Data Loggers
Powerful Data Logger and Flexible Data Acquisition and Data Logging Systems

1. To receive radio messages from other modems and relay them to the device connected to its serial port (the host computer at the local end, or the dataTaker at the remote end);

2. To receive information from the device connected to its serial port (computer or dataTaker) and relay this, via its radio transmitter, to other modems.

When purchased in pairs, the modems are shipped ready for point-to-point communication between a dataTaker and its host computer (Figure A). That is, both the computer-to-modem link and the modem-to-dataTaker link are preset to the dataTaker's default data rate. Future configuration changes (data rate or operation mode, for example) can be made quickly and easily using the FreeWave setup program, which is stored in each modem and accessed via a computer running any terminal software package (dataTaker's DeTerminal, for example).

Spread Spectrum Radio
FreeWave modems use "spread spectrum" radio signals in the 915?928MHz range (902?928MHz available by special order). Spread spectrum technology was originally developed in the 1940s as a secure anti-jamming, anti-interference communication method for military use, and is virtually immune to interference compared to traditional (narrow band) methods. Today, its excellent interference rejection - along with good transmission through glass, wood, plaster and other common obstacles -makes it most suitable for data transmission in adverse situations. Moreover, because of spread spectrum's lower transmitter power density, FreeWave modems are unlikely to interfere with other electronic equipment.

In addition, FreeWave's sophisticated communications protocol ensures an orderly, reliable, error-free flow of information over the radio link.

Modem Range
FreeWave modems have a range of 15 kilometers (line of sight) using the standard 75mm whip antenna provided with each unit.
If required, the range of a communications link can be extended by adding up to two additional FreeWave modems into the link. The extra modems are simply configured as repeaters, and each extends the range of the link by 15km.

External Antenna
An external omnidirectional antenna is available for installations where the standard "desktop" antenna provides insufficient range. Typically, the external antenna is mounted as high as possible (on a mast or rooftop, for example) and the 9-metre cable provided with the external antenna is run back to the modem's SMA connector.

Licensing Requirements
No license is required in Australia and the USA. Elsewhere, contact your local authority.

Power
FreeWave modems require a 10.5?18Vdc power supply. A mains adapter is provided with each modem, or an external battery can be used.

Indicators and Connectors
The modem front panel contains three indicators (Carrier Detect, Transmit and Clear to Send) and a recessed push button used for putting the modem into Setup mode. The rear panel contains the power socket, the RS232 connector, and the external antenna connector (SMA, left-hand thread). The standard whip antenna screws into the top of the case.