ZRT Radio Modem Series

The ZRT is a high specification, low cost data radio modem which is ideal for stand alone wireless data applications or for integration into OEM products. A discrete component RF stage is used to give better performance than would be possible using the simpler "single chip" solutions found in many other low cost designs.

VHF (138MHz - 225MHz), UHF (406MHz - 512MHz) and 869MHz (868MHz - 870MHz) versions of the ZRT are available for simplex or half-duplex operation.

Applications include security, command & control, data logging, metering, SCADA, radio telemetry, remote switching or any similar applications where serial data needs to be transmitted reliably by wireless means.

Through the use of advanced DSP technology, the ZRT data radio has been optimised for reliability and low current consumption, making it particularly suitable for operation on remote sites without mains power.

The ZRT radiomodem can be supplied with an RS232-only, a combined RS232/RS485/RS422 or a 5V TTL serial interface. In each case, the speed of this serial interface 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 and there is an internal buffer to cope with situations where the interface baud rate is higher than the selected over-air rate. For 150, 300, 600, 1200 & 2400bps, FSK/FFSK modulation is used with V.23, Bell202 and MPT1327 tone-sets all supported. At 4800bps GMSK is used, while at 9600bps the modulation is 4-level FSK (4FSK). If high speeds are not required, the modem can be programmed to a slower over-air rate to take advantage of the associated improvement in receiver threshold.

The ZRT is available in low power versions adjustable from 10mW to 750mW and higher power versions covering 50mW 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 channels throughout Europe while the ZRT470TR-1 and the higher power 5W versions meet the tougher European EN 300 113 requirements and the equivalent USA (FCC) and Canadian (IC) specifications.

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 RF and modem parameters of the ZRT are all PC programmable via the serial port.

The ZRT radio data modem can operate transparently without packetising the data and without adding any other overheads, thereby maximising data throughput rates. Data is simply transmitted 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.

Store and forward repeater operation is possible by programming a routing table into the ZRT radio at the master-station site. Routing is based on the protocol address within the message to be transmitted and the ZRT currently supports repeater operation with MODBUS prototcol and a number of other similar protocols where the address byte is in a known position within the message

The RS232 and TTL versions support full RTS, CTS, DSR, DTR & DCD handshaking, although it is also possible to use just the transmit data, receive data and ground lines without handshaking. The combined RS232/RS485/RS422 version has it's DSR line simply looped back from the DTL line and CTS looped back from RTS.

Products available in the ZRT data radio modem range;

Model	Frequencies	Tx Power	Relevant Specifications & Notes
ZRT169TR-1	169.4 - 169.8125MHz	10mW - 750mW	EN 300 220, European harmonised 169MHz band (social alarms, meter reading & asset tracking)
ZRT450TR-1	406 - 465MHz	10mW - 750mW	EN 300 220, MPT1329
ZRT869TR-1	868 - 870MHz	10mW - 750mW	EN 300 220 European harmonised licence-exempt band
ZRT470TR-1	406 - 465MHz	10mW - 750mW	EN 300 220, EN 300 113 Higher specification than ZRT450TR-1 Suitable for use in licensed applications
ZRT170TR-5	138 - 172MHz	50mW - 5Watt	EN 300 113
ZRT225TR-5	175 - 225MHz	50mW - 5Watt	EN 300 113
ZRT470TR-5	406 - 465MHz	50mW - 5Watt	EN 300 220, EN 300 113, MPT1329
ZRT870TR-5	850 - 900MHz	50mW - 4Watt	EN 300 113

Add suffix "/RS232 only" for RS232 only with full handshaking.
Add suffix "/RS485+232" for RS232/RS422/RS485 interface with looped back handshaking lines.
Add suffix "/TTL" for 5V TTL interface with full handshaking.

RF DataTech - European designers and manufacturers of radiomodem, data radio and specialist radio telemetry, paging and wireless data products