Other Circuits - Icom IC-FR5000 Service Manual

5-3 FREQUENCY SYNTHESIZER CIRCUITS
RX PLL CIRCUIT
The RX PLL IC (IC4) outputs resulting signal; phase-comparison
of reference signal (15.3 MHz) from the TCXO (X2) and fedback
OSC signal from the RX VCO. The phase-difference signal is
passed through the active loop fi lter (Q11, 14) and applied to the
RX VCO as the lock voltage. The voltage of RX LV (lock voltage)
is adjusted to appropriate one by "RX LVA" signal.
A portion of reference frequency signal (15.3 MHz) from the
TCXO (X2) is passed through the tripler (Q2) to extract 3rd
harmonic, then applied to the IF IC (IC5).
RX VCO
There are 2 VCOs; VCO for lower band (Q21, D8, 16, L17) and
higher band (Q20, D7, 15, L20), and these VCOs (=OSC freq.)
are switched by the VCO SW (Q26, 30). The OSC frequencies
of these VCOs are adjusted (=Locked) to desired one by the
RX LV signal (Lock Voltage). The output signals of these VCOs
are applied to the 1st mixer (L27, 32, D62) via buffer (Q25).
A portion of output signal from the buffer (Q25) is applied to
the doubler (Q32) to extract 2nd harmonic, then applied to
the PLL IC (IC4) via the LPF.
TX PLL CIRCUIT
TX PLL IC (IC3) outputs resulting signal; phase-comparison
of reference signal (15.3 MHz) from the TCXO (X1) and
fedback OSC signal from the TX VCO. The phase-difference
signal from the PLL IC (IC3) is passed through the active
loop fi lter (Q10, 13) and applied to the TX VCO as the lock
voltage. The rock voltage "TX LV" is adjusted to appropriate
one by the LVA signal. The OSC signal of TCXO (X1) is FM-
modulated by applied modulation signals.
TX VCO CIRCUITS
There are 2 VCOs; VCO for lower band (Q23, D10, 14, L62)
and higher band (Q22, D9, 13, L14), and these VCOs (=OSC
frequencies) are switched by the VCO SW (Q27, 28). The
OSC frequencies of these VCO are adjusted (=Locked) to
desired one by the TX LV signal (Lock Voltage).
The modulation signals applied to the Variable Capacitor
(VD; D18 or D30) vary the capacitor reactance of it for FM
modulation. The output signals of these VCOs are applied to
the YGR/PA circuits via buffers (Q24, 35).
A portion of these output signal is passed through the
doubler (Q33) to extract 2nd harmonic, then applied to the
PLL IC (IC3) via the LPF.

5-4 OTHER CIRCUITS

POWER SUPPLY
The power supply is switched by Q57 (ON/OFF). 5V (REF5)
from the regulator (IC30) is passed through L58 to supply to
CPU. The 5V also supplies to other sections of the repeater
via Q41 as "+5V."
8V from the regulator (IC27) are supplies to various circuits,
and also supplies to TX circuits as "T8V" and RX circuits as
"8V."
5V from the regulator (IC39) supplies DSP as "DSP5" and
supplies logic circuits; CPU, DSP, etc. via regulators (IC13,
14, 15).
The regulator "F8V" (IC41) provides the supply for FRONT
UNIT.
COMPANDER
The compander in the DSP (IC12) compresses the
amplitude of Demodulated signals in TX, and expands in RX
to provide high quality, high S/N ratio recovered sounds.
LEDs
DS1 (BUSY), DS2(PWR) and DS3 (TX) indicate the
repeater's status: Power ON, T/RX and Cloning.
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