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FAQ's for Antennas
Q: I am a new user and my radio system is not working! What is wrong?A: Inspect your antenna, antenna cable and connectors for damage. Never operate a transmitter without an antenna connected as this will likely damage the transmitter.
RDT offer an assortment of directional and omni-directional antennas. While there are many factors to consider in making an antenna decision there are 3 inescapable truths:
1. Height is everything.
2. The radio will only perform as well as the antenna and cable connected to it.
3. Height is everything.
RDT 500mW data products have a range spec of 10 km with a unity gain dipole, using external directional antennas will improve performance. In general yagi antennas should be used for longer point to point links and omnis for shorter links or for repeater sites. However these are simply guidelines, if you need help with planning the antenna requirements for a particular installation please contact sales support
Q: Transmission ranges are quoted as 'line of sight'. What is 'line of sight'?
A: Line of sight is just that - if you stand by the antenna at one end of a link with a pair of binoculars or a telescope can you see the antenna at the other end? Line of sight means that there are no obstructions in the way. Keep in mind that with normal curvature of the earth you will be out of line of sight at 32 km if both end points are at sea level.
Q: How far can I get without line of sight?
A: It depends. It is very difficult to predict results in non line of sight conditions, but at 400-470 MHz the signal will penetrate buildings and trees quite well. Hills or solid metal objects will cause the most problems.
Q: What about lightning?
A: Of course a direct hit will destroy any electronic device but there is much that can be done to avoid damage due to the induced pulse from nearby hits. RDT supply surge arrestors and with an installed base of several thousand units (including many in high risk areas such as South Africa) we typically hear of one or two per year having been damaged.
Some customers turn to radio because there is a high risk of lightning. This is because a strike on a cabled SCADA system can be transmitted to every instrument. With a radio system there is no physical connection to spread the damage.
