Radio Definition and 691 Threads

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.

View More On Wikipedia.org
  1. T

    Passive long range sensor using radio wave distortions?

    Greetings PFers, I was thinking about how it would be possible to "scan" something without having visual or physical contact (and without have a superconducting magnet, etc...) Lets have this device detect something conductive. If a device were to emit an electric field pulse of very...
  2. L

    Why Choose High Frequency Radio Waves for Long-Distance Communication?

    What is the advantage of high frequency radio waves over low frequency radio waves? E.g. Wi-Fi 2.4 GHz over FM radio ~100 MHz.
  3. M

    Extent of human radio broadcasts photo

    Let me remind you all how small we are :D not that most of you need to be told :P Credit for the photo belongs to Nick Risinger. Website credits in the bottom left hand side of the picture.
  4. B

    Radio waves to gamma particle question

    Hi all, so iv'e been looking around and can't find an answer to a question i have. I have read articles on wikipedia and understand the "basics", but i still cannot fully visualize the concept. Question: Do all frequencies on the em spectrum emit the same particles? i know that visible "light"...
  5. F

    Mechanism of heating organic matter by radio waves

    I'm doing a study that involves radio waves passing through organic matter and have come across several sources that state that radio waves may heat organic matter when passing through it (For example: http://www.mobilfunkstudien.org/downloads/peleg_wm_10.5923.j.biophysics.20120201.01.pdf)...
  6. F

    Efficiency of DSBFC Modulator vs. Balanced Modulator: A Comparison

    Homework Statement The figure shows a balanced modulator. Inputs to the top modulator are the information signal and the carrier signal and the inputs to the bottom modulator are the inverse of the information signal and the carrier signal. Then the output from the bottom modulator is...
  7. mishima

    Stargazing What Kind of Paint Is Used for Radio Telescopes?

    I was wondering what kind of paint is used for radio telescopes, generally. In the case of the Green Bank Telescope, the idea is to get white at visible wavelengths, black at mid-infrared, and transparent at radio wavelengths. Titanium dioxide based paint was one substance cited on the...
  8. B

    Radio waves vs material & shape

    What happens when radio waves of around 1900mhz (cell phone) is confined in an aluminum box. Will the waves be able to pass through the box to the outside. What would be the best way to get the waves to the outside of the box with only modifying the box. If i cut a hole would that improve how...
  9. R

    How Should the Parabolic Dish Be Aligned for Optimal Radio Wave Reception?

    Homework Statement Parabolic radio telescope. Dish is fixed and across its centre a cable is suspended carrying a beam on which equipment is mounted to pick up radio waves. Basically it's just a parabola on the cartesian plane. How would you adjust the parabola ( focus, directrix, vertex etc...
  10. N

    Why are the bass notes of a car radio heard by people on the street an

    Homework Statement Why are the bass notes of a car radio heard by people on the street and not the high notes The Attempt at a Solution I think it has something to do with fixed and free end boundaries and may have something do with the fact that the high notes are being reflected...
  11. J

    Radio: How does a demodulator work?

    Can someone explain how a demodulator or detector for a radio works in layman's terms? It is the part of the radio that separates the sound from the carrier wave. For both am and fm. I would like to know how it actually does this. Also, can someone explain how a coil in a circuit affects its...
  12. Saitama

    Relating Path Difference and Intensity in Radar Signals

    Homework Statement Homework Equations The Attempt at a Solution The path difference between the two rays being received by antenna is ##h/cos(\alpha)## but how to relate the path difference with the intensity?
  13. J

    FM radio system for simultaneous translation

    Maybe someone who knows about FM radio transmission equipment can help me. I'm the pastor of a 200 member church in Berlin Germany. I would like to build a small system to broadcast simultaneous translation. I would think all I need is an FM transmitter, microphone and FM radios or headset...
  14. R

    Building a ~20khz Radio on the Cheap

    I am trying to build a radio to receive a 200 hz - 20 kHz signal. Can anyone give me a starting point as to what specific parts I would need (breadboard, operational amplifier, transistors, resistors, antennae, etc..)? The signal frequency is the most important thing for this project. Thanks...
  15. N

    Can Radio Waves Change the Electric or Magnetic Properties of Metals or Liquids?

