Search
and Rescue Newsletter Search
and Rescue Newsletter
Antenna
ConsiderationsAll antennas are electrical conductors. The purpose of a receiving antenna is to receive a radio wave. The antenna converts the radio wave into electrical energy that is passed to the receiver and converted back to audio or other indications. Since our receiving antenna is usually located at a considerable distance from the transmitter site, the energy (signal strength) is measured in millivolts (thousandths of a volt). In most instances the signal strength is less than a few micro-volts (millionths of a volt).
Vertical Vs Horizontal Polarization - Television antennas and FM radio antennas are mounted horizontal to the earth. Antennas that are mounted in this manner are referred to as "horizontally polarized" antennas. The antennas used with our receiving equipment are "vertically polarized", and are erected vertically.
The two (2) distinct antenna types help to prevent radio communications from police and fire departments, for example, from interfering with television reception. Horizontal polarization for TV and FM antennas is standard in North America. Since most man-made noise is vertically polarized, horizontal polarization was chosen because it helps to reduce interference from vehicle ignitions, neon signs, electric motors, hospital equipment, and thousands of other sources that are used in every neighbourhood.
Radio Waves - Are invisible and travel at the speed of light, 186,000 miles per second. Radio waves are considered to be a form of radiant energy, similar to heat or light. As you should already know, radiant energy is effected by air, water, ground terrain, trees, and buildings. Radio waves can easily pass through wooden structures, but cement and metal structures can limit, reflect, or completely stop radio waves from reaching our receiving antennas.
Understanding how antennas work can make ELT / EPIRB homing easier, and perhaps improve reception under a variety of conditions we must face during both training and SAR Actual tasking.
Paul D Turner
