SD-250 User Guide
Rev.
Rev. 0B Introduction The SD250 range is a 1 to 6 Watts RF data module at VHF and UHF frequencies. The SD250 is housed in a rugged cast-aluminum box sealed to IEC 529 (IP54) making it suitable for a wide range of mobile and fixed applications. All SD250 RF data module units meet the essential requirements of the relevant directives. In order to maintain this compliance the installation and safety information must be adhered to at all times.
Rev. 0B Preparing for use Unpacking and inspection Unpack the modem and check that you have received the following items: • SD250 RF data module • User Guide (this document) If any of these items are missing, please contact your supplier.
Rev. 0B Description of modem The SD250 is a network free, point to point RF data module that offers great flexibility in varied applications where wireless data or voice communication is needed. It can be used as a transparent radio, with no internal modem fitted, to allow users to facilitate the use of their own modem and protocol. The correct signal levels need to be used with the use of separate control lines, see the pin out table below.
Rev. 0B Features • Compact and rugged die cast box • Resistant to dirt, dust and water ingress (IP54 rated) • Network free, point to point communication • 1 / 6 watt programmable output power • Synthesized operation with 16 channel capability • SAT when used with Bell 202 / V.23 and FFSK modem or speech • Programmable 12.5 / 25kHz channel spacing • External modem / Direct FM • Internal modem options available: Bell 202 / V.
Rev. 0B External Connections 1. HD 9-way d-type (data, control signals and power supply) 2.
Rev. 0B 6 Mod. Input (Data) 1 Pin Outs Demod. Output (Data) Busy Detect Mic Input PTT / Prog. Data Output Prog. Data Input GND Speaker Output 5 9 B+ DB-9 PIN OUT table with input and output levels D-Type Pin No. 1 Function Description Data modulation IN (Tx Mod) Default : AC coupled signal directly injected Default : Analog signal to MOD through data low pass filter without 1KHz audio at 60% pre-emphasis.
Rev. 0B Program: Read 4 5 6 Ground B+ Busy (CD) Note: If the option modem board is installed, a resistor link can select RS-232 signal levels. See Modem manual Program : READ used for outputting programming data from mode Ground connection to chassis of the radio. Power supply input (Nominal 12V) Logic level output to indicate presence of a carrier.
Rev. 0B Operation Channel Selection Channels are selected by the use of internal switches and can be set as shown below. The top 4 screws will need to be removed to gain access to the switches, care must be taken to avoid any damage which could invalidate the warranty. The channel can also be changed by a serial command inputted from the external control system. CHANNEL NO.
Rev. 0B Transmit/Receive Operation The SD250 is put into transmit/receive either by using TTL levels, RS 232 levels or serial command, depending on the application and modem set up. When the radio is used with no internal modem, TTL levels (pin 3 on DB9) can be used. The default condition is active low for transmit, and active high, or not connected, for receive. It is possible to alter the polarity of this control signal by adding components, refer to the pin out table for details.
Rev. 0B Byte0 Start bit 1st 8-Bits (Command) Stop bit Byte1 Start bit 2nd 8-Bits (Data) Stop bit Byte2 Start bit 3rd 8-Bits (Check Sum) Stop bit Available Command and Data format Mode 1. 2. 3. Channel Change RTX Mode Selection Modem test mode 4.
Rev. 0B Status indicators The LED indicates the current status of the radio and if an external speaker is connected to pin 9 of the DB-9, audible tones can be heard under certain fault conditions.
Rev. 0B Programming The data modem is a pc programmable modem. The parameters available for programming include: • Frequency, channel spacing and sub-audible tones on a per channel basis • Standard radio settings such as power save mode, scan, tx lockout, tx timeout • Squelch enable • Modem options when the Bell 202 / V.23, FFSK, GMSK is fitted, such as data settings (flow control, block size etc) and timings.
Rev. 0B Installation Antennas It is important that any antennas are installed in a suitable location with an adequate ground plane. Ideally, multiple antennas should be separated by a minimum of a wavelength (at the lowest frequency), whilst still retaining a good ground plane for each antenna. Therefore, for a 400MHz system, the ideal separation should be a minimum of 0.75m, and for 150MHz system the minimum should be 2.5m.
Rev. 0B Cabling If possible, run RF cables separately from other cables and keep RF cables apart from one another to avoid interference / coupling. When fitting the modem into a fixed installation care must be taken in the routing of all cabling such that the insulation cannot become damaged. Fixing We recommend that the SD250 is securely fixed to a surface, either directly, or with a suitable bracket. The fixing hole center dimensions are as shown.
Rev. 0B Safety and general information Important information on safe and efficient use of your Radio device Exposure to radio frequency energy Your modem is a high power radio transceiver. When it is on, it receives and also sends out radio frequency (RF) signals. To help minimize human exposure to RF electromagnetic energy, keep transmission time to 50% or less.
Rev. 0B Vehicles with airbags Air bags inflate with great force. Do not place a radio in the area over an airbag or in the airbag deployment area, any radio may be propelled with great force and cause serious injury to the occupant of the vehicle. Potentially explosive atmospheres Turn off your modem prior to entering any area with a potentially explosive atmosphere, unless it is a radio type especially qualified for use in such areas. Do not remove install or charge batteries in such areas.
Rev. 0B Warranty and repairs The SD250 is a low maintenance device. Once installed it requires no ongoing maintenance. In the event that your SD250 RF data module needs repair, return your radio to an authorized Midland Radio supplier. Do not disassemble, modify or repair the unit unless the work is carried out by a Midland Radio approved supplier. Incorrect assembly, modification or repair may cause irreparable damage to your unit and will invalidate any warranty.
Rev. 0B Published by Midland Radio Corp. Any queries regarding information in this manual, please contact the Technical Services Group Leader at the above address. Information provided in this document is believed correct at time of printing but is subject to change without notice. Midland Radio will not accept liability for any loss, damage or costs howsoever caused as a result of the information provided.