    So mobile devices use radio waves so I had this thought that if there was evidence linking radio waves with changing organic tissue structure is the evidence that radio waves can be used to change the electric or magnetic properties of metals or liquids? Underwater walk talky jabbering for...
  16. E

    Interference from two radio antennae - simplistic and workings include

    Is this correct ? I have an issue for the minima formula when n=1 I get theta = 90 degrees. This doesn't make any sense. Is my method correct ?
  17. P

    FM Radio receiver in RLC circuit with .200 microH Inductor

    Homework Statement The tuning circuit in an FM radio receiver is a series RLC circuit with a 0.200 µH inductor a. The receiver is tuned to a station at 104.3 MHz. What is the value of the capacitor int he tuning circuit? b. FM radio stations are assigned frequencies every 0.2 MHz, but two...
  18. M

    Intensity and frequency of radio waves

    Hi, I am not a physicists and have been trying to understand some basic concepts about electromagnetic waves in the context of telecommunications. Now, this is what I know so far: the energy of electromagnetic waves is proportional to it's frequency (E = h*f), and basically it's the energy...
  19. E

    Twin Source Interference - Radio Towers

    Homework Statement http://www.mediafire.com/view/?09c89b8986u5zls The above is a question from my problem sheet. I've got no idea how to attack this since its been very poorly explained in my lecture handouts. Can someone please help me ?
  20. R

    Finding resistance in an LC Circuit (FM Radio)

    Homework Statement The figure shows a simple FM antenna circuit in which L = 8.22 µH and C is variable (the capacitor can be tuned to receive a specific station). The radio signal from your favorite FM station produces a sinusoidal time-varying emf with an amplitude of 12.2 µV and a frequency...
  21. coktail

    FM radio waves and radio stations

    Hi there. I have a (hopefully) quick question here. FM radio stations transmit their information by manipulating the frequency of radio waves, but each radio station is assigned to a specific frequency. If the frequency broadcasted by a radio station is constantly changing (to transmit info)...
  22. M

    Radios, Radio Antennae, Reception, Transmission

    So couple questions. My assumption is that a radio antenna gets bombarded with all frequencies at the same time. So there has to be a discriminating circuit with a radio to act as a frequency filter. Well could I do this naively with a low pass filter and a high pass filter together? In...
  23. K

    Small radio telescope for hydrogen 21cm emission line

    Hi I am trying to figure out if there is call for a small, commercial, educational radio telescope to measure the 21cm emission line of hydrogen. We have been developing an instrument with the following characteristics: - The antenna would have a size of about 1m x 1m. Because the...
  24. O

    Finding the distance of a space shuttle using radio wave transmissions

    Homework Statement Mission control sends a brief wake-up call to astronauts in a far away spaceship. 2.4 seconds after the call is sent, Mission Control can hear the groans of the astronauts. How far away (at most) from Earth is the spaceship?Homework Equations Have yet to find a suitable...
  25. W

    Radio Signal Basics: Generating & Receiving

    What are the most basic components I need to generate and receive a radio signal and how would I arrange them? For instance imagine I want to make an LED in my bedroom flicker when my front door opens. Firstly how would I make this happen at the most basic level, so that some signal is...
  26. U

    Understanding the Path of Radio Waves (particularly 900 MHz & 2.4 GHz)

    I'm interested in how to understand exactly how radio waves will propagate in a particular situation. I know that they are absorbed by metal and water, pass through other materials albeit with loss of power, and reflect or bounce off of surfaces as well. How do I know whether a radio wave will...
  27. Spinnor

    Estimate of photons/electron/cycle for radio antenna?

    Should it be straightforward to estimate the number of radio wavelength photons emitted per electron per cycle (or is it number of electron cycles per photon) of a half wavelength radio antenna running at 100MHz and 1000 watts power output? Is it many photons per cycle per electron or is it many...
  28. D

    How do Radio Waves work when used for FM or AM Radio transmission?

    I would like to know about radio waves used for FM or AM radio. I have read many articles that say, "The sound is encoded and rides on a carrier radio wave". How is that encoded? I am under the assumption that waves just have a frequency and wavelength and that is all. If a wave is transmitted...
  29. B

    How do I get into Low Powered Radio?

    I want to know how to begin legally getting into LP Radio. I want to learn how to set up a system, get a license and all the works. Does anyone know where I should start? I already saw the FCC FM radio application and it is insanely huge, but if anyone can decipher what they are saying it could...
  30. F

    OpenFTA radio buttons invisible in defining Primary Event

    I am test driving an app (OpenFTA, http://www.openfta.com) for small Fault Tree Analyses on Windows 7 64-bit. In one of the functions (defining a "Primary Event"), the radio buttons are not visible. Googling with the following search phrase does not yield anything relevant: open-fta...
  31. N

    The future of Radio Astronomy (your thoughts)

    "The future of Radio Astronomy" (your thoughts) Hello all, I'm doing an extended project on "the future of radio astronomy". And I would like to know people's opinions on the "future of radio astronomy" and what advancements the field of radio astronomy is expected to make in the future...
  32. S

    Question about Heliopause / radio noise

    I'm writing a story that takes place at about 200 AU from Sol - it's outside the heliosheath, where solar wind and interstellar wind meet. We haven't managed to send any spacecraft that far out yet, though Voyager 1 and 2 will get almost that far before they run out of thruster fuel and...
  33. J

    Radio Transmission Power and Detection in Relation to Alien Communication

    I sometimes hear on astronomy documentaries that our earliest radio transmissions could be received by aliens in our galaxy. Assuming the stations power was 1000kw at 1 mile(wild guess on my part) the power of the signal at 1 light year would 1000kw/7 trillion squared. Is this right? If so...
  34. Chronos

    Exploring Transient Radio Signals: Could They Be ET?

