Radio Definition and 42 Discussions

Radio is the technology of signaling and communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device called a transmitter connected to an antenna which radiates the waves, and received by another antenna connected to a radio receiver. Radio is very widely used in modern technology, in radio communication, radar, radio navigation, remote control, remote sensing and other applications.
In radio communication, used in radio and television broadcasting, cell phones, two-way radios, wireless networking and satellite communication among numerous other uses, radio waves are used to carry information across space from a transmitter to a receiver, by modulating the radio signal (impressing an information signal on the radio wave by varying some aspect of the wave) in the transmitter. In radar, used to locate and track objects like aircraft, ships, spacecraft and missiles, a beam of radio waves emitted by a radar transmitter reflects off the target object, and the reflected waves reveal the object's location. In radio navigation systems such as GPS and VOR, a mobile receiver accepts radio signals from navigational radio beacons whose position is known, and by precisely measuring the arrival time of the radio waves the receiver can calculate its position on Earth. In wireless radio remote control devices like drones, garage door openers, and keyless entry systems, radio signals transmitted from a controller device control the actions of a remote device.
Applications of radio waves which do not involve transmitting the waves significant distances, such as RF heating used in industrial processes and microwave ovens, and medical uses such as diathermy and MRI machines, are not usually called radio. The noun radio is also used to mean a broadcast radio receiver.
Radio waves were first identified and studied by German physicist Heinrich Hertz in 1886. The first practical radio transmitters and receivers were developed around 1895–1896 by Italian Guglielmo Marconi, and radio began to be used commercially around 1900. To prevent interference between users, the emission of radio waves is regulated by law, coordinated by an international body called the International Telecommunications Union (ITU), which allocates frequency bands in the radio spectrum for different uses.

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  1. S

    Does Heinrich Hertz' apparatus include a proper antenna?

    How close to "antenna" was the metal barbell thing which was part of Heinrich Hertz' apparatus? Did he know in theory how to build a radio but just didn't have the right components to do it? I know someone around that time referred to the problem of radio in terms of needing proper sustained...
  2. S

    Minimum Frequency of FM Data / Catastrophic Error Scenario?

    Ever since I learned about FM something's been bugging me, which is that the PLL error correction acts on the encoded data, seeming to leave open the possibility of the shape of the data itself interfering with the PLL's interpretation of what the carrier frequency is. It seems dangerous to mix...
  3. H

    I Telescoping antenna -- why is there a knob on top?

    This is probably a trivial or even a stupid question, the reason I am writing here is I couldn't find something satisfactory online. I am a new amateur radio operator. Currently enjoying listening to SW and MW bands. I have a nice radio receiver with a long telescopic antenna. I have noticed...
  4. A

    Finding the resonant frequency of this "discriminator" demod circuit.

    This is the FM demodulation "discriminator" circuit. It is one of the simplest analog demod setups one could think of. An RF (FM) voltage signal is applied at V12 and the voltage at ' a' ' is supposed to contain the AF signal in its amplitude. The idea behind the circuit is that it resonates at...
  5. hagopbul

    Computer DIY ideas for quarantine time

    Hello all: I hope all are fine and well in their houses As I am looking into ways to fill my empty time other than reading undergraduate physics books I start to look around and wonder about giving online lessons for public school students , which they are now without a school , but I found...
  6. B

    Does Planck's relation apply to radio waves?

    I have some doubts about whether Planck's relation (E=hf) applies to radio waves. This has been bugging me because trying to apply Planck's relation to radio frequency results in some inconsistencies that I've been unable to resolve. BTW, I have no physics training, so please go easy on me...
  7. D

    I am trying to build a radio to transmit Morse code

    I am trying to build a radio to transmit morse code. I have built A wien bridge oscillator on a breadboard. I think the wien bridge Oscillator works. How long should The antenna be?
  8. Mark Palmer

    Electrical Crystal Radio question

    If anybody here has any experience with building a crystal radio, I would appreciate a response. My grandson and I are doing radio projects. This involves basic crystal build using a coil, diode, and resistor. The system is grounded and uses an antenna with no external power and a high...
  9. iVenky

    From Maxwell's equations to EM waves

    Hi, I just finished studying Maxwell's equations. Based on my understanding, when you solve maxwell's equation, you get the wave equation and it simplies to in a charge and current-free region. I understand that these two equations are similar to an equation of a wave in space. What I am...
  10. C

    Triangulation of Sound

    I would like to be able to triangulate a sound's location based on the inputs of two robotic sensors. I know this involves trigonometry, but I am a little out of practice. I think the practice of triangulation also is useful for radio signals. I would like to create a triangulation algorithm...
  11. B

    B Waves and Penetration

    Why do radio waves pass through walls while visible light can't? I guess this has something to do wit the wavelength. What I know is that higher wavelength means higher ability of penetration. So why radio waves penetrate obstacles?
  12. T

    How Do Microwave transmitters work without physical connections?

