Circuit Description

FCC ID: K66VX-4000UE

Operational Description

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FCCID_130475

headphone jack or 4-ohm loudspeaker. Circuit Description PLL synthesizer The 1st LO maintains stability from the PLL synthesizer Reception and transmission are switched by “RX” and ” by using a 14.500 MHz reference signal from crystal TX” lines from the microprocessor unit (MPU). The X1001. PLL synthesizer IC Q1024 (SA7025DK) consists receiver uses double-conversion superheterodyne of a prescaler, reference counter, swallow counter, circuitry, with a 43.95MHz 1st IF and 450 kHz 2nd IF. The programmable counter, a serial data input port to set 1st LO, produced by a PLL synthesizer, yields the these counters based on the external data, a phase 43.95MHz 1st IF. comparator, and charge pump. The PLL-IC divides the The 2nd LO uses a 43.5 MHz (43.95 MHz-450 kHz) 14.500 MHz reference signal by 725 using the reference signal generated by a crystal oscillator. The 2nd mixer counter (20.0 kHz comparison frequency). The phase and other circuits use a custom IC to convert and amplify detector comparison frequency to be eight times the the 2nd IF, and detect FM to obtain demodulated signals. channel spacing (2.5kHz). The VCO output is divided by During transmit, the PLL synthesizer oscillates at the the prescaler, swallow counter and programmable desired frequency directly, for amplification to obtain RF counter. These two signals are compared by the phase power output. During transmit, voice modulation and comparator and input to the charge pump. A voltage CTCSS (or DCS) modulation are applied to this proportional to their phase difference is delivered to the synthesizer. Transceiver functions, such as TX/RX low-pass filter circuit, then fed back to the VCO as a control, PLL synthesizer settings, and channel voltage with phase error, controlling and stabilizing the programming, are controlled using the MPU. oscillating frequency. This synthesizer also operates as a modulator during transmit. The RX-VCO is comprised of Q1015 (2SK520) and VHF D1017, D1018, D1035, D1036 (HVU356x4), and oscillates between 177.950MHz and 217.950MHz Receiver according to the programmed receiving frequency. And Incoming RF signals from the antenna connector are the TX-VCO is comprised of Q1014 (2SC5107) and delivered to the MAIN Unit, and pass through a low-pass D1015, D1016, D1019 (1SV276x3), and oscillates filter (LPF) antenna switching network consisting of coils between 134.000MHz and 174.000MHz according to the L1001, L1002, L1003 and L1006, capacitors programmed transmit frequency. The VCO output C1001,C1006, C1009, C1013, and C1023, and antenna passes through buffer amplifier Q1018 (2SC5107), and a switching diodes D1006,D1007 and D1008 for delivery to portion is fed to the buffer amplifier Q1019 (2SC5107) of the receiver front end. the PLL IC, and at the same time amplified by Q1021 Signals within the frequency range of the transceiver are (2SC5107) to obtain stable output. The VCO DC supply then passed through a varactor-tuned bandpass filter is regulated by Q1008 (2SC4154E). Synthesizer output is consisting of L1008, L1009 / L1024, L1025 before RF fed to the 1st mixer by diode switch D1024 (1SS321) amplification by Q1012 (3SK228). during receive, and to drive amplifier Q1020/Q1022 The amplified RF is then band-pass filtered again by (2SC5415Ex2) for transmit. The reference oscillator varactor-tuned resonators L1018, L1019 / L1038, L1039 feeds the PLL synthesizer, and is composed of crystal to ensure pure in-band input to 1st mixer X1001 (14.500 MHz), the temperature compensation Q1025(2SK228). circuit which includes D1033 (MC2850) and thermostats Buffered output from the VCO Unit is amplified by TH1003 and TH1002, and transmit (DCS) modulation Q1021 (2SC5107) and low-pass filtered by L1042 / circuit D1029 (1SV2309). L1046 and C1132 / C1139 / C1142, to provide a pure 1st local signal between 112.3 and 152.3 MHz to the 1st Transmitter mixer. Voice audio from the microphone is delivered via the The 43.95MHz 1st mixer product then passes through Mic (Jack) Unit to the MAIN Unit, after passing through dual monolithic crystal filters XF1001 and XF1002 (7.5 amplifier Q3039/Q2108 (NJM2902V), pre-emphasis, kHz BW), and is amplified by Q1029 (2SC4215Y) and limiter (IDC instantaneous deviation control) ,and LPF delivered to the input of the FM IF subsystem IC Q1026 Q2001 (NJM2902V), is adjusted for optimum deviation (TA31136FN). level and delivered to the next stage. This IC contains the 2nd mixer, 2nd local oscillator, Voice input from the microphone and CTCSS are FM- limiter amplifier, FM detector, noise amplifier, and modulated to the VCO of the synthesizer, while DCS squelch gates. audio is modulated by the reference frequency oscillator The 2nd LO in the IF-IC is produced from crystal X1001 of the synthesizer. (14.500MHz), and the 1st IF is converted to 450kHz by Synthesizer output, after passing through diode switch the 2nd mixer and stripped of unwanted components by D1024 (1SS321), is amplified by driver Q1020 / Q1022 ceramic filter CF1001 or CF1002. After passing through a (2SC5415Ex2) and power module Q1013 (M67746) to limiter amplifier, the signal is demodulated by the FM obtain full RF output. The RF energy then passes through detector. antenna switch D1007 / D1008 and a low-pass filter Demodulated receive audio from the IF-IC is amplified by circuit and finally to the antenna connector. Q1031 (2SA1602A) / Q2014 (CXA1846N). After volume RF output power from the final amplifier is sampled by adjustment by the AF power amplifier Q2029 CM coupler and is rectified by D1011, D1014 (TDA7240AV), the audio signal is passed to the optional

