What is Propagation: Definition and 487 Discussions

Radio propagation is the behavior of radio waves as they travel, or are propagated, from one point to another, or into various parts of the atmosphere. As a form of electromagnetic radiation, like light waves, radio waves are affected by the phenomena of reflection, refraction, diffraction, absorption, polarization, and scattering. Understanding the effects of varying conditions on radio propagation has many practical applications, from choosing frequencies for international shortwave broadcasters, to designing reliable mobile telephone systems, to radio navigation, to operation of radar systems.
Several different types of propagation are used in practical radio transmission systems. Line-of-sight propagation means radio waves which travel in a straight line from the transmitting antenna to the receiving antenna. Line of sight transmission is used for medium-distance radio transmission, such as cell phones, cordless phones, walkie-talkies, wireless networks, FM radio, television broadcasting, radar, and satellite communication (such as satellite television). Line-of-sight transmission on the surface of the Earth is limited to the distance to the visual horizon, which depends on the height of transmitting and receiving antennas. It is the only propagation method possible at microwave frequencies and above.At lower frequencies in the MF, LF, and VLF bands, diffraction allows radio waves to bend over hills and other obstacles, and travel beyond the horizon, following the contour of the Earth. These are called surface waves or ground wave propagation. AM broadcast stations use ground waves to cover their listening areas. As the frequency gets lower, the attenuation with distance decreases, so very low frequency (VLF) and extremely low frequency (ELF) ground waves can be used to communicate worldwide. VLF and ELF waves can penetrate significant distances through water and earth, and these frequencies are used for mine communication and military communication with submerged submarines.
At medium wave and shortwave frequencies (MF and HF bands) radio waves can refract from the ionosphere. This means that medium and short radio waves transmitted at an angle into the sky can be refracted back to Earth at great distances beyond the horizon – even transcontinental distances. This is called skywave propagation. It is used by amateur radio operators to communicate with operators in distant countries, and by shortwave broadcast stations to transmit internationally.In addition, there are several less common radio propagation mechanisms, such as tropospheric scattering (troposcatter), tropospheric ducting (ducting), and near vertical incidence skywave (NVIS) which are used in specialized communication systems.

View More On Wikipedia.org
Recent contents Top users
  1. B

    Electromagnetic wave propagation

    Please consider a plane wave that propagates through a dielectric with friendly properties (isotropic, non-conducting...) with speed c/n. What would happen if we remove the dielectric and the wave continues to propagate in empty space?
  2. M

    Treating Propagation of Errors in $R^n$ to $R^m$ Transformations

    I want to know how to treat propagation of errors in general. When the transformation of variables is a transformation of $R^n$ to $R^n$ it simply involves a jacobian: g(\vec{y}) = f(x(\vec{y}))|J| With J_{ij} = \frac{\partial x_i}{\partial y_j} (see...
  3. N

    How Does an Electric Field Propagate Through Wires?

    hi! Can anyone explain how an electric field propagates from one point to another? For example if i touch two 6ft wires to the ends of a 5V battery, i'll get 5V across the end of the wires after a propagation delay. How does the electric field (voltage) of the battery make it's way down to...
  4. H_man

    Error Propagation in Trigonometric Functions

    Homework Statement I can't seem to find online how to calculate the error propogated by trigonometric functions. That is, I know the uncertainty in \theta but am not sure how to deal with it when I apply the tan function. I am quite okay with how to deal with all the basic...
  5. V

    Using propagation delays to my advantage?

    Hello, I am currently using a 555 timer to check the period of a square wave input: The timer is triggered off the leading edge of the first square pulse, and if a second leading edge is detected OR the 555 becomes untriggered then a clock signal will be sent to a D flip flop and its state...
  6. Loren Booda

    Does the Wavefunction Propagate at Finite Speed or Instantaneously?

