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Key Scan
Key scan by MCU pin26 (BUS01) and pin27 (BUS02) control, apply difference step DC voltage
input to A/D pin26 and pin27. ----- MRF55/75
MRF75 only --- Digital volume rotary operation by encoder K300 control MCU pin14 (bus15)
and pin15 (bus16) realization. The DC power operation by encoder K300 push switch control
MCU pin9 (bus11) achieved.
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DC Power Controller
The unit DC power supplies is 13.8V and path as follows:
MRF55: T102 – L124 – SW100 (Rotary switch) – IC111 (LM7805) – VCC+5V output.
MRF75: T102 – L124 –-- R125 – IC108 (LM7805) -- +5V output to MCU (CPU-DC).
Q124 (KTA1276Y) -- IC111 (LM7805) – VCC+5V output.
55/75 RX: Vcc+5V – Q122 E – Q122 C – RX-Vcc+5V output.
55/75 TX: While the PTT key was press down, the TX-ON control pin of MCU is low, so, Q120
will working and the Q122 cut-off.
Vcc+5V – Q120 E – Q120 C – TX-DC-5V output.
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VCO & PLL
1. The VCO oscillator stage by Q112, L115, VD100 and some resistors and capacitors
component buildup. TX and RX VCO change by Q111 control.
2. The PLL IC used Toshiba brand TB31202FN and the local frequency is 20.95MHz.
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TX Pre-amplifier
TX pre-amplifier stage by RF transistors Q127, Q110 and coils L106, L114 and external some
resistors and capacitors buildup the 160MHz amplifier.
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TX Driver & Final Amplifier
TX driver and Final amplifier stage by Mitsubishi’s RF power module RA35H1516M buildup.
The pin1 is RF signal input, the pin2 is Gate control, the pin3 is DC power supplies input, the
pin4 is RF power output and the heat sink is ground.