(HSM88ASx2). The resulting DC is fed through kHz BW), and is amplified by Q1029 (2SC4215Y) and Automatic Power Controller Q1007 (NJM2904V), Q1001 delivered to the input of the FM IF subsystem IC Q1026 (2SC4154E), Q1002 (2SB1143S) to transmitter RF (TA31136FN). amplifier and thus the power output. This IC contains the 2nd mixer, 2nd local oscillator, Generation of spurious products by the transmitter is limiter amplifier, FM detector, noise amplifier, and minimized by the fundamental carrier frequency being squelch gates. equal to the final transmitting frequency, modulated The 2nd LO in the IF-IC is produced from crystal X1001 directly in the transmit VCO. Additional harmonic (14.500MHz), and the 1st IF is converted to 450kHz by suppression is provided by a low-pass filter consisting of the 2nd mixer and stripped of unwanted components by L1002, L1003, L1007, L1012 and C1006, C1009, C1013, ceramic filter CF1001 or CF1002. After passing through a C1023, C1033, C1037 and C1046, resulting in more than limiter amplifier, the signal is demodulated by the FM 60dB of harmonic suppression prior to delivery to the RF detector. energy to the antenna. Demodulated receive audio from the IF-IC is amplified by Q2014 (CXA1846N). After volume adjustment by the DCS Demodulator AF power amplifier Q2029 (TDA7240AV), the audio DCS signals are demodulated on the MAIN-UNIT, and signal is passed to the optional headphone jack or 4-ohm are applied to low-pass filter Q2110 (NJM2902V), as well loudspeaker. as the limiter comparator Q2110. PLL synthesizer CTCSS encoder/decoder The 1st LO maintains stability from the PLL synthesizer The CTCSS code is generation and encoding by MPU IC by using a 14.500 MHz reference signal from crystal Q2019 (MB90F583B). X1001. PLL synthesizer IC Q1024 (SA7025DK) consists Demodulation and detection of the CTCSS tones are of a prescaler, reference counter, swallow counter, carried out by IC Q2013 (MX165C). programmable counter, a serial data input port to set these counters based on the external data , a phase MPU comparator, and charge pump. The PLL-IC divides the Operation is controlled by 16-bit MPU IC Q2019 14.500 MHz reference signal by 725 using the reference (MB90F583B). The system clock uses a 16.000 MHz counter (20.0 kHz comparison frequency). The phase crystal for a time base. IC Q2027 (S-80735SN) resets the detector comparison frequency to be eight times the MPU when the power is on, and monitors the voltage of channel spacing (2.5kHz). The VCO output is divided by the regulated 5V power supply line. the prescaler, swallow counter and programmable counter. These two signals are compared by the phase EEPROM comparator and input to the charge pump. A voltage The EEPROM retains TX and RX data for all memory proportional to their phase difference is delivered to the channels and CTCSS data, DCS data, prescaler dividing, low-pass filter circuit, then fed back to the VCO as a and REF oscillator data (internal/external). voltage with phase error, controlling and stabilizing the oscillating frequency. This synthesizer also operates as a modulator during transmit. The RX-VCO is comprised of Q1015 (2SK508) and D1017, D1018 (1SV276x4), and oscillates between UHF 356.050MHz and 468.050MHz according to the programmed receiving frequency. And the TX-VCO is Receiver comprised of Q1014 (2SC4226) and D1015, D1016, Incoming RF signals from the antenna connector are D1019 (1SV276x2, 1SV230), and oscillates between delivered to the MAIN Unit, and pass through a low-pass 400.000MHz and 512.000MHz according to the filter (LPF) antenna switching network consisting of coils programmed transmit frequency. The VCO output L1001, L1002, L1003,L1004 and L1005, capacitors passes through buffer amplifier Q1018 (2SC5107), and a C1004, C1008,C1009, C1011, and C1014, and antenna portion is fed to the buffer amplifier Q1019 (2SC5107) of switching diodes D1006,D1007 and D1008 for delivery to the PLL IC, and at the same time amplified by Q1021 the receiver front end. (2SC5107) to obtain stable output. The VCO DC supply Signals within the frequency range of the transceiver are is regulated by Q1008 (2SC4154E). Synthesizer output is then passed through a varactor-tuned bandpass filter fed to the 1st mixer by diode switch D1024(1SS321) consisting of L1009, L10014 before RF amplification by during receive, and to drive amplifier Q1020 (2SC5107) / Q1012 (2SK4227). Q1022 (2SC5415E) / Q1031 (2SC2954) for transmit. The The amplified RF is then band-pass filtered again by reference oscillator feeds the PLL synthesizer, and is varactor-tuned resonators L1022, L1026 to ensure pure composed of crystal X1001 (14.500 MHz), the in-band input to 1st mixer Q1025 (2SK228). temperature compensation circuit which includes D1033 Buffered output from the VCO Unit is amplified by Q1021 (MC2850) and thermostats TH1003 and TH1002, and (2SC5107) and low-pass filtered by L1030 / L1031 and transmit (DCS) modulation circuit D1029 (1SV230). C1178 / C1180 / C1182, to provide a pure 1st local signal between 112.3 and 152.3 MHz to the 1st mixer. Transmitter The 43.95MHz 1st mixer product then passes through Voice audio from the microphone is delivered via the dual monolithic crystal filters XF1001 and XF1002 (7.5 Mic (Jack) Unit to the MAIN Unit, after passing through

