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This requires either two separate radio channels or channel sharing methods such as time-division duplex (TDD) to carry the two directions of the conversation simultaneously on a single radio frequency. [2] The first two-way radio was an AM-only device introduced by the Galvin Manufacturing Corporation in 1940 for use by the police and military ...
The radio spectrum is the part of the electromagnetic spectrum with frequencies from 3 Hz to 3,000 GHz (3 THz ). Electromagnetic waves in this frequency range, called radio waves, are widely used in modern technology, particularly in telecommunication. To prevent interference between different users, the generation and transmission of radio ...
First air date. 1 January 1987. Links. Website. rfm.sapo.pt. RFM (from R enascença FM) is a Portuguese music radio station which belongs to r/com ( Rádio Renascença group). The station plays mainly contemporary pop music, especially national and international hits. The station opened in its current guise on 1 January 1987.
Radar beacon (short: racon) is – according to article 1.103 of the International Telecommunication Union's (ITU) ITU Radio Regulations (RR) [ 1] – defined as "A transmitter-receiver associated with a fixed navigational mark which, when triggered by a radar, automatically returns a distinctive signal which can appear on the display of the ...
Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another in vacuum, or into various parts of the atmosphere. [1]: 26‑1 As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. [2]
Frequency allocation. Frequency allocation (or spectrum allocation) is the part of spectrum management dealing with the designation and regulation of the electromagnetic spectrum into frequency bands, normally done by governments in most countries. [ 1] Because radio propagation does not stop at national boundaries, governments have sought to ...
Radio frequency. Radio frequency ( RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency [ 1] range from around 20 kHz to around 300 GHz. This is roughly between the upper limit of audio frequencies and the lower limit of infrared ...
Shortwave (HF radio) is used by transoceanic aircraft for communications with air-traffic control centers out of VHF radio range. Most countries with HF citizens'-band allocations use 40 or 80 channels between approximately 26.5 MHz and 27.9 MHz, in 10 kHz steps. Due to antenna-length requirements and the band's long-distance propagation ...