Shortwave radio

Detection of buried objects Communication with submarines, electrical power Telephone audio range Navigation, sonar Navigation, radio beacon AM, maritime radio Shortwave radio, citizen s band Television, FM, police, mobile Radar, television, navigation Radar, satellite Radar, space exploration... 

Teller contrived nevertheless to follow the progress of the test. He stationed himself at a seismograph in a basement room of the Berkeley geology building. Herbert York, acting director at Livermore, timed a shortwave radio to the frequency of the Mike shot telemetry. When the shot was fired he called Teller in Berkeley. The two physicists had calculated the time a seismic wave from a successful shot would require to travel under the Pacific basin to northern California— about fifteen minutes. Teller remembers ... 

The longer wavelengths including power line transmission frequencies, broadcast radio, and shortwave radio can produce a general heating of the body. The potential hazards are greatest for those working close to powerful radio transmitters. 

Low frequency, with longer wavelengths, includes power line transmission frequencies, broadcast radio, and shortwave radio. Each of these can produce general heating of the body. The health hazard from these radiations is very small, however, since it is unlikely that they would be found in intensities great enough to cause significant effect. An exception can be found very close to powerful radio transmitter aerials. 

Most essential facilities are dependent on effective communication after an earthquake. Hard line and ceU telephone may not be functional, and backup systems should be provided. Equipment racks used for communication equipment must be able to withstand the shaking. Radio frequencies should be checked for compatibility with outside entities that must be contacted. Shortwave radio and satellite telephones are possible backup systems. Large or multi-site facilities may also need to maintain internal communication, and the viability of the existing systems should be considered. 

Fig. 2.17 Most geological field parties take an overnight trip to Cape Evans or Cape Royds on Ross Island in order to practice driving snowmobiles, setting up their Scott tents, cooking a meal, and communicating with McMurdo Station on their shortwave field radio (This photo was taken at Cape Royds with Mt. Erebus in the background in 1992 by T.M. Mensing)...

The plasma frequency derived in Equation 24.60 also applies to electrons in the ionosphere. Radio waves below the plasma frequency (amplitude modulated [AM] and shortwave broadcast) are reflected back to earth by the ionosphere and can carry over long distances. Frequency modulated (FM) and TV frequencies ( 50 MHz) penetrate the ionosphere and reception is limited to line-of-sight distances. Spacecraft and direct broadcast... 

AM radio waves (540-1600 KHz) as well as shortwave broadcasts (up to 20 MHz) can be heard over great distances because their waves are reflected back to Earth by the ionosphere. However, TV (Channel 2 is 55 MHz) and FM broadcasts (88-108 MHz) are limited to line of sight between the transmitter and receiver. With this information, what limits can you place on the electron density of the ionosphere ... 

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