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VHF Circuits

  

 

Very high frequency (VHF) is the radio frequency range from 30 MHz to 300 MHz. Frequencies immediately below VHF are denoted High frequency (HF), and the next higher frequencies are known as Ultra high frequency (UHF). The frequency allocation is done by ITU. Common uses for VHF are FM radio broadcast, television broadcast, land mobile stations (emergency, business, and military), long range data communication with radio modems, Amateur Radio, marine communications, air traffic control communications and air navigation systems (e.g. VOR, DME & ILS).
 
It is considered that one of the most significant events in the history of broadcast television regulation was the creation of an artificial scarcity of VHF licenses. The FCC's decision to locate television service on the limited VHF band changed the ways of television service and network competition in the industry. The rationale of this policy was to create a situation of increased competition and viewer choice.
 
Television was added to the VHF band in 1941 on channels one through six. During the war freeze, channel one was removed and used only for war purposes. Later, in 1945, channels seven through thirteen were added.
Marine VHF radio is installed on all large ships and most seagoing small craft. It is used for a wide variety of purposes, including summoning rescue services and communicating with harbours, locks, bridges and marinas, and operates in the VHF frequency range, between 156 to 174 MHz.
 
Although it is widely used for collision avoidance, its use for this purpose is contentious and is strongly discouraged by some countries, including the UK. VOR, short for VHF omnidirectional radio range, is a type of radio navigation system for aircraft. A VOR ground station broadcasts a VHF radio composite signal including the station's identifier, voice (if equipped), and navigation signal. The identifier is morse code. The voice signal is usually station name, in-flight recorded advisories, or live flight service broadcasts.