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RELM SMX920, Technical Manual

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SMX920 Base Station & Repeater 

Technical Manual 

 

RELM/

 BK RADIO

 

30 

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 .  

7.1.12 Mute Threshold Setting 

Test Equipment: 

 

♦

 

PC with Terminal software 

♦

 

RF Communications test set 

♦

 

+13.8VDC power supply 

SMX920 Testing – Rx Mute: 

1.

 

Monitor the low level muted RX VF (pin1 of RJ45) with RF Communications test 
set. Inject the correct RF frequency into the receiver for the test channel Set the 
test set to measure SINAD and reduce the RF generator until 8db SINAD is 
reached. 

2.

 

Adjust the front panel potentiometer (Mute control) so that the RX just goes into 
the muted condition. 

Further information on setting mute (squelch) can be found in Section 1.1.1

 

Summary of Contents for SMX920

Page 1: ...Base Station and Repeater Technical Manual SMX920 ...

Page 2: ......

Page 3: ...ectra Engineering Pty Ltd or any director officer agent or employee of Spectra Engineering Pty Ltd cannot be held liable for any loss or damage whatsoever arising in any way or any representation act or omission whether express or implied including responsibility to any person by reason of negligence Copyright Spectra Engineering Pty Ltd 1997 2003 Copyright RELM Wireless Corporation 2005 This work...

Page 4: ...SMX920 Base Station Repeater Technical Manual Revision 08 05 ii This page left blank intentionally ...

Page 5: ...rded 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 1 Changes to Figure 1 1 34 ...

Page 6: ...ronment constitutes a definite safety hazard DO NOT ATTEMPT INTERNAL SERVICE WHILE TRANSMITTING Thermal or RF burns may result from touching certain components within the power amplifier module while transmitting or operating the transmitter DO NOT SUBSTITUTE PARTS OR MODIFY THE EQUIPMENT Because of the danger of introducing additional hazards do not install substitute or lower voltage parts to th...

Page 7: ...1 3 3 Local Speaker Mic Socket and Front Panel Mute Squelch Controls 11 3 3 1 Description 11 3 4 Local Channel Change 11 3 4 1 Description 11 4 Options 13 4 1 Simplex Changeover Relay 13 4 1 1 Description 13 4 1 2 Installation 13 5 Technical Description 15 5 1 Exciter Section 15 5 2 Receiver Section 15 5 2 1 General Radio Management 16 5 2 2 TX Signal Processing 17 5 2 3 RX Signal Processing 17 5 ...

Page 8: ...bration 27 7 1 7 Temperature Calibration 27 7 1 8 TX Power Adjustment 28 7 1 9 Peak Deviation and Modulation Balance Alignment 28 7 1 10 TX Centre Frequency Alignment 29 7 1 11 Microphone Line Input Level Nominal Deviation Or Peak Deviation Mode 29 7 1 12 Mute Threshold Setting 30 8 Appendices 31 8 1 SMX920 Interface Connections 31 8 1 1 CN6 Simplex Relay 32 8 1 2 CN7 TX Output 32 8 2 SMX920 Test ...

Page 9: ...16 Table 7 1 Peak Deviation Settings 28 Table 7 2 Nominal Deviation 30 Table 8 1 SMX920 Interface Connectors 31 Table 8 2 SMX920 Accessory Socket Pinout 31 Table 8 3 SMX920 Test Points 32 Table 8 4 Rs232 Pin configuration 33 Table 8 5 General Specifications 36 Table 8 6 Transmit Specifications 37 Table 8 7 Receive Specifications 38 Table 8 8 Ancilary Specifications 38 Table 8 9 SMX920 frequencies ...

Page 10: ...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 29 Figure 7 3 Correctly Aligned Waveform 29 Figure 8 1 RJ45 socket viewed from front of SMX920 31 Figure 8 2 Front veiw of DB9 female connector and RJ45 Modular male connector 34 Figure 8 3 RS232 Cable 34 ...

Page 11: ...rovide a product that offers an extreme degree of flexibility for the installer and service person For example all options may be easily field retrofitted at a later date A common chassis is used for both vertical and horizontal version models Batteries may be installed at two or both locations in the chassis Internal wiring has been simplified and cut by 90 In addition servicing is simplified wit...

Page 12: ...esk or like An optional 19 3RU rack kit allows the standard horizontal version to sit on rack mounted tray The depth of the unit is 330 mm and the weight is less than 9 kg without the power supply duplexer or battery fitted With the addition of the Wall mount kit the vertical SMX920 can be mounted against a wall for convenience The unit consists of two main sub assemblies the main RF assembly and ...

