fr Q4
MIXER VCO
4-1
-57775
eT
35.2075 MHz
Q6, Q7
BUFFER
OUTPUT
1.5V
BPF
2V
33.4875/3 MHz
TX : LSB
RX : LSB
OSC
Q10
Q11
TR IPLER
BPF
IC-1
MIXER
LPF
1.28
1.72 MHz
LPF
INH BIT
Q8
Q12
5V1
AMP
10.24 MHz =
- r
IC-2
PLL IC
9--1
1, 7
8
CHANNEL
INHIBIT
SWITCH
Q13
LSB
(Receive and Transmit)
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