    So I recently picked up 40 of 10.525 GHz Microwave RADAR transmitters: I opened up one out of curiosity and had something like this (image attached) . I noticed some parts of the PCB aren't even connected to anything. How do the different shapes and sizes of the PCB interact with each-other...
  13. T

    Why does the sun affect radio wave propagation?

    I noticed HF radio waves travel farther and easier when the sun is out rather then during the night. Why?
  14. T

    Power Line powered FM radio

    I had an idea of building an FM receiver that is powered from the electromagnetic fields generated by power-lines. My question is , how can I make the electromagnetic field receiving antenna? Will a simple copper coil work? If so, can the same coil be used as the RF antenna or will that have to...
  15. T

    B Why does GPS require an accurate clock?

    Why do GPS need a cesium clock accurate to 10ns? Is this strictly for time keeping or is there some synchronization between satellites?
  16. T

    What makes a yagi antenna directional?

    How exactly do the elements "connect" to each other to make an antenna directional? I see some Yagi's have a reflector but most do not.
  17. T

    Electronics 3D Printed 2.25 Ghz Microwave RADAR horn antenna

    So I printed this antenna with some conductive filament , however the microwaves seems to be going between the layers of the plastic. I surrounded it with Aluminum and still leaking, what can I do to fix it? Can conductive silver paint work?
  18. T

    I What would be a useful application for 10 Thz nano-antennas?

    Reading: However I dont understand what a useful application for this is? can someone explain?
  19. T

    A ELI5 : Fourier Series

    Working on some microwave stuff, read about this but cant understand the explanations online.
  20. T

    Why do radio transmission harmonics occur?

    What I understand about harmonics, is when something is transmitted at high power, the antenna resonates on other frequencies besides the desired one. But Why?
  21. T

    B How do digital radios tune?

    I get how analog ones with knobs tune by physically changing length of elements to match the frequency, but what about the ones that just have a screen and you type in what frequency you want?
  22. OldWorldBlues

    Easy way to calculate losses for re-purposing a transformer?

    Hi everyone! This is my first thread :) I've been working a bit with AC and radio, and would like to make a simple(-ish) circuit in which a 1-volt peak audio signal is stepped up to around 5 volts with a transformer, and is fed into a crystal oscillator to make a crude-but-effective AM...
  23. C

    Trouble with getting AM reciever to work

    Hello, I have assembled the following AM radio reciever circuit: Purpose of the circuit: To recieve AM radio signals and provide the output audio of these signals ( demodulated ). Circuit elements: L ~ 1.5mH , C ~ 300pF , Amplifier IC: LM324N , Diode: 1N4004 ...
  24. T

    Propagation of radio waves

    Hello! I have been thinking of broadcasting a message into outer space. It sounds silly, I know, but that's just something I'd like to do for and with my niece. She's 8 years old and very interested in physics (as far as she understands it). I have some knowledge in electronics, I think I...
  25. ISamson

    Electronics DIY Radio

    Hello. I have been interested in radios lately and wanted to make one by myself. I know that it requires a lot of knowledge in physics and electronics, but what basics do I need to know? Frequency, antennas, voltages... Could there be any legal issues? I live in Australia. I am only a high...
  26. OldWorldBlues

    Basics of radio for a focused transmitter

    Hi there! I'm looking to create a small (max 20 foot range) radio transmitter, to direct a focused radio beam at a receiver, for the purpose of remote switching. Ideally, I would like the device to work at a relatively "exotic" frequency, as I would think there is a lot of radio noise where I...
  27. P

    According to Maxwell, a gamma ray can be as energetic as a radio wave (given equal E amplitudes)?

