2nd lF: 455kHz
12dB SINAD less than -l6dBu (144.000MHz ~ 147.995MHz)
Audio Power Output:More than 2.5W 10% Distortion
Speaker Impedance:8 ohm
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CIRCUIT DESCRTPTION
1) Receiver System
1. Front End
The signal from the antenna is passed through a low-pass filter and input to
the voltage step up circuit consisting Of L14. The signal from L14 is led to
the gate of Q1. D19 is the diode limiter circuit against the excessive input
power of more than 20dBm. Q1 is the FETwhich has two gates. The
voltage of the gate 2 is set higher to get the high gain and sensitivity. The
signal from Q1 is led to the triple band pass filter (L4, L5, L6), and gets the
high image rejection ratio.
2. Mixer Circuit
The signal from the triple band pass filter is converted into the first lF signal
of 17.2MHz. The receiving signal is led to the gate 1 of Q2, and the first
local oscillator signal is led to the gate 2 of Q2. To get the high conversion
gain, the local oscillator signal voltage is set to about 1V. To reduce the
high adjacent channel interference, the band width of the FL2 is set to
20kHz. The signal from FL2 is amplified by Q8, and input to FM IF system
IC3 of TK10487.
3. lF Circuit
The TK10487 has the second local oscilltor circuit, mixer circuit, detector
circuit, squelch circuit, and so on. Pin1 and 2 are the terminals of the crystal
oscillator circuit. Pin2 (emitter) is connected to the ground via the resister
R3 to prevent the oscillator from decreasing the power at the low temperature. Pin4 of IC3 is connected to FL1 directly because the matching resistor
for ceramic filter is built-in. The quadrature circuit (pin10 of IC3) is connected to the ceramic resonator X2 for the temperature stability and good
quality. The signal from pin11 of IC3 is connected to the LPF. The detected
AF signal, which has flat frequency characteristics, is led to the control unit
and used as both squelch signal and tone squelch signal. De-emphasis
circuit consists of R31, R32, C26 and C27. The LPF amplifier consisting of
Q5 and Q6 is located far away from the VR in the control unit, so it outputs
the high voltage signal to prevent S/N from the deterioration. The squelch
switch circuit consists of Q4 and Q16, and switches on/off at the point where
there is no voltage to prevent from the switching noise. The S meter signal
from pin12 of IC3 is led to the CPU in the control unit after adjusting the level
at D20 and VR5. The S meter signal is thermal compensated by TH1 and
stabilized. The noise amplifier consists of pin13 and 14, the built-in OP
amplifier in IC3. The output signal of noise amplifier is amplified by Q14,
rectified by D5, and then led to the pin15 (hysteresis comparator input) of
IC3.
4. AF Circuit
IC4 is about 5W audio power amplifier IC. When the capacity of pin1 in C16
is increased more, the output incidental noise becomes smaller. The highpitched tone becomes smaller at the same time, This radio's capacity of
C16 is determined considering the high-pitched tone.
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2) Transmitter System
1. Modulation Circuit
3) PLL Circuit
The microphone amplifier IC1 (IDC, LPF) consists of two operational amplifiers. The signal from the microphone is led to pre-emphasis circuit consisting
of C36 and R47 and then to the limiter circuit. The limiter circuit uses the
saturation of the OP amplifier. The amplified signal is input to the low-pass
filter IC1A. The output signal from the microphone amplifier is passed
through variable resistors VR2 for modulatlon adjustment and input to the
VCO unit. Sub tone deviation is determined by R24, R25 and VR2. The
radio does not have the adjustment variable resistor for sub tone deviation.
2. TX Amp. Circuit
The signal from VCO is ampriied by TX, RX wide band LO amplifier Q19.
The signal from Ql9 is passed through the transmission/reception selector,
and amplified byQ20 and Q15. The PA unit is driven at 200mW driving
power.
3. PA Circuit
IC5 is 50W powered amplifier module. The output power is controlled by
the voltage ofV1. The RF signal amplified 50W in PA is passed through D3
and three-stage transmission/reception low-pass filter, and input to the
antenna connector.
4. ALC Circuit
The power detection circuit consisting of D17 and D18 rectifies the output
signal voltage. The detected DC voltage is led to the VR1 (power adjust
trimmer), and amplified by Q3, Q9 and Ql3. Output power is controlled by
voltage of V1 in lC5 and collector voltage of Ql5. When the temperature
goes up unusually, the power down circuit consisting of R101 and TH2
works to prevent the device from the destruction.
The VCO unit is designed for the PLL circuit, putting the VCO on one side,
and PLL circuit on the other side.
Q301 in the VCO is grounded using the gate oscmator, and its frequency
covers 134MHz to 174MHz without transmission/reception shift circuit.
lC301 is pulse swallow system based PLL IC with the built-in prescaler,
which synthesizes 150MHzlband signal.
The loop filter consisting of Q302 and Q303 is the active type.
9 O1750_ToneBurstOutput
10 O ClockBEEPBeepToneOutput
11IActive Low MUPChannel Up Input (Microphone Control)
12IActive Low MDNChannel Down Input (Microphone Control)
13INoUseEID
14 O Active Low SQLSquelch Control (L: Audio is off.)
15 O ActiveHigh MUTMicrophone Mute (H: Mic Amp is off.)
16IActive Low RElRotaryEncoder Input
17 O ClockTO3ToneOutput
18 O ClockTO2ToneOutput
19 O ClockTO1ToneOutput
20 O ClockTO0ToneOutput
21IActiveHigh XWREEPROM Write Status External Input
22IActive Low RE2RotaryEncoder Input
23 O Active Low BPOBand Plan Detection Input (Common)
24IActive Low TIDTone Unit Detection Input
25IActive Low BUBack Up Signal Detection input
26IGNDGround
27lActive Low RSTResetInput
28IXinCrystal Oscillator Terminal (3.58MHz)
29 OXoutCrystal Oscillator Terminal (3.58MHz)
30IGNDGround
31IActive Low TDOCTCSS Tone Detection Output
32 O Active Hig
33 O NoUse
34IActive Low DD4Band Plan 4 (V/U Selection)
35IActive Low DD3Band Plan 3 (445/435 Selection)
36IActive Low DD2Band Plan 2 (5k/12.5k Selection)
37IActive Low DD1Band Plan 1
38IActive Low DD0Band Plan 0
39 O ClockSCLClock Output for EEPROM
DTDFor Trunking
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Port No. I/O LogicPinName Description
h
h
40 I/O ClockSDAData Output for EEPROM
41 O ClockCLKClock Output
42 O ClockDATDataOutput
43 O ClockST1Strobe Output for PLL IC
44 O ClockST2Strobe Output for CTCSS IC
45IActive Low SFTShift Key Input
46IActive Hig
47 O Active Hig