Transmitter - Vertex VXR-5000 User Manual

VXR-5000 RPP Programming Software Instruction
RX Unit VCO Q5502 (2SK302GR) oscil-
lates between 112.4 and 152.4 MHz according
to the programmed receiving frequency and
repeater version type. A sample of the VCO
output is amplified by Q40l5 (2SC3356) and
returned to the prescaler / swallow counter in
Q40l4. There the VCO signal is divided by 64
or 65, according to a control signal from the
data latch section of Q1009 on CNTL Unit 1,
before being applied to the programmable
divider section of the PLL chip.
The data latch section of Q4014 also re-
ceives serial dividing data from microproces-
sor Q1009 on CNTL Unit 1, which causes the
pre-divided VCO signal to be further divided
by 11,240 - 15,240 in the programmable. di-
vider section, depending upon the desIred
receive frequency, so as to produce a 10-kHz
or 12.5 kHz derivative of the current VCO
frequency. Meanwhile, the reference divider
section of Q4014 divides the 12.8 MHz crystal
reference by 1280 (or 1024) to produce the
10-kHz (or 12.5-kHz) loop reference.
The 10-kHz or 12.5 kHz signal from the
programmable divider (derived from the
VCO), and that derived from the crystal are
applied to the phase detector section of
Q4014, which produces a dual phase-de-
tected 9-VDC pulsed output with pulse dura-
tion depending on the phase difference
between the input signals. This pulse train is
then converted to DC, low-pass filtered, then
fed back to varactor diodes D5501, D5502,
05503 & D5504 in the RX VCO Unit.
Changes in the DC voltage applied .to the
varactor diodes affect the reactance
In
the
tank circuit VCO Q5507, changing the oscil-
lating frequency according to the phase dif-
ference between the signals derived from the
VCO and the crystal reference oscillator. The
VCO is thus phase-locked to the reference
frequency standard. The output of RX VCO
Q5507, after buffering by Q5501, is delivered
for amplification to Q4012 (2SC3356) &
Q4011 (2SC3357) before application to the
first mixer, as described previously.
2-2
Transmitter
Transmitter VCO Q5002 (2SK302GR) os-
cillates between 134 -174 MHz according to
the programmed TX frequency and repeater
version type. The theory of operation of the
remainder of the PLL circuitry is similar to
that of the RX VCO Unit, however, dividing
data from the microprocessor is such that the
VCO frequency is the actual transmit fre-
quency.
IDC-processed speech audio from CNTL
Unit 2 is pre-emphasized by C20l0, R2006
and Q2002-4(uPC4747) before application to
the TX VCO. To prevent over-deviation, the
audio is processed by IDC (instantaneous de-
viation control) circuitry on CNTL Unit 2 be-
fore delivery to the TX Unit. Speech audio is
delivered to diode D5006 (1T363) from Con-
trol Unit 2, frequency modulating the PLL
carrier up to
±
5 kHz from the unmodulated
carrier at the transmitting frequency.
DCS modulation from control Unit 2 is low
pass filtered by Q3002 (NJM2904M), then ap-
plied to both the VCO and to the PLL fre-
quency reference, via reference frequency
standard X3001(GFS-720). The modulated
signal from TX VCO unit is buffered by
Q5001 (2SC3356) and Q3011 (2SK1577),
then passes through buffer-amp Q3010
(2SC3356). The signal then passes through
RF diode switch D3003 (HSU277) and ampli-
fier Q3009 (2SC3356). The signal level is then
attenuated before delivery to the PA Unit.
The signal first passes through the low-pass
filter formed by inductor L6001 and capaCItor
C6003 and then buffer amp Q6001 (2SC2954)
before being applied to pre-driver amplifier
Q6002 (2SC2954).
The transmit signal is then finally ampli-
fied by PA module Q6003 (M67741 [[H] in C-
versions, M67741 [L]-in A&B Versions) up to
25 watts. Harmonic and spurious radiation in
the final output is suppressed by as-pole
low-pass filter formed by inductors L6008,
L6009 and L6010 and capacitors C6016,
C6017, C6018. C60l9 and C6020 on the PA
Unit before delivery to the TX antenna jack. If
a CTCSS tone is enabled for transmission, the
sub-audible tone from the unit is low-pass
filtered, then mixed with the IDC-processed
speech audio.