Page 13: ...make this cable Loudspeaker and Volume Control A 3 Watt loudspeaker is provided to monitor on air received audio The volume is adjusted in the usual manner by Rotating the volume control clockwise to adjust the volume control for a comfortable listening level If no sound is heard temporarily un mute the radio by briefly rotating the Squelch Control full anti clockwise You can adjust the volume by ...

Page 14: ...lch sensitivity as described above to block out unintentional weak signals Front panel Channel Change Control Refer to Section 2 2 1 3 for channel select method Table 1 1 below explains the functions of the front panel LED s Each LED indicates the status of the SMX920 in real time As the LEDs are also software programmable it is also best to check the settings in software LED COLOR FUNCTION POWER ...

Page 15: ...so mounted in place of the Power Supply Module Hence a degree of power supply solutions can easily be accommodated for special applications like a portable Repeater Wiring for these special cases must be performed by the appropriate qualified personal Please contact your Dealer or Distributor should you require the appropriate assistance Conn Type Function Description Flying Lead DC Power input 13...

Page 16: ...ator frequency can be adjusted manually or electronically adjusted via software settings The fractional N synthesiser provides ultra low spurii while still maintaining fast lock times The frequency step size is auto determined at 5 0 kHz or 6 25 kHz The receiver section accepts the low level RF input signal and amplifies filters and conditions the signal prior to detecting the wanted audio compone...

Page 17: ... power levels are correctly set for each channel 1 2 2 Power Amplifier Module The PA receives the low level modulated RF signal from the Exciter RF output and amplifies and filters it to final output power level Forward and reflected power voltages are fed to the Micro Controller The PA is very compact and efficient for high reliability and low cost The heat sink has minimal temperature rise even ...

Page 18: ...to 9A band dependent for 50 Watts on transmit and the gauge of the DC cable fitted to the 12V supply connector should be adequate to ensure less than 0 5V volt drop at this current 2 2 Operation The SMX920 can operate in local control Base Station mode or Repeater mode via the front panel controls Setting up the SMX920 to operate in the wanted settings is straightforward and involves one main step...

Page 19: ... may point to another channel number in the channel list thus effectively providing 100 channels from the front panel channel selector 2 Front panel Push wheel switches The channel select port is internally wired to the Push wheel switches the desired channel is simply dialled up on the switches The 99 100 channels are selectable on the front panel This channel selector has the added advantage of ...

Page 20: ...tures will also depend upon the firmware version installed 2 2 2 Adjustments The SMX920 has adjustable parameters which are under the control of the Micro Controller These comprise of TX power TX VCO deviation TX reference oscillator deviation and TX reference oscillator frequency All of these are adjusted with the aid of the built in radio configuration menu system and all except TX power should ...

Page 21: ...nd any valid CTCSS tone to be decoded Any standard TX CTCSS tone may be associated with the programmed decode tone through the channel edit screen in the radio configuration menu system Multiple CTCSS tones are programmable for any channel providing Community Repeater functionality The DCS encoding function provides continuous repetitive digital word modulation to the transmitter The decode functi...

Page 22: ...l 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 The SMX920 will periodically update the terminal screen with the selected channel the power supply voltage and various other diagnostic information 3 Change the channel on the local channel switches and check that the channel selected ...

Page 23: ...he relay option is fitted the channels are programmed as simplex channels through the Channel Edit screen of the built in radio configuration menu system When the simplex mode is selected a small time delay is added to the transmitter RF to allow the relay to changeover and set the simplex operating mode respectively 4 1 2 Installation Components Required 1 Coaxial Relay Assy complete with Tx and ...

Page 24: ... a Communications Test Set to the SMX920 2 Monitor the Low Level muted RX VF Audio Pin1 of RJ45 3 Set the test set to measure Rx line level and ensure that the Receiver is operating correctly 4 Set the test set to measure Tx modulation level and Inject into RJ45 pin 4 with a audio generator output level of 10dBm 5 PTT the SMX920 RJ45 Pin 3 and measure the Tx Power and modulation depth Ensure that ...

Page 25: ...ts are the similar for the exciter and receiver sections The VCO consists of a common gate FET LC tank circuit The power supply to the VCO uses an 8 volt regulator and active filter for maximum noise rejection For standard modulation transmit audio is fed to the conventional point of the VCO varactor For 2 point modulation audio is also fed to the voltage control pin of the VC TXCO this in effect ...

Page 26: ...roller section accommodates an M30620FCAFP microprocessor IC2 a 16 kbyte EEPROM IC1 as well as I O latches and other miscellaneous circuitry The Micro Controller is responsible for ensuring that the radio acts as programmed by the user It stores the user entered parameters for each channel in EEPROM This information includes RX and TX RF frequencies RX and TX CTCSS frequencies as well as RF output...

