All about RADIO
What is Radio?
Radio is quite simply any system that operates using the transmission and reception of radio frequency energy through free space.
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The Oxford English Dictionary definition of Radio is:
Radio. [mass noun] the transmission and reception of electromagnetic energy of radio frequency, especially those carrying sound messages.
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These days the RF spectrum is becoming increasingly crowded as growing numbers of devices are using ever more frequencies. Many devices use more than one band for communication and as more enter circulation the use of digital modes, encapsulated protocols and digital multiplexing is expanding rapidly. it is becoming increasingly common for 'sound messages' to be transmitted as packets of digital data rather than actual audio.
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Modern Developments.
There are many DV digital voice modes already in use that convert the analogue audio to and from digitally encoded stream of data which is transmitted of the air. There are many modern SDR (Software Defined Radio) systems that use computer software to control physical radio transceiver hardware, most SDR hardware consists of a box with no controls on it that plugs into a computer, all the 'controls and functions' are operated using software that runs on the computer. There is a wide range of SDR software available with continual development and new applications being released at an ever increasing pace.
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- Remote operation of Radio Equipment.
There are several manufacturers of radio equipment that now also provide SDR style software that lets the owner use their equipment from a remote location through an Internet connection using VOIP (Voice Over Internet Protocol) and Data communications between the remote control application and the physical hardware radio at their home location.
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Almost everyone will have listened to a broadcast radio station at some time or other.
It is relatively easy to understand the basics of how a radio broadcast system works.
A microphone and recording systems at the broadcast station are used as audio sources allowing the radio presenter to speak and play back pre-recorded program content at the studio.
In the studio the program audio they wish to transmit is fed into equipment that turns the program audio feed from the studio into a radio frequency signal suitable for transmission. This radio frequency signal is them amplified and transmitted from the broadcast station using a powerful radio transmitter connected to a large antenna designed to efficiently spread the broadcast radio signal out over the area that the broadcast station is intended to cover.
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The transmitted broadcast radio signal is then received at the listeners location by tuning in their radio receiver or shortwave set to the radio frequency of the broadcast station they wish to listen to.
The signal is received and the audio component of the received signal is amplified in their receiver then fed to a speaker, headphones or earpiece enabling them to hear the speech and or music program being broadcast from the radio station.
This is only one of a great many uses of radio technology but it is reasonably easy to understand the basics of how it works. Of course the above description is very simplified, there are actually many stages of mixing, filtering, monitoring, matching and adjustment that have not been mentioned and lots of other gubbins in the chain between the studio and the transmitter that go into making a broadcast station actually work properly.
There are many other uses for radio. Some are obvious and relatively easy to understand, others are not quite so obvious or straightforward and some are fiendishly complicated systems but they all have one thing in common, they rely on transmission and reception of radio frequency energy through free space.
There is a vast range of devices and equipment in general daily use that are often not thought of as radio when in actual fact they operate using a diverse range of radio communications technologies to send and receive information without wired connections. such as mobile telephones, GPS navigation systems, laptops, tablets, watches, tyre pressure sensors, alarm systems, process monitoring, control systems etc. There are even bicycle gear changing systems that use a very low power radio link instead of the typical mechanical gear cable arrangements that are familiar to most bicycle owners.
Radio is everywhere.
With an ever expanding range of systems and devices using a diverse range of radio technologies modes and methods to communicate, radio signals are everywhere and the electromagnetic spectrum is a very busy place.
The 'electromagnetic spectrum' covers a vast range of frequencies spanning from just above DC (Direct Current 0 Hz) with wavelengths of thousands of miles, to Gamma Radiation.
Gamma rays typically have frequencies above 10 exahertz (over 1 quintillion cycles per second!) Gamma Radiation has sub-atomic wavelengths of less than 10 pico-meters. (less than the diameter of a single atom).
The generally accepted 'radio spectrum' is from approximately 3Hz (wavelength 100Km/62miles) to over 300GHz. (wavelength 1mm/0.039inches)
The RSGB (Radio Society of Great Britain) provides a complete UK band-plan with official allocation information for frequencies from 136 kHz to 134 GHz.
There are also many devices used by astronomers and scientific researchers that operate well beyond the bounds of the accepted Radio Spectrum.
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Different types of equipment operate using a wide variety of different analogue and digital modes and modulation methods on various bands and frequencies depending on the required communication range and environmental aspects of the location for a specific service.
Things like WiFi and bluetooth devices are designed to operate over short range and use very low power levels. Commercial broadcast stations are designed to transmit over much longer distances, these obviously use higher power levels to achieve their design objective and provide wide coverage areas for their listeners. The power levels and frequency allocations are tightly regulated to ensure correct operation of each service while reducing interference to other radio users and services.
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The use of the radio spectrum is monitored, regulated and controlled by various official bodies around the World. Here in the UK use of the radio spectrum and associated licensing is looked after by OFCOM
You can browse through the Ofcom Spectrum Map online to see the diverse range of radio services and the frequencies they have allocated for their particular use.
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Is radio really that complicated?
Is radio really that complicated?
Radio sounds reasonably simple but it can be an incredibly complex subject. Many very clever people have spent their entire lifetime researching, developing and improving radio communications devices and expanding the usable radio spectrum.
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All radio signals travel as part of an oscillating electromagnetic field that passes through the air and the vacuum of space. The way these radiated fields travel can be described as waves. Different frequencies of oscillating electromagnetic 'radio waves' interact with different liquids, solids and semi-solid materials in various ways. These complex interactions range from total reflection to total absorption while some materials have properties that allow certain frequencies to propagate through the material while others are reflected or absorbed.