    This paper 'Provocative radio transients and base rate bias: a Bayesian argument for conservatism', http://arxiv.org/abs/1211.7338, discusses transient radio signals as possible signs of extraterrestrial intelligence. I knew of the 'WOW' signal, but, was unaware of other similar detection events.
  35. JJBladester

    Stereo indicator light in FM radio

    Homework Statement How does the stereo light in an analog FM radio turn on when you tune into a stereo station? The Attempt at a Solution I know that radio tuners work on the concept of resonance. Current and voltage levels spike up at and near the resonant frequency of a circuit...
  36. M

    Cellular radio systems questions

    With regards to cellular radio systems1. how many bits of information does each cycle of a sinewave carry on a minimum channel? modulator characteristics 2. A system has narrowband fm characteristics.. name me a rule which is an approximate technique to find the necessary freqeuncy deviation...
  37. J

    What is different in Solar Radio vs Radio Flux 10.7 cm?

    Referring to following links, I would like to know whether Solar Radio is equal to Radio Flux or not, it seems that it describes Solar Radio in different format. Are they monitoring the same objects? Does anyone have any suggestions on what the different is between them? Thanks in...
  38. N

    What is the purpose of heterodyning in radio astronomy?

    Hello all, I'm aware that heterodyning is a radio signal processing technique as kindly explained by the Wiki article on the topic (http://en.wikipedia.org/wiki/Heterodyne). However I don't understand how radio astronomers use this technique to aid their observations, what sort of...
  39. J

    What is the Nature of Solar Radio Flux?

    Referring to following link about Solar Radio Flux, I would like to know more about Solar Radio Flux, is Solar Radio Flux different from Electric Flux? What is the major difference in term of properties of their fluxs? Does anyone have any suggested materials on what Solar Radio Flux is about...
  40. J

    So if FM radio signals modulate the frequency of the EM wave

    then how can you tune into, say, 101.1 when its not at 101.1 MHz all the time given the frequency change?
  41. Square1

    Automotive Car battery life - playing radio

    How long have you ran your car battery running on "lowest key position", just playing the radio. How long do you think a 05 model should have it's battery last for this. Range? :]
  42. Drakkith

    Stargazing How do radio telescopes form images?

    Alright, I know about optical telescopes, but I haven't a clue how a radio telescope forms an image. I'm used to pixels on CCD's measuring photon counts, but how are the radio waves detected and an image created from them?
  43. L

    Homework question about radio waves

    "At what minimal height must be situated the point of reflection of a radio wave emitted in Montreal and received in Paris? The distance which separates both cities is 5 400 km and the radius of the Earth is 6 400 km." I don't even know where to start, we didn't learn this. I would assume the...
  44. P

    RF Signals - Radio waves or electrical signals?

    Hi all Sorry if this is quite a basic concept, but I am confused about RF signals. The way I currently understand it is that radio waves in space are an oscillating electric and magnetic field at 90 degrees to each other traveling through a medium. However, when you pass a radio wave into a...
  45. M

    Radio communication from the galaxy's far side?

    Is it at all possible for radio communication to travel from the obscured part of our galaxy to Earth? If so, about how long would it take to reach us? I have an idea for fiction where we're able to receive communications from the far side of the Milky Way, but we can't figure out how to...
  46. L

    Can You Build a Compact Beeping and Vibrating Radio Receiver at Home?

    First, I know nothing at all about this topic, which is why I'm looking for help. I'm interested in building a radio transmitter/receiver like a child locator at home. The difference would be I'd like the receiver to beep rather than the transmitter, if that's even the correct language to use...
  47. A

    Maximum Information transferrable in Radio Waves

    I wondered if people could clear up some misconceptions I have about radio waves. 1) If I have a 800 MHz wave, does this mean 800 Mbits per second can be transferred in theory? Could I not change the amplitude of this wave every 0.00000000125 of a second, So when a receiver is reading it...
  48. W

    How antennas receive AM radio signals

    The greater the amplitude of a given frequency of light hitting an antenna the greater the induced speed of electricity in the antenna? Reply in simple english please.
  49. B

    Understanding the Relationship Between MHz and kHz on Shortwave Radios

    I have a Shortwave Radio that tunes in on Kilo Herts. So my display says 1015 kHz Now if I want to write this out I would write 101,500,000 Hz Now if I am on a Radio that tunes in on MHz and the display says 101.5 MHz Now if I want to write this out I would write 101,500,000 Hz...
  50. C

    Why Isn't My Radio-Controlled Electromagnet Working?

    Hello everyone! Recently, I decided to start building my own home-made projects, starting at a small scale level. The first task I gave myself was to create an electromagnet. In a few minutes... done; beautiful. Easy as eating cake. However, I wanted to (just for the heck of it) make it turn...
Back
Top