Less than -12.0µdB (0.25uV) [135 ~ 173.995MHz]
Selectivity-6dB : 12kHz or more
-60dB : 26kHz or less
Audio output power280mW (typical with an 8Ω load)
2
200mW (8Ω 10% THD)
CIRCUIT DESCRIPTION
1) Receiver System
The receiver system is a double superheterodyne system with a 21.7MHz first IF and a 450kHz second IF.
1. Front End
The received signal at any frequency in the 130.00- to 173.995-MHz r ange is
passed through thelow-pass filter (L2, L3, L11, C13, C14, C15 and C60) and
tuning circuit (L16 and D15), and amplified by the RF amplifier (Q11). The
signal from Q11 is then passed through the tuning circuit (L17, L18, L19 and
varicaps D13, D14 and D16) and converted into 21.7MHz by the mix er (Q9).
The tuning circuit, which consists of L16, L17, varicaps D15 and D13, L18,
L19, varicaps D14 and D16, is controlled by the tracking v oltage f orm the CPU
so that it is optimized for the reception frequency. The local signal from the VCO
is passed through the buffer (Q13), and supplied to the source of the mixer
(Q9). The radio uses the lower side of the superheterodyne system.
2. IF Circuit
The mixer mixes the received signal with the local signal to obtain the sum of
and difference between them. The crystal filter (XF1, XF2) selects 21.7MHz
frequency from the results and eliminates the signals of the unwanted frequencies. The first IF amplifier (Q10) then amplifies the signal of the selected frequency.
3. Demodulator Circuit
4. Audio Circuit
After the signal is amplified by the first IF amplifier (Q10), it is input to pin 16 of
the demodulator IC (IC5). The second local signal of 21.25MHz (shared with
PLL IC reference oscillation), which is oscillated by the internal oscillation circuit in IC1 and crystal (X1), is input through pin 1 of IC5. Then, these two
signals are mixed by the internal mixer in IC5 and the result is converted into
the second IF signal with a frequency of 450kHz. The second IF signal is output
from pin 3 of IC5 to the ceramic filter (FL1), where the unwanted frequency
band of that signal is eliminated, and the resulting signal is sent back to the IC5
through pins 5.
The second IF signal input via pin 5 is demodulated by the internal limiter
amplifier and quadrature detection circuit in IC5, and output as an audio signal
through pin 10.
The audio signal from pin 10 of IC5 is compensated to the audio frequency
characteristics in the de-emphasis circuit (R104, R103, C122, C121) and amplified by the AF amplifier (Q26). The signal is then input to pin 2 of the electronic volume (IC4) f or v olume adjustment, and output from pin 1. The adjusted
signal is sent to the audio power amplifier (IC3) through pin 2 to drive the
speaker.
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5. Squelch Circuit
2) Transmitter System
1. Modulator Circuit
2. Power Amplifier Circuit
The signal except for the noise component in AF signal of IC5 is cut by the
active filter inside IC. The noise component is amplified and rectified, then converted to the DC voltage to output from pin13 of IC5. The v oltage is led to pin 2
of CPU and compared with the setting voltage. The squelch will open if the
input voltage is lower than the setting v oltage .
The audio signal is conv erted to an electric signal in either the internal or external microphone, and input to the microphone amplifier (IC7). IC7 consists of
two operational amplifiers; one amplifier (pins 5, 6, and 7) is composed of preemphasis and IDC circuits and the other (pins 1, 2, and 3) is composed of a
splatter filter. The maximum frequency deviation is obtained by VR202 and
input to the cathode of the varicap of the VCO, to change the electric capacity
in the oscillation circuit. This produces the frequency modulation.
The transmitted signal is oscillated by the VCO, amplified by the pre-drive
amplifier (Q4) and drive amplifier (Q3), and input to the final amplifier (Q2). The
signal is then amplified by the final amplifier (Q2) and led to the antenna s witch
(D1) and low-pass filter (L5, L4, L3, L2, C16, C15, C14 and C13), where unwanted high harmonic waves are reduced as needed, and the resulting signal
is supplied to the antenna.
3. APC Circuit
Part of the transmission power from the low-pass filter is detected by D6, converted to DC, and then amplified by a diff erential amplifier. The output voltage
controls the bias voltage from the source of Q2 and Q3 to maintain the transmission power constant.
