December 06, 2002
Tactical Radio Communications, installment 7
Penetration and blocking of radio waves
Radio waves are attenuated by almost all objects they pass through, e.g. air, people, trees, buildings and the ground. Dense objects such as earth or metals block radio waves very well. Only a few feet of either can make radio communications impossible. However, radio waves also bounce off objects, and this effect can be used to allow communications around corners and inside otherwise impenetrable objects such as steel buildings. Higher frequencies tend to bounce and penetrate more, thus UHF radios are the most suited for work inside buildings and cities. There is a practical limit to this however, and beyond 400-500 MHz the penetration of radio waves starts to fall off again.
Sensitivity
Good receiver sensitivity is an excellent way to make up for low transmit power. Increasing transmitter power takes more energy, and thus translates into shorter battery life on portable radios. Increasing receiver sensitivity usually does not require more power, so this is a desirable characteristic. Most modern radios have excellent sensitivity. Sensitivity is usually measured in microvolts, also abbreviated as uV. The lower the number, the better the sensitivity. A good radio will have a sensitivity of 0.2uV or lower. Up to 0.4uV is acceptable for UHF radios.
Posted by Eric Cartman at December 6, 2002 11:58 AM | TrackBack