Operational Description

FCC ID: Q5EPT800003

Operational Description

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FCCID_1029938

DESCRIPTION EMITTER DESCRIPTION Product Name： Mobile Radio Model Number： PT8000-03 1. Emitter Power Voltage: DC 13.6V 2. CPU Frequency: 7.3MHz 3. Emissive Frequency: 438MHz-490MHz Modulating manner: FM 4.Work process: There is a PTT (Push-To-Talk) button. Press this button, then speak into the microphone to send signal. Release the button to receive. 5 RECEIVER WORKING PROCESS An incoming signal from the antenna is applied to a RF amplifier (Q18) after passing through a transmit/receive switch circuit (D3、D11) and a 2-pole LC filter. After the signal is amplified (Q18), the signal is filtered by a band pass filter (a 3-pole LC tuner filter) to eliminate unwanted signals before it is passed to the first mixer. The tuner voltage of these diodes are controlled by to track the MCU(IC11). 5.1 First Mixer The signal from the RF amplifier is heterodyned with the first local oscillator signal from the PLL frequency synthesizer circuit at the first mixer (Q19) to create a 49.95MHz first intermediate frequency (1st IF) signal. The first IF signal is then fed through a monolithic crystal filters (MCFs: XF 1&XF2) to further remove spurious signals. 5.2 IF amplifier The first IF signal is amplified by Q20, and then enters IC6(FM processing IC) .The signal is heterodyned again with a second local oscillator signal within IC6 to create a 450KHz second IF signal. The second IF signal is then fed through a 450KHz ceramic filter (CF1/CF2) to further eliminate unwanted signals before it is amplified and FM detected in IC6. 5.3 AF amplifier The recovered AF signal obtained from IC6 is filtered by the baseband processor IC9. The processed AF signal passes through an AF volume control and is amplified to a sufficient level to drive a loud speaker by an AF power amplifier (IC7). 6 Transmitter 6.1 Transmit audio The modulation signal from the microphone is amplified by IC13, passes through a pre-emphasis and amplified by the baseband processor IC13 to perform IDC operation. The resulting signal goes to the VCO through the VCO modulation terminal for direct FM modulation. 6.2 VCO and RF amplifier The transmit signal obtained from the VCO buffer amplifier Q1, is amplified by Q2、Q4 and Q5. This amplified signal is passed to the power amplifier IC 1, amplifier producing up to 25W of RF

power. 6.3 ANT switch and LPF The RF amplifier output signal is passed through a low pass filter network and a transmit/receive switching circuit before it is passed to the antenna terminal. The transmit/receive switching circuit is comprised of D3 and D11. are turned on (conductive) in transmit mode and off (isolated) in receive mode.


Document Created: 2008-10-23 17:21:03
Document Modified: 2008-10-23 17:21:03
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