3) PLL Synthesizer Circuit
1. PLL
The dividing ratio is obtained by sending data from the CPU (IC9) to pin 2 and
sending clock pulses to pin 3 of the PLL IC (IC1). The oscillated signal from the
VCO is amplified by the buffer (Q5) and input to pin 6 of IC1. Each programmable divider in IC1 divides the frequency of the input signal by N according to
the frequency data, to generate a comparison frequency of 5 or 6.25kHz.
2. Reference Frequency Circuit
The reference frequency appropriate for the channel steps is obtained by dividing the 21.25MHz reference oscillation (X1) by 4250 or 3400, according to the
data from the CPU (IC9). When the resulting frequency is 5kHz, channel steps
of 5, 10, 15, 20, 25, 30, and 50kHz are used. When it is 6.25kHz, the 12.5kHz
channel step is used.
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3. Phase Comparator Circuit
The PLL (IC1) uses the reference frequency, 5 or 6.25kHz. The phase comparator in the IC1 compares the phase of the frequency from the VCO with that
of the comparison frequency, 5 or 6.25kHz, which is obtained by the internal
divider in IC1.
4. PLL Loop Filter Circuit
If a phase difference is f ound in the phase comparison between the ref erence
frequency and VCO output frequency, the charge pump output (pin 8) of IC1
generates a pulse signal, which is converted to DC voltage by the PLL loop
filter and input to the varicap of the VCO unit for oscillation frequency control.
5. VCO Circuit
A Colpitts oscillation circuit driven by Q1 directly oscillates the desired frequency. The frequency control voltage determined in the CPU (IC9) and PLL
circuit is input to the varicaps (D32 and D34). This change the oscillation frequency, which is amplified by the VCO buffer (Q5) and output from the VCO
unit.
4) CPU and Peripheral Circuits
1. LCD Display Circuit
2. Display Lamp Circuit
3. Reset and Backup
4. S(Signal) Meter Circuit
5. DTMF Encoder
The CPU turns ON the LCD via segment and common terminals with 1/4 the
duty and 1/3 the bias, at the frame frequency is 112.5Hz.
When the LAMP key is pressed, “H” is output form pin 50 of CPU (IC9) to the
bases of Q12. Q12 then turn ON and the LEDs (D12 and D17) light.
When the power form the DC jack or e xternal battery increases from Circuits 0
V to 2.5 or more, “H” le v el reset signal is output f orm the reset IC (IC11) to pin
33 of the CPU (IC9), causing the CPU to reset. The reset signal, however,
waits at 100, and does not enter the CPU untilthe CPU clock (X2) has stabilized.
The DC potential of pin 8 of IC5 is input to pin 1 of the CPU (IC9), converted
from an analog to a digital signal, and displayed as the S-meter signal on the
LCD.
The CPU (IC9) is equipped with an internal DTMF encoder. The DTMF signal
is output from pin 10, through R102 and R158 (for le v el adjust-ment), and then
through the microphone amplifier (IC7), and is sent to the varicap of the VCO
for modulation. At the same time, the monitor-ing tone passes through the AF
circuit and is output form the speaker.6. CTCSS Encoder The CPU (IC9) is
equipped with an internal tone encoder. The tone signal (67.0 to 250.3 Hz) is
output form pin 9 of the CPU to the varicap (D3) of the VCO for modulation.
5
6. Tone Encoder
7. DCS Encoder
8. CTCSS, DCS Decoder
9. Clock Shift
The CPU (IC9) is equipped with an internal tone encoder.The tone signal (67.0
to 250.3Hz) is output from pin 9 of the CPU to the varicap (D3) of the VCO f or
modulation.
The CPU (IC9) is equipped with an internal DCS code encoder. The code (023
to 754) is output from pin 9 of the CPU to the varicap (D3) of the PLL reference
oscillator . When DCS is ON, DCS MUTE circuit (Q15-ON, Q18-ON, Q16-OFF)
works. The modulation activates in X1 side only.
The voice band of the AF output signal from pin 10 of IC5 is cut b y sharp active
filter IC8 (VCVS) and amplified, then led to pin 4 of CPU. The input signal is
compared with the programmed tone frequency code in the CPU. The squelch
will open when they match.
