400 - 512 MHz Base Station Data Radio Owner’s Manual Date Prepared: March 1, 2000 Document Control #: DC-95 Version: C-1 (Special Release) Copyright 2000-2002 IP MobileNet, Inc.
TABLE OF CONTENTS SECTION 1: THEORY OF OPERATION .................................................................................. 3 General Block Diagram ........................................................................................................... 3 General Block Diagram Definitions ................................................................................ 3 DR4B Base Station Data Radio Circuitry .......................................................................
SECTION 1: THEORY OF OPERATION General Block Diagram General Block Diagram Definitions For increased data security, the modem supports the U.S. Government developed Digital Encryption Standard (DES) data encryption and decryption protocols.
SECTION 1: THEORY OF OPERATION Modem Converts parallel data into an analog audio waveform for transmission and analog audio from the receiver to serial data. Serial data appears on the base station’s DB25 serial port. The radio supports a 115.2 KBPS data transmission rate on the serial port, SLIP protocol, and a 19.2 KBPS OR 9.6 KBPS over-theair data transmission rate.
SECTION 1: THEORY OF OPERATION DR4B Base Station Data Radio Circuitry The DR4B Base Station Data Radio works within the frequency range of 400-512 MHz. The following section provides detail views, descriptions, and key areas on the DR4B Base Station Data Radio circuit board especially useful during troubleshooting. System Controller This section displays the Central Processing Unit (CPU)(U1), clock, and power-on reset circuitry.
SECTION 1: THEORY OF OPERATION Modem Switching This section displays the connector wiring and modem switching circuitry. Connector J2 is routed to the front-panel TX, CD, and RX1-RX3 LED indicators. The radio will also accept modulation from an external source (modem or amplified microphone audio). Modem This base station uses separate modems for receive and transmit functions so that full-duplex operation may be obtained.
SECTION 1: THEORY OF OPERATION example, if a fault in the base station site produces a contact closure on one of the alarm inputs, the radio transmits a fault message to the Communication Center. Examples of faults include site door open, high temperature, high VSWR, etc. Upon receipt of the fault message, a technician is dispatched to the base station site to correct the fault.
SECTION 1: THEORY OF OPERATION Baseband This circuitry amplifies the audio from each receiver, routes it through solid-state switches, and selects the audio from the receiver with the highest quality value. The comparator circuit on the previous sheet controls it. There are three (3) channels of audio, with separate gain and DC offset adjustments to compensate for performance differences in the receivers. For example, incoming audio from receiver 1 appears at AUDIO 1.
SECTION 1: THEORY OF OPERATION IF Amplifier The incoming 45 MHz signal passes through Y5, a highly selective monolithic bandpass filter. From there the IF signal passes through an LC matching network. C17, C18, C24, and L5 provide impedance matching to the IF amplifier input. U6 is a super heterodyne IF subsystem. Inside the chip, the signal is applied to a mixer. The mixer also accepts a 44.545 MHz local oscillator input.
SECTION 1: THEORY OF OPERATION This section displays the DC power supplies, frequency reference, and RF output circuitry. Regulator VR1 provides 9 volts DC for VCO module VCO1, and RF amplifier (U7). Regulator (VR2) provides a low noise 5-volt DC output for inverter (U3), synthesizer (U2), and reference (Y1). Reference module (Y1) provides a high-stability 10 MHz reference frequency. Y1 is a voltage controlled, temperature controlled crystal oscillator (VCTCXO).
SECTION 1: THEORY OF OPERATION the VCO, canceling out most of the modulation. The output from the jumper block goes to the 10 MHz reference via REFMOD. The VBIAS input is a 2.5-volt DC source, which biases the op amps to the correct operating point. It is generated by modem chip (U14) on the System Controller Board. Phase Locked Loop This section displays phase locked loop (PLL) circuitry. The 10-MHz reference (Y1), runs synthesizer (U2), which in turn controls VCO1.
SECTION 2: FACTORY TEST PROCEDURE Equipment List The following table lists the equipment required to perform the DT450 Mobile Data Radio Factory Test Procedure: QTY 2 1 DESCRIPTION MANUFACTURER PC’s One for Mobile One for Base Service Monitor – Communication Test Set Windows 9X w/ IPMessage AVR 1 Digital multi-meter 1 DC power supply w/ ammeter, 13.
SECTION 2: FACTORY TEST PROCEDURE Programming and Configuring the Base Station Data Radio Once the appropriate equipment for performing the factory test are gathered, perform the following steps to rpgoram and configure the DR4B Base Station Data Radio: Step 1 Enter the following information on the Base Station Data Radio Performance Test Data Sheet: Base Station Serial number Date test being performed Tester’s name Step 2 At the HyperTerminal window, type in the appropriate password and press [EN
SECTION 2: FACTORY TEST PROCEDURE Adjustment / Alignment Procedures Receiver Injection Perform the following steps to adjust the receiver injection and injection frequency: Step 1 Using the HP high frequency probe, verify that the receiver injection frequency is present at each of the three (3) receivers by monitoring the receivers’ R12 surface mount pad which lies on the 50 ohm track between L3 and U3.6.
SECTION 2: FACTORY TEST PROCEDURE Step 5 Inject an on-frequency signal at a level equal to Receiver 2 12dB SINAD level, modulated with a 1 KHz test tone at ±5.0 KHz deviation into Receiver 2. Step 6 While monitoring TP2 with the digital multi-meter, adjust RSSI2 low adjust potentiometer (R10) for a reading of 0.750 VDC ±10 mV. Step 7 Increase the amplitude of the signal by 50 dBm.
SECTION 2: FACTORY TEST PROCEDURE Exciter Step 1 Using the X=2000,19 command, generate data messages so the transmit power and frequency can be checked. Step 2 Connect the base stations' transmit port to the HP communication test set. Note the power level prior to adjusting. Step 3 On the power amplifier circuit board adjust the potentiometer (RV1) fully clockwise (this will enable low power transmit operation).
SECTION 3: FCC LABEL DR4B Base Station Data Radio FCC Label Placement DR4B Base Station Data Radio FCC Label Placement ~\Technical Documentation\System Manuals\FCC-Reports\DR4B-FCCRpt.
APPENDIX B: DR4B CIRCUIT BOARD DIAGRAM ~\Technical Documentation\System Manuals\FCC-Reports\DR4B-FCCRpt.
