SRT Radio Modem

SRT Radio Modem

  • Simplex or Half Duplex
  • Up to 9k6 bps over-air in 12.5kHz channel
  • Front panel channel switches
  • Internal modem with RS232 data interface
  • DIN rail mountable
  • Low power consumption
  • Programmable power-save modes
  • Forward Error Correction (FEC) selectable at 9k6 bps
  • Highly sensitive receiver
  • Supports “Store & Forward” operation
  • Easy configuration using supplied software

The SRT series of DIN rail mountable, ultra low current consumption data radio modems is designed for use in scanning telemetry radio systems, SCADA networks or in stand-alone radiotelemetry applications.

The SRT radio modems are simplex/semi-duplex radios for cost conscious VHF or UHF applications which require a very flexible product, but do not need the full duplex or optional external modem capabilies of the ART.

The SRT radiomodem has an RS232 serial interface whose speed can be set independently of the chosen over-air data rate. The over-air data rate can be set to a range of values between 150bps and 9600bps in a 12.5kHz channel and there is an internal buffer to cope with situations where the interface data rate is higher than the over-air rate. If high speeds are not required, the modem can be set to a slower over-air rate to take advantage of the associated improvement in receiver threshold.

An I2C bus connection is also provided, which can be used either as an additional serial port or for direct connection of selected I/O modules such as the ART710.

The SRT is available in a low power version adjustable from 10mW to 750mW and a higher power version covering 100mW to 5W. The desired transmitter power can be set accurately within the relevant range under software control. The low power versions meet the ETSI EN 300 220 specification for use in licence-exempt frequency allocations throughout Europe while the higher power 5W versions meet the tougher European EN 300 113 requirements. The 5W UHF (406MHz-465MHz) version also complies with the UK VNS2111 specification which supercedes the older UK-specific MPT1411 requirement for scanning telemetry systems.

The receiver is a very low current, double conversion superheterodyne with an active balanced mixer for very good intermodulation performance. Careful attention to spurious response, adjacent channel and blocking performance, makes the product ideal for crowded telemetry radio channels.

The SRT data radio modem can operate transparently without packetising the data and without adding any other overheads, thereby maximising data throughput rates. Data is simply sent and received with minimal delay. Alternatively, a simple packetisation option can be enabled for use with old or non tolerant protocols, where the presence of a mute (squelch) tail may cause a problem at the end of a message.

For more complex applications, the SRT supports Hayes “AT” command set, MODBUS and various “Store and Forward” repeater modes.

The RF and modem parameters of the SRT are not only PC programmable via the serial port, but can also be remotely configured, monitored and managed over the air.