If you ask the modern man that can be heard on the radio , most probably, remember, at best, a few popular stations FM-band. Older people remember the "Mayak", working on medium and long waves. But in fact the airwaves "inhabited" extremely tight, a whole world, an invisible to the naked eye. " What they can see and hear on the radio, this article is about.
We begin a journey over the air from the bottom up, from longer to shorter waves.
SW-SW-HF ranges
Very low frequency (wavelength 10 km).
Radio waves so large wavelength of interest because not only are able to skirt the obstacles, but also penetrate into the water. At a frequency of 18,1 KHz work station, which is used to communicate with submarines. This station was constructed in Germany during the Second World War, then moved to Russia, collected again and works so far.
Naturally, the range of extra-long waves is not present in domestic receivers. However, signals at this frequency can be anyone, and absolutely free - the usual computer sound card is capable of recording signals of such frequencies. If you install the program on a laptop audio visualization, and connect to the microphone wire several meters long and rode away from the city and industrial noise - these signals is quite possible to see on the screen.
Long and medium wave (from 100 m to 10 km)
Display signals on a computer screen (Photo: Renato Romero, www.vlf.it)
At a frequency of 77 kHz you can hear the time signal transmitted by the station DFC77, located near Frankfurt. These signals clock and weather station can be automatically adjusted to the exact time. The shops can easily find a clock, with the function of such a configuration, but, unfortunately, most cities in Russia is not included in the area of reliable reception of these signals.
At a frequency of 198 kHz is still working the radio station " Mayak ". This station is on air since 1964, may well want to hear it on the long and medium wave and to this day.
At frequencies of 400-600 kHz beacons operate airports. With radiocompass aircraft can go exactly to the airport that is important in conditions of poor visibility. For example, in St. Petersburg at a frequency of 525 kHz, even at home receivers can hear the signal transmitted by Morse Code PL, referring apparently to Pulkovo.
Beacon at a frequency of 420 kHz, imaging signal (Photo: Dmitry Eliseev, personal archive)
The frequencies 2130 and 2150 kHz are used for communication on the railway, the negotiations drivers and dispatchers can be heard well at a distance of several kilometers from the railway on a standard consumer radios. Many may have seen a long wire with insulators, extended along the roof of the locomotive; this is the train station antenna.
Shortwave (10-100 m)
The information transmitted in a range of short waves, very diverse. This is a broadcast station, weather reports, meteokarty, etc. For example, station Hamburg Meteo clock transmits weather maps at the frequency 7880 kHz, to which is possible with the radio connected to the computer through your sound card. At a frequency of 10100 kHz, the same station broadcasts weather in teletype mode, which can be decoded, again, using the computer and software.
The frequency of 14 MHz is used by amateurs to experiment with different types of communication, among quite interesting can be noted for example, transfer images, this standard is called Slow-scan television (SSTV).
Meteofaks adopted by the author at a frequency of 7878 kHz (Photo: Dmitry Eliseev, Hamburg Meteo)
At the top of the HF-band (27-28 MHz) is a civilian, so-called "Sea-Bee» (Citizen Band) range. Anyone can buy a radio station operating in this range; such stations are widely used by drivers, travelers and etc.
Broadcast Bands
These ranges cover a large part of the ether. The lowest frequency is Channel 1 TV, working at a frequency of 50 MHz, the frequency of other channels are above and can cover frequencies up to 700 MHz.
In the broadcast a bit more confusion, as there is a "Soviet" VHF range, covering the frequency of 66-74 MHz and "foreign", which uses the frequency of 88-108 MHz. In different regions may be used either those or any other frequency, and not all home receivers can receive both ranges, so if you want to listen to the radio on FM / VHF is a need to consider when purchasing.
VHF
Range 117-137 MHz allocated to air communications. At these frequencies, dispatchers communicate with aircraft and employs automatic transmission system weather (Automatic Terminal Information Service, ATIS) and the coordinates (Aircraft Communications Addressing and Reporting System, ACARS). Of course, civilians can not use these frequencies for radio, but reception is quite possible - some consumer receivers, such as Grundig G6, have the support aviadiapazona.
Picture taken at short wavelengths (Photo: Paul Young, www.g0hwc.com)
In the range of 137 MHz transmit data meteorological satellites NOAA. Using the software, the calculation of the orbit, the radio and computer to get the photos from space with these satellites can be anyone.
Frequency 144-170 MHz used by public services - police, ambulance, fire, etc. In some regions, for these purposes are used as a frequency of 450 MHz and above.
Frequencies of 150 and 300 MHz are used for communication between the maritime, river vessels and shore stations.
At 433 MHz license-free radio stations operate standard LPD (Low Power Device). These devices can be used by all wishing to communicate over short distances, to observe the child with radionyani, as a beacon for finding pets, etc. At these frequencies may not work charms car alarms, buttons, opening gates, etc.
At frequencies of 900 and 950 MHz phone is standard GSM. Uses two spaced frequencies, which is why on a cellular phone can simultaneously talk and listen.
Radio waves have higher frequencies (1 GHz or higher) are distributed almost in line of sight. Therefore, they are used either for short distances (Bluetooth, Wi-Fi , DECT ), or with large directional antennas (satellite TV, data lines). At these frequencies are also transmitted signals from satellites GPS.
Image taken from meteorological satellites NOAA-17 (Photo: Frits Schouten, www.dt-space.co.uk)
At this very brief overview of radio coming to an end. The above list is, of course, not exhaustive, but if there is interest, anybody can deal with this issue alone, because the airwaves available to all without any restrictions. Moreover, this list and can not be completed, "point" then set early, because there are constantly new standards and technologies. For example, are already available Wi-Fi-routers, operating at 5 GHz, 10 years ago the use of such high frequency "at home" it would seem unrealistic. Wait and see ...
PS: In the end we would like to answer the question that will surely occur to some readers - how much radio, capable of receiving different types of signals? In fact, not very expensive.
Household receiver capable of receiving radio signals range 0.1-30, 76-108 and 117-137 MHz is about 5-6 thousand rubles that is quite comparable in price from affordable to every mobile phone. VHF radio, capable of working on the transfer of LPD-range and reception in the range 1-999 MHz, worth about 10 thousand. Expensive or not? According to the author, it is quite affordable if you wish money (many are spending far more on much more useless things), and whether to spare the money for something that helps to learn and discover something new?
The author hopes that a little opened for those interested in the world of radio equipment. Of course, the article this size can not cover everything, and the additional questions the author is always ready to respond to comments.
PPS: One more thing, which I would like to draw attention. In recent years, especially after the film "airwaves" has become a fashionable topic of the reception of radio signals from the other world. Many want to try to listen to the sound of the ether, scroll record this way and that, hoping to hear something that I want. Some even manage to catch something, but with proper fantasy and decrypt...
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