Page 27: ... screen The SMX920 uses the technique of calibrating all Transmit Modulation level alignments in the Wide Band mode 25kHz channel spacing for maximum accuracy Gain setting resistor arrays switched under control by the microprocessor automatically scale the levels so as to set the correct modulation depth as required for Narrow Band channels 5 2 3 RX Signal Processing Raw Discriminator audio to the...

Page 28: ...oard Output latch IC4 drives the six LED indicators on the front panel The function is described in Section 1 1 1 An input port on IC2 serves to accept the programmed status of the 8 bit BCD channel select input from the front panel Pushwheel switches IC31 is a 3 Watt speaker amplifier which drives the internal speaker Microphone audio is into the front panel RJ45 connector In addition to RX VF Mo...

Page 29: ...on 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 ...

Page 30: ...he in built menu system check that the frequency tables and configuration settings are correct 6 1 1 Transmitter Section Connect the output of the Power Amplifier Module to a Comms test set or a RF power meter Using in built menu system select Diagnostics check the TXVCO locking voltage is between 2 14 V and there is no TXVCO Unlock alarm displayed If the locking voltage is out of spec or an Unloc...

Page 31: ... If the audio deviation is incorrect then go to the Transmitter alignment procedure If there is no audio modulation then check the audio level on pin 7 IC25B TP22 on the Microcontroller PCB If there is no audio on the above test point then go to section 6 2 else go to section 6 4 6 1 2 Receiver Section Using in built menu system selected Diagnostics check the RXVCO locking voltage is between 2 14 ...

Page 32: ...ith a CRO check the TCXO is oscillating on pin 12 of IC12 If all the above tests didn t pass then the VCO or IC9 may be faulty Return the to your Service Centre 6 3 2 RX Front End Solder a 2 way Berg header onto a flying coax lead Remove cut link I near the mixer M1 and then fit solder link J Inject a RF signal into CN5 Check the sensitivity is better than 105 dBm If the sensitivity is OK past thi...

Page 33: ...e TP4 is approx 7 8V and with a CRO check the TCXO is oscillating on pin 12 of IC14 If all the above tests didn t pass then the VCO or IC14 may be faulty Return the to your nearest Customer Service Centre 6 4 2 RF Power Using in built menu system increase the Transmit Power control to maximum and check that the output power is greater than 24 dBm To insure power control is at max Short C208 togeth...

Page 34: ...th a coax lead to a power meter Turn ON the supply voltage and the signal generator RF output PTT the PA and increase the generator output Don t exceed 24 dBm whilst measuring the output power output 50watts 25dBM If output power is low then turn the supply voltage OFF and lift one side of the capacitors connecting to the directional coupler and solder a flying lead to the lifted side Connect the ...

Page 35: ...Technical Manual Installation and Operation RELM BK RADIO 25 This page left blank intentionally ...

Page 36: ...e user intends to recalibrate and align the radio then steps 7 1 1 7 1 2 and 7 1 3 can be ignored as the model number serial number configuration and channel information will have already been loaded Using a PC or handheld serial computer running standard communications terminal software connect the device RS232 serial port to the RJ45 Accessory socket at the front panel of the SMX920 See section ...

Page 37: ...at automatically scales the deviation so the nominal deviation is not exceeded when a sub tone is transmitted 7 1 5 Power Calibration DO NOT USE THIS PROCEDURE TO SET THE TX OUTPUT POWER REFER 7 1 8 TX POWER ADJUSTMENT TO DO THIS Power calibration affects the forward and reflected power meters on the Diagnostics Screen This procedure requires a power meter and the relevant leads to connect the tra...

Page 38: ...gnment All Channels The peak deviation is aligned on wide band and without CTCSS DCS Tone enabled The following table specifies the peak deviation to align to Bandwidth CTCSS Option Peak Deviation Hz Wide 25kHz spacing NO 4800 Table 7 1 Peak Deviation Settings The alignment channel for this routine is the middle frequency band The test tones used in this routine are generated internally and are a ...

Page 39: ...e done on a per channel basis or all channels can be set at once Oscillator alignment is done using a digital potentiometer adjustment through the Built in menu system To carry out this procedure the transmitter output needs to be connected to a RF test set displaying the frequency error This procedure should be done after the deviation alignment procedure has been done Transmitter modulation we b...