    When does the wavefunction propagate at a finite speed, and when instantaneously?
  7. C

    E&M wave propagation and polarization

    Hi, all, My question is if I have two plane E&M wave traveling in the x-z plane, and they are polarized along the y direction, and I know that there is an angle theta between their propagation vectors, how do I set up the equations to get the intereference pattern in the z direction? I...
  8. S

    Solving Wave Packet Propagation: Analyzing Group and Phase Velocities

    Consider a wave packet represented by \Psi (x,t) = \int_{k-\Delta k}^{k+\Delta k} A \cos\left[k'(x-ct)\right] dk' A constant and ck' is the dispersion relation SOlve th integral and describe teh propogation properties of this wave packet. Assume this means that the phase and group...
  9. M

    Resistance Propagation of Error

    We recently did a Resistance in Circuits lab. My coded resistances were 33, 100 and 220. The measured resistance was 33.3, 101.6 and 219 So we did 3 setups. (Series, Parallel and Combination) Series = 351.8 measured ohms Parallel = 22.5 measured ohms Combinations = 101.5 measured...
  10. L

    Propagation of uncertainty calculations

    I hope this is the right place for this... Well, I have a lab where we measured the charge/mass ratio of an electron using a helmholtz coil and vacuum tube. I need to calculate the propagation of uncertainty in my final value. The formula for calculating the e/m ratio is the following...
  11. K

    Solving Wave Propagation & Particle Speed Problems

    Hi! If anyone could help me with this problem I'd be deeply appreciative: Speed of Propagation vs. Particle Speed. The equation y(x,t)=A cos2(pi)f (x/v - t) may be written as y(x,t)= A cos[(2(pi)/lamda)(x-vt)] a) Use the last expression for y(x,t) to find an expression for the transverse...
  12. F

    What Is the Minimum Radius Needed to Paint on a Cube to Contain Light?

    Lets say you got a glass cube and a small light source embedded at the exact center of the glass cube. Now if you want to paint a circle on each face of the cube so that the light is prevented from leaving the cube, what is the minimum radius of the circle that you need to paint? Let say...
  13. P

    Velocity of propagation in lossy media

    regarding plane waves theory and their properties, for lossy media (conductors) in different books appear a formula that represent alfa y beta constants in the followig way: alfa = beta = root square( pi*frequency*mu*sigma) valid for good conductors (high loss material) I have checked...
  14. S

    Sound Wave Propagation problem

    Problem: The equation of a certain traveling transverse wave is y(x,t)=4.00sin(81.0(pi)t - 1.590(pi)x) where t is in seconds and x and y are in cenimeters. Find the speed of propagation, the period and the wavelength for these waves (express you answer in units of m/s) So, I know A...
  15. somasimple

    Wave propagation in elastic tubes.

    Hi All, Here is my question regarding the solution of this little movie => http://www.somasimple.com/flash_anims/ap_003.swf A thin elastic tube (thickness = 1) is connected with a thicker one (40 times thicker than the previous section). The tubes are poured with water. A wave is is traveling...
  16. B

    Isotropic and anisotropic propagation of light

    Do you aggree that there is an inertial reference frame in which light in free space propagates isotropically whereas in all other inertial reference frames its propagation is anisotropic?
  17. E

    How Do Charges Interact Through Photon Exchange?

    charge and its "propagation" if we imagine a charge. Now other "charges" can sense the presence of this charge when they are sufficiently close. This is due to temporary photons? Could some explain in a simple manner how this works? Take electric charges for instance.
  18. B

    How does light travel through air molecules?

    This might be a stupid question but, taking a shower yesterday, I was wondering how is light propagating through the air molecules. For example, take the light coming from a distant star entering our atmosphere. Between my eyes and the star there are billions of air molecules. How do the photons...
  19. D H

    Attitude propagation stability and accuracy

    I am verifying and validating a rotational state propagator used in a dynamic simulation package. I have found some problems and solutions to them. This post outlines the propagation, the problems, and the solutions. Some questions before I start: - Has anyone else analyzed stability and...
  20. M

    Engineering Confused how do you calculate propagation delay of circuit and paths?

    confused! how do you calculate propagation delay of circuit and paths? Hello everyone, this book explains literally nothing about propgatation delay and how to calculate propagation delay of gates and the paths. And yet one of the questions says...
  21. B

    Error Propagation for F=4*pi^2*r*m/T^2

    I know there is a formulas for doing error propagation with separate formulas for when dealing with powers, multiplying/dividing, and adding/subtraction. What about if I have the formula F=4*pi^2*r*m / T^2...? Also should i do error propagation for the varibles in the formula r (radius), and...
  22. E

    What is the behavior of electric field propagation in closed and open circuits?

