Base Station and Repeater Technical Manual SMX920
Technical Manual SMX920 Base Station & Repeater RELM Wireless Corporation 7100 Technology Drive West Melbourne, FL 32904 Front Desk: (321) 984-1414 Sales: (800) 821-2900 Service: (800) 422-6281 www.relm.com Manual Revision 08-05 In order to continually improve our products, Spectra Engineering Pty Ltd and RELM Wireless Corporation reserves the right to alter, without notice and at any time, the equipment and specifications described in this document.
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Technical Manual SMX920 Base Station & Repeater Record Of Changes Any changes to this manual are recorded on this list. RELM Wireless may issue replacement pages to you from time to time. If any updates are issued, you will also receive a replacement for this page. Date Version Chapter Changes Pages Changed Mar 2003 1.0.0 All - Initial Release All June 2004 1.1.0 General Revision All Sept 2004 1.1.
SMX920 Base Station & Repeater Technical Manual SAFETY SUMMARY Only the SMX920’s self contained power supply, if installed, contains dangerous mains voltages within. Normal operation and use of the SMX920 does not expose the operator or service technician to high voltage parts. The power supply is isolated from and maybe removed safely from the main chassis. For servicing, please return to your nearest distributor. No fuses or user-serviceable parts are within the power supply module.
Technical Manual Table of Contents Table of Contents 1. General Description........................................................................................... 1 1.1 Physical Description.................................................................................. 2 1.1.1 Front Panel .................................................................................. 3 1.2 Module Functional Description................................................................. 6 1.2.
SMX920 Base Station & Repeater 6.4 6.5 vi Technical Manual 6.3.2 RX Front End ............................................................................. 22 6.3.3 IF Section ................................................................................... 22 Exciter Module........................................................................................ 23 6.4.1 VCO Locking .............................................................................. 23 6.4.2 RF Power........................
Technical Manual Table of Contents List of Tables Table 1-1 LED Functions ................................................................................................ 4 Table 1-2 Rear Panel Connections.................................................................................. 5 Table 2-1 Micro Controller Jumper ................................................................................ 9 Table 5-1 Microprocessor Port Parameters...............................................................
SMX920 Base Station & Repeater Technical Manual List of Figures Figure 1-1 SMX920 Horizontal andVvertical types of Front Panel LEDs....................... 3 Figure 1-2 SMX920 Rear Panel with Power Supply and Duplexer fitted. ...................... 5 Figure 7-1 Under (increase level) ................................................................................. 29 Figure 7-2 Over (decrease level)...................................................................................
Technical Manual 1. General Description The SMX920 series employs state of the art design and construction methods to deliver a range of high performance, very reliable radio base stations and repeaters. They are ideally suited for use in VHF or UHF two-way voice communications radio systems.
SMX920 Base Station & Repeater Technical Manual ♦ Built in diagnostics ♦ Built in community multi-tone style repeater ♦ CTCSS, Full duplex DCS, 5 tone, local speaker and many other options included as standard ♦ Programmable channel spacing ♦ Low receiver standby current consumption ♦ Flash upgradeable In addition, the SMX920 can be fitted with options, not being limited to the following: ♦ Simplex antenna changeover relay ♦ Power supply ♦ Duplexer ♦ Batteries for power backup system ♦
Technical Manual Installation and Operation 1.1.1 Front Panel 1.1.1.1 Standard Front Panel The SMX920 front panel comes in both horizontal and vertical types, this can be see in the illustrated below. The front panel provides the user with real time status of the SMX920. Figure 1-1 SMX920 Horizontal andVvertical types of Front Panel LEDs ♦ Microphone /Accessory Socket An RJ45 socket is provided on the front panel for connection of a microphone.
SMX920 Base Station & Repeater Technical Manual incoming signals will override the Squelch and be heard in the speaker. When CTCSS is enabled the channel remains quiet until someone transmits using the same tone. Should the receiver be setup for the reception of a signalling tone, the 'Green RX LED' lamp with be on, also if it contains the correct tone the 'Yellow Tone LED' lamp will be lit, and audio out of the speaker will then be heard. When the transmission ends, the channel becomes quiet again.
Technical Manual 1.1.1.2 Installation and Operation Rear Panel The rear panel image shown has the internal Power supply fitted, alternatively the SMX920 can be ordered without the Power Supply or it can be retrofitted at a later date should this be required. In the case of power being fed externally, the flying lead is then routed out through the cable clamp grommet supplied with all units. No change to the wiring in this case is required.
