Vertex evx-534, Service Manual, Page: 9 / 25

EVX-534/-539 VHF Service Manual 9
Circuit Description
3. PLL Frequency Synthesizer
The frequency synthesizer consists of VCO, TCXO (X1501),
and the custom IC Q1522 (RODINIA).
The output frequency from TCXO is 19.2 MHz and the toler-
ance is ±1.5 ppm in the temperature range –22 °F to +140 °F
(–30 °C to +60 °C).
3-1. vCo (v
oltage
C
ontrolled
o
sCillator
)
While the radio is receiving, the RX oscillator Q1506
(2SC5006) generates a programmed frequency between
186.85 and 224.85 MHz as 1st local signal.
While the radio is transmitting, the TX oscillator Q1505
(2SC5006) generates a frequency between 136.00 and 174.00
MHz.
The output from oscillator is amplified by buffer amplifier
Q1510 (2SC5006) and then is divided, one is fed back to the
PLL Circuit in the custom IC Q1522 (RODINIA). The other
one is supplied to the 1st mixer Q1523 (3SK293) through the
buffer amplifier Q1524 (2SC5005) in case of the reception. In
the transmission, the output is modulated to the FM (or digi-
tal) in the custom IC Q1522 (RODINIA), and then supplied
to the transmitter section described previously.
3-2. vCv (v
araCtor
C
ontrol
v
oltage
) C
ontrol
The tuning voltage (VCV) of the VCO establishes the lock
range of VCO by controlling the cathode of varactor diode
(D1502 (1SV279), D1504 (1SV282), D1507 (1SV279),
D1508 (1SV282) for receiving, and D1501 (1SV279), D1503
(1SV282), D1505 (1SV279), D1506 (1SV282) for transmit-
ting) from the custom IC Q1522 (RODINIA).
3-3. pll
The main constitution product of the PLL is equipped all with
in the custom IC Q1522 (RODINIA), so that all processing
regarding the frequency control is performed in the custom IC
Q1522 (RODINIA).