In the unlikely e vent that CPU clock noise is present on a particular operating
frequency programmed into the radio , y ou can shift the CPU clock frequency to
avoid the CPU cloc k-noise. The output signal from pin 31 of the CPU turns on
Q30. Then the oscillation frequency of X2 will be shifted about 300 ppm.
5) M3826M8L
***
CPU
Terminal Connection
(TOP VIEW)
GP (XA0644)
6
No.Pin Name Function I/O PULogicDescription
1P67/AN7SMTI-A/DS-meter input
2P66/AN6SQLI-A/DNoise level input for squelch
3P65/AN5BATI-A/DLow battery detection input
4P64/AN4TINI-A/DCTCSS tone input/DSC code input
5 P63/SCLK22/AN3BP1I-A/DBand plan 1
6 P62/SCLK21/AN2BP2I-A/DBand plan 2
7P61/SOUT2/AN1 DCSWO-Activ highDCS signal mute
8P60/SIN2/AN0F/M/KEYI-A/DFunction/Moniter key input
9P57/ADT/DA2CTOUTO-D/ACTCSS
t one output/
DCS
to ne o utput/Tuning voltage out
10P56/DA1DTOUTO-D/ADTMF output/ EV R control output
11P55/CNTR1SCLO-PulseSerial clock for EEPROM
12P54/CNT R0TBSTI/OPulse/Act iv low T one burst output/UP input whi le tr unking
13P53/RTP1BP4I- - Band plan 4
14P52/RTP0MUTEI/O-Activ highMicrophone mute/Bank chang e input while trun king
15P51/PWM3CLKO-PulseSerial clock output for PLL,CTCSS,and trunking board
16P50/PWM0DATAI/O-Pulse
Serial data output for
PLL,CTCSS
, and tr unki ng boar d/ PLL unloc k si gnal i nput
17P47/SROY1STBTI/O-Activ low/Pulse
Trunki ng board det edt i on( when PSW is on) /Storobe signal t o trunki ng board
18P46/SCLK1STBPO-PulseStrobe for PLL IC
19P45/TX DUTXO-PulseUART dat a t r ansmission output
20P44/RXDRTXI-PulseUART data reception out put
21
P43/
/TOUT
BEEPI/O-Pulse/Activ low Beep tone/Band plan 3(when PSW is on)
22P42I/NT2RE2IAvtiv low
23P41/INT1RE1IAvtiv low
Rotary encoder input
24P40SDO-Avtiv lowSignal detection output
25P77PTTI-Activ highPTT input
26P76SDTIActiv highTrunking signal detection input
27P75P5CO-Activ lowPLL power ON/OFF out put
28P74T5CO-Activ lowTX power ON/OFF output
29P73R5CO-Activ lowRX power ON/OFF output
30P72AFPO-Activ lowAF AMP power ON/OFF output
31P71CLSFTO-Activ highCLOCK frequency shift
32P70/INTOBUI-Activ lowBackup signal detection input
33RESETRESETI-Activ lowReset input
34XcinXcin---35XcoutXcout---36XinXin---Main clock input
37XoutXout---Main clock output
38VssGND---CPU GND
39P27PSWI-Avtiv lowPower switch input
40P26SDAO-PulseSerial data for EEPROM
41P25C5CO-Activ highC5V power ON/OFF output
42P24LAMPO-Activ highLamp ON/OFF
43P23KI 0IAvtiv low
44P22KI 1IAvtiv low
45P21KI 2IAvtiv low
46P20KI 3IAvtiv low
51P13/SEG37H/LO--Tx power H/L
52P12/SEG36DA2O--DA converter for output power
53P11/SEG35DA1O--DA converter for output power
54P10/SEG34DA0O--DA converter for output power
55P07/SEG33SCRI-SCR input
7
No.Pin NameFunction I / O PULogicDescription
56P06/SEG32AFCO-Activ highAF tone control
57P05/SEG31S31O-58P04/SEG30S30O-59P03/SEG29S29O-60P02/SEG28S28O-61P01/SEG27S27O-62P00/SEG26S26O-63P37/SEG25S25O-64P36/SEG24S24O-65P35/SEG23S23O-66P34/SEG22S22O-67P33/SEG21S21O-68P32/SEG20S20O-69P31/SEG19S19O-70P30/SEG18S18O-71SEG17S17O-72SEG16S16O-73SEG15S15O--