Page 40: ...guration Menu Nominal Peak deviation 7 1 12 Mute Threshold Setting Test Equipment PC with Terminal software RF Communications test set 13 8VDC power supply SMX920 Testing Rx Mute 1 Monitor the low level muted RX VF pin1 of RJ45 with RF Communications test set Inject the correct RF frequency into the receiver for the test channel Set the test set to measure SINAD and reduce the RF generator until 8...

Page 41: ...icrophone Socket and RS232 Communication The socket provides a connection for a microphone Also provides RS 232 Communication between radio and PC See Table 8 2 Table 8 1 SMX920 Interface Connectors Pin No Function Comment 1 Low level muted RX VF Filtered and De emphasis 2 8V DC Current limited 3 Microphone PTT Pulled to 5V via 10k resistor Connect to ground for PTT 4 Microphone VF 600 ohms Z gain...

Page 42: ...PA Refl Volts 200mV 1V bad VSWR 6 P A Fwd Volts 0 5V Approx 2 8V 50Watts 7 5volt Supply 5V 5V Regulator Output 8 W B N B Control Line 5V OR 0V 5V Wide 0V Narrow Band Mode 9 Tx Drive Power control 0 12V 12V Maximum exciter RF power 10 RSSI Volts 0 5V 11 Rx Enable 5V Rx Enable 12 PA PTT 0V PA PTT Enable 13 Rx Lock Detect 5V RX PLL Is In Lock 14 Rx VCO Volts 2 14V Voltage Depends On Frequency 15 Rx S...

Page 43: ...25 Female connector with back shell 2 Metres of Flat phone cable or another RS232 complaint cable 8P8C RJ45 male modular connector 8P8C modular crimping tool 1 x Pair of side cutters Soldering iron and 60 40 solder Multimeter 13 8V DC power supply Fitting the 8P8C RJ45 Male Modular connector 1 Cut and strip Cable end to suit the 8P8C RJ45 male modular connector using modular crimping tool 2 Crimp ...

Page 44: ...tive Firmware Ver 0 2 0 and above Carriage return is required after typing RMENU The user will then be presented with a menu system from which various settings and configurations can be selected To exit the menu system the ESC key can be pressed Due to ongoing development please refer to www spectraeng com au for updates on firmware revision Getting started with Hyper Terminal 1 On the File menu c...

Page 45: ...S232 cable maybe induced onto the audio cable Figure 1 1 8P8C RJ45 Modular double adaptor 8 4 SMX920 Specifications Minimum performance to exceed the following for 30 MHz to 960 MHz AS4295 1995 ETS 300 086 Jan 1991 ETS 300 113 FCC Part 90 TIA EIA 603 BAPT 225 ZV 1 2098 German Soft keying CEPT T R 24 01 E Sept 1988 EC Marking EC EMC Directive 89 336 EEC RFS25 RFS26 RFS32 Conforms but may not be app...

Page 46: ...to 60 C Individual Module Dimensions Main board W 260 L 227 H 35mm PA W 78 L 300 H 60mm Standard LED indicators Power TX RX Tone Alert Repeater Speaker output 3 Watt Frequency Range Coverage 148 520 MHz Synthesis Method Non mixing PLL Fractional N synthesiser Modulation Direct FM two point method 2 5 kHz narrow band 5 kHz wide band Channel Spacing 25 kHz or 12 5 kHz software selectable Synthesiser...

Page 47: ...esponse 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 Better than 42 dB narrow Band Spurii Better than 90 dBc RF Switching Bandwidth Exciter Full sub band RF Switching Bandwidth PA Full sub band Duty Cycle 100 for 50W RF output with thermally controlled fan RF Rise Ti...

Page 48: ...than 46 dB wide band Better than 42 dB narrow band Receiver Front End BW Equal to band allocation Audio Bandwidth VF output 300 Hz to 3000 Hz 1 3 dB Receiver Audio Power 3 Watts nominal 5 Watts peak Squelch Opening Time Less than 20mS 20dB SINAD Squelch Closing Time Less than 100mS Conducted Spurious Less than 57dBm Table 8 7 Receive Specifications 8 4 5 Ancillaries Parameter Specification TX Time...

Page 49: ...ow shows how the model number is derived from the wanted options Consult RELM Wireless Corporation for availability details on specific configurations and options Band Frequency D3 148 174 MHz L3 350 385 MHz N2 400 435 MHz O2 425 460 MHz P2 450 485 MHz Q 485 520 MHz Table 8 9 SMX920 frequencies bands SMX920 Configuration R Repeater B Base Tx RX Freq Band Refer to Table 8 9 ...

Page 50: ......

Page 51: ...7100 Technology Drive West Melbourne FL 32904 800 648 0947 Fax 321 984 0434 www relm com Ref 0300 30973 700 08 05 ...

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