RTcom Radio Modems manual

User Manual RTcom-Universal, Global Max and Outback Radio Modems Copyright Radio-Tech Limited 1998-2000[...]

2 CONTENTS INTRODCUTION 3 Selecting the frequency of operation 5 R.F Path Surveys 5 INSTALLATION Power Supplies 6 Location 6 Antenna Feeders 7 Lightning Surge Protection 8 Antenna Installation 9 Antenna Options 10 GENERAL ARANGEMENT RTcom-Global and Universal 11 RTcom-Outback 12 RTcom-Max 12 CONNECTIONS Data and Power 13 CONFIGURATION Operating Mod[...]

3 INTRODUCTION The RTcom-range of radio modem is intended as a direct replacement for cables over short, medium and long distance, serial data links. They are suitable for part of point-to-point, master to slave or scanning telemetry links, where the modem is either used on its own our in conjunction with existing cables. The modems also operate tr[...]

4 In many countries it is quite legal to operate systems without need for operating licences. These countries include the United Kingdom, Australia, New Zealand, Korea, South Africa, Scandinavia and the majority of Europe. However, operation in these countries is normally subject to the equipment first being approved to a defined standard, such as [...]

5 Frequency of operation Often there is not a choice over operating frequency. In most countries frequency allocations are very limited, by way of example in Europe there is only 433-435MHz UHF or 868-870MHz SHF. While the UK and many others offer VHF, UHF and SHF allocations. However other frequencies may be used subject to local government licenc[...]

6 If there is doubt over the signal reaching the receiver a path survey should be conducted. The outback modem includes a test mode that places the modems transmitter into constant transmit mode. This permits the measurement of signal strength at the receiver. Normally our modems will work satisfactorily with a signal level below 1uV (-107dBm). INS[...]

7 For battery powered operation in cold and damp climates the only reliable way to achieve long term operation is to use double IP65/7 enclosures, with both the outer and inner enclosure fitted with silica gel desiccant sachets. Please be aware that solar heating and wind chill can take the modem beyond its designed operating temperature range. Fur[...]

8 Lightning Surge Protection: A direct lightning strike can never be totally protected against or predicted. Currents exceeding 10,000A can flow vaporising antenna, feeders, towers and other such structures. Lightning conductors will give a degree of protection to the building but not always to the electronic apparatus within. Generally the probabi[...]

9 Antenna Installation The type and location of the antenna used can have a profound effect on your overall system performance and its legality. In point to point links it is good practice to make efficient use of the radio spectrum by selecting an antenna that will project the R.F energy into the direction of desired operation and similarly at the[...]

10 Warning : The use of gain antenna in some countries is not permitted. Similarly where ERP (transmitted power limits) are imposed the actual transmitted power must not exceed the limit stated. This means that the transmitter output power, less any coaxial feeder losses, plus the antenna gain must not exceed the specified maximum ERP. Before insta[...]

11 Guide to your RTcom-Global & Max Modem Status LED's 12-24V dc supply RS422 & RS485 Interface RS232 interface Links to select 2-4 wire RS485 Mode Switch for Data Rate and data format Channel selection switch (Global Only, See Table) Mode Switch for RS232 / RS485 Modes Carrier Detect LED (Global only) Reset Button[...]

12 Guide to your RTcom-Outback Guide to your RTcom-Max (Please take care when opening cover) Optional Location for Battery Solar/12-24V dc supply RS422 & RS485 Interface RS232 interface Links to select 2-4 wire RS485 Configuration Mode Switch Radio Module mounted in cover Connections as per Global Modem[...]

13 CONNECTIONS Data connections should always be made using screened cable. This will insure maximum rejection of interference from outside sources. Always use a common ground point. The RTcom Global, Eurpoa, MAX and Outback modems support RS232, RS422 and RS485 communications, both 2 and 4-wire. The RS232 port should be used for short cable runs o[...]

14 Pin Number Designation WRT Modem Notes 1 DCD Optional not normally needed 2 RX (data) RS232 input data to modem 3 TX(data) RS232 output data from modem 4 RTS Optional not normally needed 5 GND Ground 6 B RX(-) RS485/RS422 7 A RX(+) " 8 +Vs Supply 7.5 to 15V dc 9 N/C 10 GND Ground 11 Z = TX(-) RS485/RS422 12 Y = TX(+) " 13 +Vs Optional [...]

15 On the Global and Max modems two dip switches are provided for the selection of the desired operating mode and two plug links are provided from the selection of 2 or 4 wire RS485 operation. A further DIP switch is provided on the Global modem for frequency Channel selection. Switch Number Function 1 Baud Rate (See Table) 2 Baud Rate (See Table) [...]

16 OPERATION The RTcom protocol permits 100% transparent operation and direct cable emulation. Simply what goes in comes out! R.F. packet framing, code balancing, encryption and preambles etc are taken care of automatically within the modem. Standard industrial communications protocols such as Modbus include a secure CRC 16 or 32 error check code o[...]

17 COMMISSIONING The data rate, parity and number of data bits are set using the dual in line switch located above. If a scanner is available the chosen channels and the adjacent channels should be scanned for activity. With frequency agile products such as the Max and Global a fee channel should be selected as far away as possible from the channel[...]

18 system. This results in the messages becoming fragmented, thus confusing the modem into thinking the end of file has been detected. The other common problem, in particular with WindowsTM Hyper Terminal, is the way in which is deals with errors. Should an error occur it attempts to re-establish the link from both ends simultaneously, something of[...]