SMX920 Base Station & Repeater Technical Manual 1.2 Module Functional Description 1.2.1 RF Module and Main Controller Assembly The SMX920 consists of a full duplex RF module with its own shielded metal housing and a Main Controller board integrated on a single PCB. Using advanced yet simplified circuit designs, the size and complexity is reduced.
Technical Manual Installation and Operation An on onboard EEPROM stores all of the user channel related data such as frequencies, CTCSS tones etc. A serial port at the Microphone accessory socket of the SMX920 provides access to the Controller card software configurations for the purpose of the user to create and change this channel related information.
SMX920 Base Station & Repeater Technical Manual 2. Installation and Operation 2.1 Installation SMX920 series radios are securely packed for transport with special packers within a cardboard container. Before unpacking the SMX920 radio, please inspect the packaging for signs of damage and report any damage to your SMX920 distributor. Upon unpacking of the SMX920 radio, please ensure that all items shipped were received, report any missing items to your SMX920 distributor.
Technical Manual Installation and Operation Table 2-1 below summarises the functions of the jumper. JMP Function / Description Default Selection Default Position JMP 1 / CNVSS Selects either default single chip mode or microprocessor mode for the microcontroller. Single chip mode ON Table 2-1 Micro Controller Jumper 2.2.1.2 Select Operating Mode The SMX920 can operate in a number of different modes. The primary alternatives are full duplex, which is the default mode, repeater and simplex.
SMX920 Base Station & Repeater 2.2.1.5 Technical Manual Configure Accessory Button The Front Panel Accessory Button can be software configured to perform a number of functions such as tone encoder call, cancel function for tone decoder and alarm clear. Please refer to the radio configuration menu system for additional setup information. The exact functionality and available features will also depend upon the firmware version installed. 2.2.
Technical Manual Installation and Operation 3. Standard Features 3.1 Programmable Channel Spacing The SMX920 receiver can be programmed for either 12.5 kHz (Narrow Band) or 25 kHz (Wide Band) channel bandwidth. Switchable IF filters in the receiver and automatic 12.5 kHz / 25 kHz gain compensation in the audio paths make the change in bandwidth transparent to the user. With the switchable IF bandwidth receiver, each channel is programmed as either 12.5 kHz / 25 kHz via the Channel Edit screen. 3.
SMX920 Base Station & Repeater ♦ Technical Manual Channel Change Control Twin push wheel switches are fitted to the front panel to allow selection of the operating channel. When fitted this switch is wired to the channel select pins on SKC. 99/100 channels are selectable. Refer to Section 2.2.1.3 for more details on alternative channel select methods. SMX920 Testing: 1. Connect a Communications Cable to the SMX920. 2. Set SMX920 into Diagnostics mode using the built-in radio configuration menu system.
Technical Manual Installation and Operation 4. Options Due to ongoing development please refer to www.RELM.com for the latest revision of options . 4.1 Simplex Changeover Relay 4.1.1 Description For simplex applications an internally mounted coaxial changeover relay can be provided. This mounts on the rear panel and the common port protrudes through the chassis providing the simplex antenna connection.
SMX920 Base Station & Repeater Technical Manual SMX920 Controller Setup: 1. The SMX920 RF channels that are required to be simplex should be programmed as ‘SIMPLEX’ within the channel edit screen of the radio configuration menu system and then downloaded to the SMX920. 2. Software switch ‘Simplex mode’ in the radio configuration menu system is switched ‘X’ as per Section 4.1 of the SMX920 Manual. SMX920 Testing: 1. Connect a Communications Test Set to the SMX920. 2.
Technical Manual Installation and Operation 5. Technical Description The internal design of the SMX920 is of a modular nature allowing for simple configuration and maintenance while ensuring minimal downtime. 5.1 Exciter Section RF from the VCO is at a nominal level of +3 dBm is applied to the fractional-N synthesiser main divider input.
SMX920 Base Station & Repeater Technical Manual and VF processing. The Received Signal Strength Indication (RSSI) is buffered and connected to the Micro Controller. RF from the VCO at a nominal level of +3 dBm is applied to the fractional-N synthesiser’s main divider input. This signal is compared with the reference oscillator frequency and the correction voltage from the synthesiser’s charge pump output is filtered then amplified by the non inverting low noise op amp.
Technical Manual Installation and Operation The FX828 (IC29) is a flexible predictive or non-predictive, full duplex CTCSS / Selcall encoder / decoder, DCS decoder, which is under the control of the microprocessor. 5.2.2 TX Signal Processing TX audio may be sourced from a number of different paths. These include Talk through audio, microphone and tone generators (ie Selcall, DTMF, DCS, CTCSS under micro controller control.
