
4
-
2
B+ Routing for
VHF/UHF
Transceiver Boards
Refer to Figure 1 and your specific schematic diagram.
Raw B+ (7.5V) from the battery (Batt B+) enters the radio on the
transceiver board through a 3-contact spring pin arrangement (J3) as
B+, where it is routed through two ferrite beads on the VHF (E1, E101)
and three ferrite beads on the UHF (E1, E101, E106) to the RF power
amplifier module (U105) and ALC IC (U101, pin 13). Battery B+ is
fused, and then routed through the connector J1, pins 19 and 20 to the
VOCON board (J401, pins 19 and 20). The B+ supply is routed through
the VOCON board to the on/off/volume control knob (S901/R901) on
the control top/PTT flex at jack J901, pin 1. With the mechanical on/
off switch (S901) placed in the “on” position, switched B+ (B+ SENSE)
is routed from the control top flex at connector plug P901, pin 10 and
applied to the VOCON board at connector jack J901, pin 10. This
signal is also fed to a resistive divider R222, R223 on the VOCON board
so that the microcontrol unit (U204) can monitor the battery voltage.
The switched B+ voltage supplies power to circuits on the transceiver
board. The 5-volt regulator (U202), is applied this voltage through
decoupling component C125 to produce a stable 5.0 volt output. Raw
B+ (7.5V), which is connected to the ALC IC (U101), is switched
through the output (CATH1) to another 5-volt regulator (U106).
Regulator U202 supplies those circuits which need to remain on at all
times, such as the reference oscillator (U203), fractional-N-synthesizer
(U204), D/A IC (U102), and the ABACUS IC (U401). The D/A IC
controls dc switching of the transceiver board. The SC1 signal at U102
pin 12 controls transistors Q107, Q111, and the transmit 5 volts (T5).
Figure 1 . B+ Routing for VHF/UHF Transceiver Boards
Battery
7.5V
+
RF PA Module
U105
5V Regulator
U202
VCOB IC
U201
ALC U101
T5
L105
CR108
RX
L122
L121
Vcc
RF Amp
U1
Mixer
U2
Q107
R5
5V Regulator
U106
SB+
VHF/UHF Transceiver Board
MAEPF-24700-O
CR109
5V
S
Out
Fuse
To/From VOCON Board
SW B+
UNSW B+
Raw B+
T5
RX/TX
Ref Osc
U203
ABACUS
U401
D/A IC
U102
Synth
U204
IF Amp
Q601
Summary of Contents for ASTRO Digital Saber
Page 1: ... Digital SABER and R Portable Radios Detailed Service Manual ...
Page 19: ...1 14 Notes ...
Page 31: ...4 6 Notes ...
Page 37: ...5 6 Notes ...
Page 43: ...6 6 Notes ...
Page 81: ...12 4 Notes ...
Page 82: ... 6881076C10 68P81076C10 A Motorola 8000 West Sunrise Boulevard Fort Lauderdale Florida 33322 ...
Page 109: ...13 1 Block Diagrams Schematics Electrical Parts Lists and Circuit Board Details 13 ...
Page 111: ...13 3 NLD8892R VHF Transceiver Board Schematic Diagram 63B81094C71 O ...
Page 120: ...13 12 NUF6411K 800 MHz Transceiver Board Schematic Diagram 63B81094C75 O ...