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Motorola Bpr40 Magone Detailled 6816102h01 A Manual

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    							Transmitter System and PLL Synthesizer2-3
    3.0 Transmitter System and PLL Synthesizer
    The transmitter consists of: Microphone, Pre-emphasis, Modulator, Drivers, Power Amplifier, Low-
    Pass Filter, Antenna Switch and an Auto-Power Control.
    3.1 TX Power Stage
    The TX VCO output signal is channeled by the TX power stage via an attenuator. The attenuator is 
    pie style resister attenuator, and is used for isolation between the VCO and power amplifiers. 
    The TX Power stage is consist of: pre-drive (Q401), drive amplifier (Q402) and final amplifier 
    (Q403). The -4dBm TX RF signal from the attenuator is increased to around +25dBm by the pre-
    drive and the drive amplifier.
    The TX signal from drive amplifier is next amplified by final amplifier (Q403). It passes through a 
    strip line for impedance matching, and a low pass filter to suppress unwanted harmonics via the 
    antenna switch.
    3.2 Antenna Switch
    The antenna switch is for enabling the TX section and the RX section to share the antenna. 
    In transmit mode, PIN diodes (CR401, CR301, CR302) are forward biased and these enable the RF 
    signal to pass to the antenna.
    3.3 Low Pass Filter
    The TX Low Pass Filter consist of a fifth Chebyshev filter and reduces the unwanted spurious for TX 
    output power from final Amplifier : C426~430, L409, L410.
    LPF
    ANT-SWFINAL
    AMP
    CURRENT
    DETECTDRIVE
    AMP
    APCP.DRIVE
    AMP
    VCO
    PLL
    PLL DATA
    VCTCXOREG. 5.8V
    U106
    U701 Q401 Q402 Q403
    R417 CR401
    BATT.LOOP
    FIL.
    U401
    AUDIO
    (From filter)
     3DB
    ATTEN 
    						
    							2-4Transmitter System and PLL Synthesizer
    3.4 Auto-Power Control
    The Auto-Power Control (APC) keeps the current constant to the final amplifier (Q403). The current 
    into Q403 of the final amplifier is sensed across resistor R417. 
    The voltage difference across R417 is amplified through U401 by the ratio of R423 to R417. The 
    differential signal at the output of U401 is passed to Q404 and Q405 which then produce a constant 
    power output to the antenna. If the current is changed due to a change of battery voltage or load, the 
    APC controls gate voltage of Q403 and the collector voltage of Q401,402 to keep the TX power 
    stable. 
    This circuit stabilizes TX power at a pre-determined level adjusted by R425 (High Power), R426 
    (Low Power).
    3.5PLL Synthesizer
    3.5.1 12.8 MHz VCTCXO
    Reference frequency is 12.8Mhz VCTCXO (Voltage Controlled Temperature Compensated Crystal 
    Oscillator). Main frequency can be adjusted by the chip trimmer of VCTCXO. This frequency 
    provides a reference to the PLL. It has a frequency stability of 
    ± 2.5PPM at -30º to +60º.
    3.5.2 PLL IC and Loop Filter .
    The input frequency of 12.8Mhz is channeled into PLL IC (U701) pin 8. It is divided to 6.25Khz or 
    5Khz by a reference counter, R. The RF signal input from the VCO is divided to by prescaler (32/33), 
    N counter in PLL IC. The internal phase comparator compares signal from the VCO with the 
    reference frequency. The regulator 5.8V increases the internal charge pump voltage of PLL IC. The 
    LPF contains C735, C734 and R718. This also reduces the residual side-band noise for the best 
    signal-to-noise ratio.
    Loop 
    filter
    VCTCXO
    +5V
    VCO
     VCO Control voltage CE
    CLOCK
    DATA
    STB
    Lock detector
    +5V +5.8V
    GND
    FLO CPO FIN-FIN VCC1 OSCIN
    GND CEGND
    CLOCK
    DATA
    LE
    FO/LD
    VCC2
    VP
    LMX2316 
    						