There are also vast amounts of RF communications signals that are propagated along wires such as; ADSL Modem Data on telephone lines, Coaxial cables carrying multiplexed channels of cable TV/radio broadcasts and programme information. And don't forget the many millions of miles of cables across land and under the seas that connect cities, countries and continents across the Globe! - Indeed RF communications are pretty much everywhere!
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Radio is everywhere! But not all of it is good.
Most households contain electrical or electronic devices that broadcast electromagnetic waves at frequencies from a few Hertz to over 5Ghz without people realising. Almost all electronic devices create some level of electromagnetic interference during normal use. No one tends to notice until these spurious signals interfere with the operation of other devices. (this type of interference from man-made devices is also known as QRM)
Radio interference, more common than You think.
As an example lets look at the 2.4GHz ISM band used by many wireless devices.
With the increasing use of 'WiFi enabled' devices in modern society and the wide acceptance and use of many other devices that 'share' the same 2.4 GHz ISM Band, things can get a bit busy up there.
Spectrum analysis of the ISM band can look pretty grim in a city or large town with heavy WLAN network traffic, Bluetooth, Video Devices, Cordless Phones, Tablets, ZigBee, Car Alarms, In Car Entertainment systems, Skype Phones, Devices with both WiFi and Bluetooth both in use and growing numbers of other devices that operate outside the 2.4GHz ISM band but also generate harmonics that create electromagnetic noise at frequencies within the ISM band.
Just think how many devices You have that are 'WiFi enabled'. When You get a lot of people close together with WiFi devices, the 2.4Ghz ISM band can be a very busy place with high levels of QRM seriously reducing network performance and reliability of connections between equipment.
OK. There is all this unwanted noise, Now what?
WiFi networking problems caused by QRM can often be reduced by selecting a different operating channel on the WiFi networking equipment. Many modern wireless network devices have the ability to automatically select the quietest or least busy channel based on what it can 'hear' on the channels available to it. If the interference impacts the network across all available channels, the next option is to change the location of the wireless access point, WiFi router unit and other wireless devices to reduce the interference to more acceptable levels.
Fixed Point-to-Point network links.
For fixed point-to-point network links, the use of directional antennas will reduce the reception of unwanted signals from other directions and increase signal gain in the desired direction. This helps to reduce the 'noise' from other devices nearby with a corresponding improvement in the signal you want, this can effectively extend the operable range of the link. One other positive effect of directional antennas is reduction of interference to other devices located around the systems on both ends of the link. This is a great improvement over omni-directional antennas, but is only useful between fixed points.
Access points, Hotspots and mobile devices.
Systems that provide WiFi connections for portable or mobile devices are generally known as an Access Point, 'AP' or a Hotspot. Most APs and Hotspots use omni-directional antennas which operate at relatively short ranges. (some also use multiple antennas in different orientations to improve short range coverage) There are many broadband routers and modems that have built in multi-band WiFi AP or Hotspot functionality that allows multiple devices to be connected simultaneously allowing them all to share one internet connection.
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There are also a great many WiFi Mesh networking devices commercially available that effectively provide the end user with a series of APs, Hotspots and other devices that can be easily set up and used to create a low powered network of devices that are spread out to increase the coverage area of Your LAN (Local Area Network) Some hardware units and even some software applications for existing portable and mobile devices can be used to create Ad-Hoc mesh networks between devices anywhere when required.
Beware of creating radio interference.
Beware of creating radio interference. You can be prosecuted for causing interference to other radio spectrum users and services.
It is worth noting that many low wattage compact fluorescent lamps and cheap imported LED lights are not EMC compliant and have been proven to cause some pretty serious interference across a wide range of radio frequencies.
The interference generated by non compliant luminaries, usually due to badly designed filtering in the power supply section of the devices to reduce manufacturing costs. The unwanted RF noise is propagated through the mains wiring in the building which then effectively broadcasts this noise causing a wide range of problems for many other electronic devices in the building or even in other buildings nearby.
Avoid using PLC (power line communications) devices as they work by pumping radio frequency energy through the mains wiring in Your home (or office) Mains wiring is designed to distribute AC power, oscillating at frequencies of 50Hz or 60Hz depending on your location. Mains power distribution wiring is NOT designed to carry Radio Frequencies and acts as a badly designed antenna system that can easily broadcast high levels of QRM. Using PLC devices can and very often does generate major interference across relatively wide areas.
If the noise from Your PLC devices is found to cause interference to important radio traffic including emergency services communications, aircraft navigation and other critical services communications frequencies it can lead to You being prosecuted.
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There was a case recently here in Scotland where interference was disrupting portions of the VHF bands causing loss of safety critical communication between aircraft approaching Prestwick and Glasgow City airports and air traffic controllers on the ground.
Radio spectrum monitoring vans with spectrum analysis and signal tracking equipment were deployed and the source of the interference was tracked down.
It turned out to be a domestic property that had fitted 'antique style' low energy lamps that used a type of LED filament that looked like old fashioned incandescent light bulbs. These were removed and the interference ceased. I do not know the fine details of the case and I probably do not want to know how much the investigation cost and who picked up the bill at the end of the day !
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East Ayrshire Radio Society
Ayrshire, Scotland.
© 2022 MM7WAB Hairy Paul