SMX920 Base Station & Repeater Technical Manual 5.2.4 RF Power Control Forward power is controlled by the microprocessor through two mechanisms. Based on pre-programmed per channel adjustments the microprocessor sets the digital to analog converter output to a reference setting. IC28B serves as a comparator and, with the non-inverting input connected to the output of the digital to analog converter, is set up with a reference voltage.
Technical Manual Installation and Operation A dual directional coupler consists of coupled microstrip transmission lines fabricated on the PCB artwork. The sampled RF energy is rectified to provide a proportional DC voltage output. The PTT signal enables the amplifier circuit by providing bias to the transistors. A thermistor TS1, physically located on the PA heatsink monitors the heatsink’s temperature and is monitored by the Micro Controller.
SMX920 Base Station & Repeater Technical Manual 6. SMX920 Base Station Fault Finding Procedure The following test equipment may be required for the following tests: ♦ SMX920 in built Base Station Programming Utility ♦ RF Test Set (eg HP 8920 or equivalent) ♦ CRO (Cathode Ray Oscilloscope) ♦ RF Power Meter (capable of measuring to 60 Watts continuously) ♦ Multimeter ♦ +13.8V DC Power Supply (capable of supplying 15Amps) ♦ SMX920 test jig (Optional) 6.
Technical Manual Installation and Operation ♦ If the Diagnostics shows abnormal, then check the voltage on pin 95 of IC1 on the Control Board. If the voltage is low ie <200mV then the likely fault is IC1. If the voltage is >200mV then the likely fault is within the PA module. ♦ If the Diagnostics shows normal, then check the RF level from the Exciter section by connecting a Power Meter directly to the Exciter RF connector.
SMX920 Base Station & Repeater Technical Manual 6.2 Microcontroller Section of PCB Check fuse. If blown, replace with a 5x20 mm 3A fast blow fuse. Check jumper is in the correct position for operation. 6.3 Receiver Section 6.3.1 VCO Locking ♦ Using the in-built menu, check all Hardware settings are correct. ♦ Check the value of X9 (13 MHz) is the same as the Rx Reference Freq. in the ‘Hardware Settings’ using the in-built menu system .
Technical Manual Installation and Operation ♦ Adjust the TCXO to within +/- 20Hz. ♦ If the RX centre frequency cannot be adjusted the TCXO may be faulty. ♦ Distortion should be less than 3%. ♦ If the distortion is high then FL3A, FL3B or FL4 may be faulty. ♦ If the sensitivity is still poor then return the Module to your Service Centre. 6.4 Exciter Module 6.4.1 VCO Locking ♦ Check the reference frequency of X2 (13 MHz) is the same as the TX Reference Freq.
SMX920 Base Station & Repeater 24 Technical Manual ♦ With PTT ON measure the PA bias current at the Gates of the FET’s. The Bias current is band dependent. This is done by monitoring the current drain of the whole PA with CN1 disconnected. Link the gate of TR2 to GND. Measure current consumption (VHF High Band 200mA ,UHF 400mA.) This can be adjust by RV2. Measure gate volts ≈ 3.4V Remove link from TR2. Measure current consumption, adjust RV1 so that current is 2Amp total (VHF & UHF).
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SMX920 Base Station & Repeater Technical Manual 7. Alignment and Testing The SMX920 test and alignment section assumes that the radio is a working module. Due to ongoing development the instructions may vary please refer to www.RELM.com for updates. 7.1 Transceiver Setup, Calibration and Alignment This section explains how to setup, calibrate and align the complete SMX920 Base Station. A number of procedures are required to fully initialise the SMX920.
Technical Manual Installation and Operation When setting up the radio it is recommended that all measurement and adjustments are done on a channel that is in the centre of the frequency spread of the channels. This minimises any errors due to frequency changing. Alternatively if the frequency spread of the channels is too large then you may wish to calibrate and align every channel. (In most cases this will not be necessary). Both individual and group alignment will be covered.
SMX920 Base Station & Repeater Technical Manual 2060-ohm resistor between pins 4 and 6 of this connector of the SMX920 Base Station. Temperature calibration is done via the Calibration Screen. To complete the temperature calibration, follow the instructions that in built menu system provides. 7.1.8 TX Power Adjustment The transmitter power setup is used to set the correct power for each channel. This can be done on a per channel basis or all channels can be set at once. 7.1.
Technical Manual Installation and Operation Examples of incorrect, observed waveforms are as follows: Figure 7-1 Under (increase level) Figure 7-2 Over (decrease level) The waveform when correctly aligned should look as follows: Figure 7-3 Correctly Aligned Waveform Choose ‘OK’ to accept the changes made. This then saves the changes that you have made to the radio.
