Associated British Ports agreed to field test the unit bytransmitting data from an existing tide gauge mounted in the Southampton container dock to the receiver at the VTS control centre some 6Km away. The test site was chosen as it was known to be noisy with existing radio equipment, there is no direct line of sight between stations, there is a large number of container ship movements in the area and many other working radio systems. Commenting on the two month test, ABP hydrographic surveyor,William Heaps said, ‘The spread spectrum radios are working flawlessly, the receiver is up high but the transmitter is still not in a good position, yet there are no problems so far!’ The radios use a spread spectrum technology to avoid interference and provide clear data communications between modems at baud rates up to 115.2 Kbps. The radio system is within the ISM frequencies (2.4-2.483 GHz) and makes use of a proprietary channel hopping technique to utilize up to eight channels within a 105 channel band. The technique was developed for military applications and is inherently immune from interference and jamming at ranges of up to 20Km. The radios can be set up in secure Master, Slave or Repeater modes providing various 'Point to Point' and 'Point to Multipoint'network combinations.