5 CIRCUIT DESCRIPTION AND SCHEMATIC DIAGRAMS RT2048
5.4.9. RF POWER CONTROL
The power adjustment loop consists of Q04, Q03, Q05 and Q1.
Q04 is the power detector which together with Q03 forms a differential circuit.
The differential circuit controls Q05 and Q01 which are made as a Darlington transistor.
C22, R17, and R15 make a feed-back in order to slow down the loop.
Q12 controls the on/off function through the differential resistor R18.
Q06 is the power indicator transistor which gives the microcomputer information about power on the output from
the RF power amplifier.
This information is active about 0.3 Watt.
Q13 controls the 1 Watt/25 Watt change-over transistor Q07. If the power is lower than about 15 Watt in the 25 Watt
position the power indicator transistor Q06 will make a smooth change-over to 1 Watt position through resistor R61.
The 25 Watt adjustment is done on R21 and the 1 Watt adjustment is done on R19. The 25 Watt has to be adjusted
first because it has influence on the adjustment of 1 Watt.
5.4.10. 8V POWER SUPPLY
The regulator U01 is supplied from the internal 13V supply.
The adjustment of the voltage is done on resistor R04.
The 8V supply is divided into 2 more supplies in the antenna relay, the 8V TX supply and the 8 RX supply.
Important Note:
Due to a change of RF Power Module (U04) from the Mitsubishi S-AV6 to the Mitsubishi RA35H1516M, a hardware
redesign of the original RX/TX module 4 (625448) and Synthesizer module 625451 has been necessary.
The revised RX/TX module is identified as 60-127059 and comprises the introduction of a voltage divider consisting
of R69 and R70 reducing the RF power control voltage for the RA35H1516M RF Power module (U04) to max 5.5
VDC.
Pls. refer to schematic diagram 93-127059 rev. B (or later).
The RX/TX module 60-127059 can be used only with the Mitsubishi RA35H1516M RF Power Module and the
revised synthesizer module 60-127230
Page 5-13
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