SMX920 Base Station & Repeater Technical Manual Bandwidth FM Nominal Deviation (kHz) FM Peak Deviation (kHz) Narrow (12.5kHz spacing) 1.5 2.4 Wide (25kHz spacing) 3.0 4.8 Table 7-2 Nominal Deviation The radio is defaulted to work in this Nominal mode. The radio also can operate in a peak deviation mode. To change mode use the built in menu system. Configuration Menu --Software Switch Configuration Menu-- Nominal / Peak deviation . 7.1.
Technical Manual Installation and Operation 8. Appendices 8.1 SMX920 Interface Connections The user connections to the SMX920 are all made via the Front and rear panel where the following connectors are located. No Conn Type Function Description CN6 N TYPE Simplex relay out or N type RX input Location for internal simplex relay. The antenna for RX / TX connects to this point.
SMX920 Base Station & Repeater Technical Manual 8.1.1 CN6 Simplex Relay This option maybe also pre-installed or retrofitted at a later date. The N type connector for the RX port is removed and the relay is mounted in it’s position, which then acts as the RF I/O port for simplex operation. When this option is installed the radio programming will required to be change to reflect the simplex mode. 8.1.2 CN7 TX Output This is an N type connector used as the TX RF power output. 8.
Technical Manual Installation and Operation 8.3 Establishing RS232 Communications In this section we will look at how to connect your personal computer (PC) to the SMX920, allowing access to the powerful inbuilt menu system. The RS232 programming port is part of the front Panel Microphone accessory socket. You will be required to make a RS232 cable to be able to communicate with the in built menu system software in the SMX920.
SMX920 Base Station & Repeater Technical Manual Figure 8-2 Front veiw of DB9 female connector and RJ45 Modular male connector Figure 8-3 RS232 Cable 8.3.1 Software Menu System The SMX920 Desktop Repeater comes with its own internal menu system accessed with any general terminal package. The menu system allows the user to change several configuration settings to suit the environment in which the SMX920 must operate. The menu system is entered through a terminal emulator program.
Technical Manual Installation and Operation 8.3.2 Interfacing Information The RS-232 signal on a single cable is impossible to screen effectively for noise. By screening the entire cable we can reduce the influence of outside noise, but internally generated noise remains a problem. So when an audio connection and a RS232 Control are required at the same time, use a double adaptor RJ45 socket (Figure 1-1).
SMX920 Base Station & Repeater Technical Manual 8.4.2 General Parameter Specification SMX920 Rack Size: 3RU Tray, 330mm deep including fan. SMX920 Overall Physical Size 89mm high, 360mm deep, 483mm wide Weight < 9 kg Supply Voltage: 13.8V +/- 20%. Power Consumption: <400mA receive, typical 360mA. (TX VCO off). <10A for 50W TX RF @13.8VDC. Operating Temperature: -30 to +60 C. Individual Module Dimensions: Main board W=260, L=227, H = 35mm. PA W=78, L=300, H = 60mm.
Technical Manual Installation and Operation 8.4.3 Transmit Measured in accordance with TIA/EIA-603 standards. Parameter Specification RF Power Output: 1W to 50W Frequency Stability: > 300 MHz < 300 MHz 1.5PPM for –10 to 60C, 2.5PPM for –30 to –10C 2.5PPM for –10 to 60C, 5PPM for –30 to –10C. Audio response: Flat within +1, -3 dB across bandwidth Audio Bandwidth VF input: 300 Hz to 3000 Hz Bessel LPF Modulation Distortion: Less than 3% at 60% deviation. S/N Ratio: Better than 46 dB, wide band.
SMX920 Base Station & Repeater Technical Manual 8.4.4 Receive Measured in accordance with TIA/EIA-603 standards. Parameter Specification Sensitivity: Better than –117 dBm for 12 dB SINAD. Typical –120 dBm. Selectivity 135-520MHz: More than 85 dB for 25 kHz adj channel. More than 75 dB for 12.5 kHz adj channel. Spurious Resp: Better than 80 dB. Intermodulation: Better than 80 dB. Blocking: Better than 100 dB at +/- 1 MHz point. Co-Channel Rejection: Better than 5 dB.
Technical Manual Installation and Operation 8.5 SMX920 Model Number Configuration Guide The SMX920 build can be specified by the model number. The diagram below shows how the model number is derived from the wanted options. Consult RELM Wireless Corporation for availability details on specific configurations and options.
7100 Technology Drive West Melbourne, FL 32904 (800) 648-0947 Fax: (321) 984-0434 www.relm.com Ref.
