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The audio quality in the airband is limited by the RF bandwidth used. In the newer channel spacing scheme, the largest bandwidth of an airband channel is limited to 8.33 kHz, so the highest possible audio frequency is 4.166 kHz. [19] In the 25 kHz channel spacing scheme, an upper audio frequency of 12.5 kHz would be theoretically possible. [19]
Shortwave bands are frequency allocations for use within the shortwave radio spectrum (the upper medium frequency [MF] band and all of the high frequency [HF] band). Radio waves in these frequency ranges can be used for very long distance (transcontinental) communication because they can reflect off layers of charged particles in the ionosphere and return to Earth beyond the horizon, a ...
US frequency allocations chart, 2016. 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]
The following charts show the voluntary bandplans used by amateurs in ITU Region 1. Unlike the US, slots for the various transmission modes are not set by the amateur's license but most users do follow these guidelines.
The original allocation of channels consisted of only channels 1 to 28 with 50 kHz spacing between channels, and the second frequency for full-duplex operation 4.6 MHz higher. Improvements in radio technology later meant that the channel spacing could be reduced to 25 kHz with channels 60 to 88 interspersed between the original channels.
Ultra high frequency (UHF) is the ITU designation [1] [2] for radio frequencies in the range between 300 megahertz (MHz) and 3 gigahertz (GHz), also known as the decimetre band as the wavelengths range from one meter to one tenth of a meter (one decimeter).
For telecommunications, a frequency grid is a table of all the central frequencies (and corresponding wavelengths) of channels allowed in a communications system.. The most common frequency grid used for fiber-optic communication is that used for channel spacing in Dense Wavelength Division Multiplexing (DWDM) at wavelengths around 1550 nm and defined by ITU-T G.694.1. [1]
The aircraft emergency frequency (also known in the USA as Guard) is a frequency used on the aircraft band reserved for emergency communications for aircraft in distress.The frequencies are 121.5 MHz for civilian, also known as International Air Distress (IAD), International Aeronautical Emergency Frequency, [1] or VHF Guard, [1] and 243.0 MHz—the second harmonic of VHF guard—for military ...