    Hi, I'm trying to get my head around electric field propagation in an electric circuit. If you have a battery with no circuit I imagine the electric field between the terminals would look like the magnetic field lines between the two poles of a magnet. What I can't visualize is what the field...
  23. S

    Calculating Wavelength of Light in Glass Slab

    Hi! I was wondering if you can give me some adivice on how to approach this problem: In a physics lab, light with a wavelength of 560 nm travels in air from a laser to a photocell in a time of 16.5 ns. When a slab of glass with a thickness of 0.860 m is placed in the light beam, with the...
  24. P

    Calculating Characteristics of a Sinusoidal Wave Propagating on a String

    probably easy question a sinusoidal wave is propagating along a string in the +x direction. 10 waves pass by a point every 10 microseconds. the wave exhibits the following characteristics: a) at t=0 and x=0 , the wave propagation speed is 30 m/s, and the Oscillation speed is 2.5 mm/s in...
  25. P

    How Should I Space the Heights to Minimize Error?

    I was collecting data for a simple physics lab today when I stumbled upon a question I couldn't answer. Very basically, the lab consisted of measuring the time it takes a ball to drop a variety of distances, between 0 and 100cm. By plotting \frac{y}{t} vs. t (where y is height and t is...
  26. M

    Sounds propagation in different mediums

    I am utterly confused with this problem, I am not quite sure how to formulate an equation to solve for the answer : The speed of sound in steel is about 4.2 kilometers per second. A steel rail is struck with a hammer, and there is an observer some distance away with one ear to the rail. The...
  27. Loren Booda

    What causes a single photon to propagate in an infinite spacetime?

    Imagine a massless, classically zero curvature, infinite spacetime in which propagates a single actual photon. What eventually motivated this photon to propagate, and does its trajectory or energy vary due to the spacetime vacuum energy?
  28. S

    Propagation of errors? (lab phenomenon question)

    propagation of errors? (lab "phenomenon" question) In our lab, we are measuring the acceleration due to gravity. We do this by dropping an object through a photogate, which records position vs. time data as the object falls. From this position vs. time data, the computer uses derivatives to...
  29. Clausius2

    Heat Equation: Understand Propagation of Heat

    Well, this is my question. It's something like a philosophical thinking. Look at this problem of the Heat Equation: \frac{\partial T}{\partial t}=\alpha \frac{\partial^2 T}{\partial x^2} with: 0<x<L T(x,0)=g(x) and T(0,t)=T_1 T(L,t)=T_o This is a parabolical PDE...
  30. C

    Error Propagation: Solutions to Complex Equations

    Always the easy things we forget... I know how errors propogate through multiplication or division when every term has an error, but how do I propagate errors in equations when only one term has an uncertainty? I want to say just multiply and divide the uncertainty value by the constants, i.e...
  31. M

    “aumic” theory and the propagation of light.

    I am starting a new thread on this subject because I feel that the subject under discussion is of the greatest importance. The “aumic” theory on the nature of light brings to our attention , for the first time , several peculiar and interesting aspects on the nature of light and indeed of all...
  32. V

    False Claims of Gravity Propagation Limit

    Ed Fomalont of the National Radio Astronomy Observatory and Sergei Kopeikin from the University of Missouri in Columbia, performed an experiment on 18 September 2002 using an array of radio telescopes around the world they observed light from a faraway galaxy bend as the planet Jupiter passed...
  33. R

    Is the Speed of Light Different in a Casimir Vacuum?

    Hellfire, you just going to make chroot :mad: Whilst you queastion and reasonning are quite sound, the response by chroot is not so. So let me elaborate on this:In quantum field theory, particles (and thus also photons) are excitations of fields. The the position is not a dinamical...
  34. H

    Light Propagation in Quantum Field Theory

    In special relativity it is often claimed that light does not need a medium to propagate. In quantum field theory, particles (and thus also photons) are excitations of fields. The the position is not a dinamical variable as such anymore, but just a label for each of the field excitations in...
  35. U

    Propagation of all fields the same.

    That is to say that light propagates at the same speed as a gravitational wave. However the gravitaional wave gives location of it's source at an almost instantaneous fashion, while a photon gives it's location when it slaps you cross the face with the source. In an example with the sun and...
  36. N

    What is the ideal wavelength for propagation in optic fibres?

    I was asked this question Why is there an ideal wavelength for propagation in optic fibres? a. Light absorption losses are minimum b. The fibre has its greatest transparency at the ideal wavelength c. Rayleigh scattering is greatest at this wavelength d. Total internal reflection...
  37. R

    Propagation of Single Photon - Richard's Question

    When a single photon is produced by a point source, and detected by an array of detectors placed on the surface of a sphere around the point source, would only one of the detectors pick up the photon, or would only some of them pick it up, or would all of them pick it up, assuming no extraneous...
Back
Top