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Whip antennas for portable radios are often made of a series of interlocking telescoping metal tubes, so they can be retracted when not in use. Longer whips, made for mounting on vehicles and structures, are made of a flexible fiberglass rod around a wire core and can be up to 11 m (35 feet) long. The length of a whip antenna is determined by ...
The antenna may not be more than 20 feet (6.1 m) above the highest point of the structure it is mounted to, or the highest point of the antenna must not be more than 60 feet (18.3 m) above the ground (47 CFR 95.408(c)) if installed in a fixed location. [4] CB radios must include AM or SSB modulation and may include frequency modulation. [5]
Common types of monopole antenna are the whip, rubber ducky, umbrella, inverted-L and T-antenna, inverted-F, folded unipole antenna, mast radiator, and ground plane antennas. The monopole is usually used as a resonant antenna; the rod functions as an open resonator for radio waves, oscillating with standing waves of voltage and current along ...
After the 1973 oil crisis, the U.S. government imposed a nationwide 55 mph speed limit, and fuel shortages and rationing were widespread.Drivers (especially commercial truckers) used CB radios to locate service stations with better supplies of fuel, to notify other drivers of speed traps, and to organize blockades and convoys in a 1974 strike protesting the new speed limit and other trucking ...
The most common antennas are stainless steel wire or rod whips which protrude vertically from the vehicle. Physics defines the antenna length: length relates to frequency and cannot be arbitrarily lengthened or shortened (more likely) by the end user. The standard "quarter wave" antenna in the 25-50 MHz range can be over nine feet long.
Omnidirectional antennas are widely used for radio broadcasting antennas, [3] and in mobile devices that use radio such as cell phones, FM radios, walkie-talkies, wireless computer networks, cordless phones, GPS, as well as for base stations that communicate with mobile radios, such as police and taxi dispatchers and aircraft communications.
The AN/PRC-152 radio began production in 2005. [4] Since then, over 100,000 have been provided to the US military. [5] The PRC-152 has been notably used by Prince Harry during his service with the British Army, then a 23-year-old second lieutenant in the Household Cavalry.
For instance, if a radio wave passing a given location has a flux of 1 pW / m 2 (10 −12 Watts per square meter) and an antenna has an effective area of 12 m 2, then the antenna would deliver 12 pW of RF power to the receiver (30 microvolts RMS at 75 ohms). Since the receiving antenna is not equally sensitive to signals received from all ...
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