    							Audio and Control Circuit2-5
    3.5.3 Dual VCO
    The dual VCO module contains an RX VCO and a TX VCO. They are configured as Colpits 
    oscillators and connected to power through cascade buffers. Only one VCO is selected at a time. 
    The power source to each block is switched by transistors Q305 and Q111, and is dependent on the 
    states of TX_EN1 and RX_EN. The varicap diodes CR701 and CR702 produce a change in 
    frequency with a change in voltage. L703 and L706 are resonant tuning coils, which adjust the 
    operating frequency with specified DC tuning voltage applied. The audio signals from low pass filter 
    (U105-C) is applied to CR703 varicap diode in TX VCO to be modulated TX RF signal. 
    4.0 Audio and Control Circuit
    4.1 RX Audio
    The RX audio signal comes through the de-emphasis pass six order elliptic 300 Hz HPF and 3 order 
    300Hz HPF. This 300Hz High Pass Filter (U203) removes all signals under 300Hz to keep any 
    undesired signal from being heard from the speaker. After passing through this filter, audio signal is 
    de-emphasized by R209,C212 to get 6db/oct response. The de-emphasized audio signal passes 
    through volume control (SW/VOL1) and is amplified to a sufficient level to drive a loud speaker by 
    U601 Audio AMP. U601 has mute/un-mute function by the audio-mute control in CPU. If U601 pin 2 
    is low, the audio amplifier goes into active mode. If pin 2 is high, the IC goes into mute mode.
    TONE-FIL
    LPF AF-AMP
    HPF MIC MUTE
    MIC
    N/S SW
    U104-A U104-C
    Q109
    TONE-FIL  U202
    AUDIO-
    PATH
    Q103
    AF PA
    U601
    AUDIO-
    MUTEQ101
    to SPK.
    TONE-GEN.
    U104-D,
    U105-C U105
    MUTE-
    CON
    AUDIO-MUTE
    CON
    MOD. ADJ
    R159 6 Order
    Elliptic HPF 8 Order  LPF
    to CPU
    RX LOGIC
    3 Order HPF6 Order LPF 3 Order LPF
    to MOD.
    TX LOGIC
    +   3 Order HPF 260Hz
    From
    IF IC
    300Hz
    300Hz 3KHz
    SW/VOL1
    Q108
    De-EMPAUDIO-FIL U203
    300HzR209,C212 
    						
    							2-6Audio and Control Circuit
    4.2 RX Sub-Audible Decode Circuit
    The filter U202 is a 260Hz 8 order LPF to pass CTCSS, DCS signals and to block any other signals. 
    The signals that pass the LPF filter changes this sub-tone to logic signals in the Q208 pass 
    comparator (U202-D) so that the microprocessor can decode the CTCSS and DCS correctly. 
    4.3 TX Audio
    When the radio user pushes the PTT button, the microprocessor activates the entire transmitter 
    section, including the microphone. The audio signal from the microphone passes through the 3 
    order 300Hz high pass filter and through the limiting amplifier (U104-C, A) that has a 6db/oct pre-
    emphasis function. The pre-emphasized audio signal is adjusted to a proper level by R159 and 
    passes through a 6 order 3KHz low pass filter (U104-D,U105-C) before being modulated. Wide and 
    narrow channel spacing is controlled by the N/S switch (Q108).
    4.4 TX Sub-Audible Encode Circuit
    The encode circuit of CTCSS and CDCSS mixes signals from four ports of the microprocessor. This 
    mixed signal passes through 3 order 300Hz LPF (U105-B) to obtain clear CTCSS and DCS signals. 
    4.5 Microprocessor
    U101 controls all functions of the radio as a Microprocessor. It is operated by an external 
    7.3728MHz crystal. It detects external activities such as the pressing of the PTT, muting/un-muting 
    conditions, changing of channels, and then making the radio operate accordingly. 
    						
    							3-1
    Section 3VHF BAND 1 (136–150 MHZ) INFORMATION  
    						
    							3-2RF Circuit Board and Schematic Diagram for VHF Band 1 (136–150 MHz)1.0
    RF Circuit Board and Schematic Diagram for VHF Band 1 (136–150 MHz)
    VHF Band 1 (136–150 MHz) Main Board Top Side 
    						
    							RF Circuit Board and Schematic Diagram for VHF Band 1 (136–150 MHz)3-3
    VHF Band 1 (136–150 MHz) Main Board Bottom Side 
    						
    							3-4RF Circuit Board and Schematic Diagram for VHF Band 1 (136–150 MHz)VHF Band 1 (136–150 MHz) Schematic Diagram 
    						
    							4-1
    Section 4VHF BAND 2 (150–174 MHZ) INFORMATION (150–174 MHZ) 
    						
    							4-2RF Circuit Board and Schematic Diagram for VHF Band 2 (150–174 MHz)1.0 RF Circuit Board and Schematic Diagram for VHF Band 2 (150–174 MHz)VHF Band 2 (150–174 MHz) Main Board Top Side 
    						
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