    According to the old thery of light the energy carried by by a wave is proportional to the amplitude of the electric field not to the frequency as planck proposed, so an eletromagnetic radiation in the gamma spectrum carry the same energy as a radio one if their amplitude is the same? They only...
  28. shihab-kol

    Doppler Effect In Radio Waves

    I have learned that the Doppler effect causes a change in wavelength (and thus frequency) in all types of waves Suppose there is a radio station transmitting waves of frequency 90 kHz and the antennae in my car is tuned to that frequency. Then I start to accelerate and thus I am changing my...
  29. Cool4Kat

    Book about the History of Electricity

    Hi there, My name is Kathy and I am writing a book about the history of electrical discoveries. I am writing the book for adults who have limited (or no) science backgrounds with a lot of personal details (like Bose who liked to give electric kisses to attractive women, or Alexander Bell's...
  30. R

    Q factor of an AM radio RLC circuit

    Homework Statement Suppose you want to use a series RLC circuit to tune in your favorite AM radio station which broadcasts at a frequency of 1.20 MHz. You would like to avoid the obnoxious easy listening station which broadcasts at 1.10 MHz, right next to the one you like. In order to achieve...
  31. F

    Wireless, RF, inverse fourth power law vs inverse square law

    When, in wireless communications, does the inverse fourth power-law become relevant? My understanding is that is that what cause the average signal power to degrade to the forth power is cancellation from self reflections. So by my way of thinking, an LOS point to point system, like a...
  32. Benoit

    Explaining Telecommunication

    How telecommunications work? I mean, there are so much waves around us nowadays, how my cellphone recognizes a single signal and rings only when it detects it? If my cellphone is a receipter, why can't I listen to my neighbor converstation, why isn't there a lot of interference and how waves...
  33. D

    New Year's Eve meeting

    I have a friend of mine which is an extraterrestrial. She travels in a ship around the Milky Way. She was likely in the Solar System, and she wants to attend tomorrow New Year's Eve at Plaza del Sol in Madrid, Spain. Her last communication was that she had faced a violent cosmic ray storm, and...
  34. onion3000

    Help with understanding modulation in AM, FM and PM radio

    I have a few questions about AM, FM and PM. 1. If FM (or PM) radio modifies the frequency of the signal, how is the signal picked up without having to change the frequency constantly? 2. If PM modulates phase, which modulates frequency, what is the difference between PM and FM? 3. Why is AM...
  35. Sam Gallagher

    Gift: SPICE Double Balanced Mixer Component

    << Mentor Note -- ZIP files are a security risk, and the file has been deleted. Please post the individual files instead. Thanks >> I saw a post from 2009 of someone who needed a mixer component to play with. So for learning purposes I zipped a symbol, schematic, and .sub file together for...
  36. synMehdi

    Antenna signal amplification

    I have an Antenna that receives signal coming from a wide band of distances, 10-2000 meters from a 10mW transmitter. I am working with 868 MHz band. What is the cheapest method ( or cheapest circuit ) to amplify this signal with an Automatic Gain Control LNA so that the received signal stays...
  37. S

    Do diamonds reflect EM waves ?

    Radio or any other wave in electromagnetic spectrum? Sound perhaps? And at what frequency(ies)
  38. G

    Biophoton Emission Outside Visible Range

    There are a lot of florescent proteins in the visible range, but why haven't we fount any above or below that range? I think a protein that emits radio waves could be very helpful both biologically and scientifically. Are we not looking for such proteins, or do they not exist?
  39. G

    Molecules With Radio Emission Under Current

    I am working on a project, however I am having trouble finding the right material for it to work. I am looking for a nano-material or any molecule that will emit a radio frequency when subjected to a voltage or a current at around 37 degrees Celsius. I would really appreciate it if someone could...
  40. J

    Is electrostatics the cause of radio waves?

    That is probably a badly worded question but I understand electrostatics and I want to send simple but efficient radio signals. If I switch on a strong charge in one place it'll effect a charge away from it depending on "Coulomb's law". How is this equation expanded to explain more efficient...
  41. Natanijel

    WiFi Signal Strength and Computer Orientation

    Hello everybody :) This is my first post! I have a mystery about radio communication that I was wondering about for a long time: If I have understood correctly, most computers have a single WiFi antenna in the shape of a rod, which is placed in a particular orientation. My question is this...
  42. E

    Is it possible to take a picture of the radio-waves on earth?

    I was wondering If anyone knows if this is possible, or why it might be a silly idea.