amplifier Q3039/Q2108 (NJM2902V), pre-emphasis, limiter (IDC instantaneous deviation control) ,and LPF Q2001 (NJM2902V), is adjusted for optimum deviation level and delivered to the next stage. Voice input from the microphone and CTCSS are FM- modulated to the VCO of the synthesizer, while DCS audio is modulated by the reference frequency oscillator of the synthesizer. Synthesizer output, after passing through diode switch D1024 (1SS321), is amplified by driver Q1020 (2SC5107) / Q1022 (2SC5415E) / Q1031 (2SC2954) and power module Q1013 (M68759) to obtain full RF output. The RF energy then passes through antenna switch D1007 / D1008 and a low-pass filter circuit and finally to the antenna connector. RF output power from the final amplifier is sampled by CM coupler and is rectified by D1011,D1014(HSM88ASx2). The resulting DC is fed through Automatic Power Controller Q1007 (NJM2904V), Q1001 (2SC4154E), Q1002 (2SB1143S) to transmitter RF amplifier and thus the power output. Generation of spurious products by the transmitter is minimized by the fundamental carrier frequency being equal to the final transmitting frequency, modulated directly in the transmit VCO. Additional harmonic suppression is provided by a low-pass filter consisting of L1001, L1003, L1004 and C1004, C1008, C1009, C1011 and C1014, resulting in more than 60dB of harmonic suppression prior to delivery to the RF energy to the antenna. DCS Demodulator DCS signals are demodulated on the MAIN-UNIT, and are applied to low-pass filter Q2110 (NJM2902V), as well as the limiter comparator Q2110. CTCSS encoder/decoder The CTCSS code is generation and encoding by MPU IC Q2019 (MB90F583B). Demodulation and detection of the CTCSS tones are carried out by IC Q2013 (MX165C). MPU Operation is controlled by 16-bit MPU IC Q2019 (MB90F583B). The system clock uses a 16.000 MHz crystal for a time base. IC Q2027 (S-80735SN) resets the MPU when the power is on, and monitors the voltage of the regulated 5V power supply line. EEPROM The EEPROM retains TX and RX data for all memory channels and CTCSS data, DCS data, prescaler dividing, and REF oscillator data (internal/external).


Document Created: 2000-07-14 01:21:33
Document Modified: 2000-07-14 01:21:33
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