December 03, 2002
Tactical Radio Communications, installment 4
Power
Transmitter power output is the amount of energy that is sent to the antenna. Power is measured in Watts, just like electrical appliances. However the antenna can affect how much of this power actually gets sent into the air. Some antennas absorb or reflect large amounts of power (up to 90% in some cases) back to the transmitter. Such poorly performing antennas are usually seen at lower frequencies when size of the antenna is more important than efficiency.
More power translates into longer communications distance. As a rule of thumb, signal strength decreases as a square of the distance from the transmitter. What this means in practical terms, is that if you can talk for 1 mile with 1 watt of power, to stretch that to 2 miles you will need (2 squared) 4 watts. To talk 3 miles (3 times the distance) you will need 3 squared or 9 watts.
Most portable radios transmit 0.1 watts (or 100 milliwatts) on low power and 1 to 5 watts on high power. Mobile radios typically transmit from 10 to 100 watts. Base station radios or radios with external amplifiers can transmit up to 1000 watts or more.
Posted by Eric Cartman at December 3, 2002 04:17 PM | TrackBack