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TRC-70
20
CIRCUIT DESCRIPTION
|
The outputs of 04 and QO5 in the final stages passes
through low-pass filters for each band to eliminate
higher harmonic components. The low-pass filter out-
puts passes through transmit relay K115 and is applied
to the antenna terminal. The ALC voltage is detected
by L121, and the antenna current is detected by L123.
For bandwidth
information,
the 3-bit information
items (FL1 through FL3) sent from the TX-RX unit are
converted to 7 bits by decoder IC101.
Q107 through
Q113 turn on and relays K101 through K114 are changed
over for bandwidth selection. The bandwidth informa-
tion can be checked by checking that test points LPF1
through LPF7 are high (5 V). The band select relay can
also be checked by checking that LPF1B through LPF7B
are 5 V. The table 6 outlines the bandwidth informa-
tion.
Transmission and reception can be checked when
test points TX and RX are 5 V.
FL1/FL2|/FL3;
LPF NO. | Frequency (MHz)
H | HH
1
1.6050~2,9999
L | H | H
2
3.0000~4.9999
H | L | H
3
5.0000~6.9999
L
jb
|H
4
7.0000~8.9999
H}|Hy]L
5
9.0000~13.9999
Lj}
HL
6
14,0000~17.9999
Hi
LIL
7
18.0000~27,9999
Table 6 Bandwidth information
ANT
Ql
Q2.3
Q4.5
2SC197!
28C3133
28C2879
(0,Y)
KIS
PRE
a
ORIVE
ORIVE
FINAL
LPF
ont
P
>
a
8
zs
96
-
La
wy,
PA
vee
BIAS
—
LPF7
=
4
a
8T
a
IC1O}
FSB
7
DECODE
—_—
FLi-3
Fig. 16 Transmitting circuit configuration
¢
ALC voltage detector and antenna current
detector circuits
The ALC voltage is detected by L121.
Forward
waves
are detected
by D102, converted
to an AC
voltage, then sent to the TX-RX unit. The voltage is ap-
proximately 10 V in the low- to high-band range with
respect to the 47 kQ load of R112.
Reflected waves
are detected by D101 and sent to the TX-RX unit. The
reflected waves are adjusted by TC101
so that the
VSR voltage is minimum (approximately 0.5 V) when a
4 MHz frequency is output at
110 W.
For antenna current detection, the voltage detected
by L123 is detected by D103 and fed to the TX-RX unit.
The voltage is approximately 6 V in the low- to high-
band range with respect to the 47 kQ load.
ANT
OANT
Fig. 17 ALC voltage and antenna current detection
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