what is the radio spectrum?

radio waves

As if it were the Force in “Star Wars”, everything around us is energy, although not all of it can be seen or detected by the limited senses of human beings. The electromagnetic spectrum is the set of radiation waves emitted or absorbed by any substance, a field that can be measured and analyzed according to its frequency, wavelength or intensity.

Of the entire electromagnetic spectrum, the human being can only capture with his eyes the very narrow band corresponding to the visible light

Thus the radiation can be catalogued from that which has a shorter wavelength (gamma rays and X-rays) to ultraviolet radiation, visible light (a very narrow band within the total) or infrared, microwaves… reaching those of shorter wavelengths, electromagnetic waves and radio wavesthese are so necessary for communications and where some concepts such as FM (frequency modulation), DTT (digital terrestrial television) or 5G, which use different bands in this spectrum space, are already beginning to be heard.

Determinant in all of them is the wavelengthwhich would be the distance that one of these emissions travels when propagating through a medium during a cycle. Depending on the power at which it is emitted and the size of the wave (and the medium through which it is transmitted: air, water…) a certain distance will be reached. Some of these waves are even capable of passing through certain solid bodies, as is the case with X-rays (responsible for X-rays) or microwaves (so useful for defrosting and heating food).

In this last segment, that of radio waves the following bands are found, with their corresponding wavelengths expressed in meters and frequencies (wave repetition rate) expressed in Hertz:

-Ultra high frequency radio: 1 m, 300×106 Hz
-Very high radio frequency: 10 m, 30×106 Hz
-Shortwave radio: 180 m, 1.7×106 Hz
-Average radio wave: 650 m, 650×103 Hz
-Longwave radio: 10x103m, 30×103 Hz
-Very low radio frequency: 10x103m, 30×103 Hz

Within the radio frequency some correspond to sounds that can be perceived by the human ear while others are not (both in the high and low part of the spectrum) and by their classificatory denomination there will be some that are familiar for their use in radio station broadcasts in the AM and FM bands or also on television, the popular names they received in their early days the two public television channels in Spain: UHF and VHFrespectively ultra high frequency and very high frequency.

The proximity between the bands “occupied” by television broadcasts and mobile telecommunications (super high frequencies and extremely high frequencies, between 30 MHz and 300 GHz) makes it necessary to regulate them so that they do not interfere with each other. It is customary to reserve certain frequency ranges (bands) for certain wave emission technologies (from garage remotes to 5G mobiles) in order to avoid interference.

Given that the radio spectrum has finite limits and unalterable, and due to the public utility that its use represents, this band assignment is fixed by international standards and in some bands it is only possible to act by means of a governmental authorization. Thus, through the so-called administrative concessions, only those who have participated in the process regulated by the State may occupy a predetermined part of that band with:

-AM/FM radio stations

-Television stations in the bands reserved for DTT

-Mobile telephone operators

In the television field it has already been experienced the transition from analog to digital channels with DTT. In mobile telephony, from the times of the initial GSM, we have moved on to digital telephony, 3G, 4G and currently 5G.

Precisely because they are in adjacent bands in recent years sdTT channels have been retuned because some of the frequencies are “free” to be occupied by 5G telephony. And these transitions are not over yet, since as the 4G data connection is standardized and 3G connection becomes obsolete, the frequencies occupied by the latter band will become unused but may be reassigned to offer 5G connection, something that happens periodically with the auctions of some of these frequencies by the Government to which mobile operators compete.

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