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. O

    A Measurement and error (error estimation and propagation)

    Description of the situation I have measured the incident number of electrons in a channel electron multiplier at different light polarization angles (a photoelectron angular distribution measurement). The events follow a poisson distribution and as far as I know the number of electron counts in...
  2. Vaibhav Sahu

    Propagation of EM Waves in metamaterials

    We have materials that have negative effective permittivity and permeability. In such materials, when the product of permittivity and permeability is negative, solving the wave equation yields a wave with a purely imaginary wave number. Does this mean complete attenuation of the wave ?
  3. E

    I Dispersion: expansion of wavenumber as function of omega

    Hi! Dealing about wave propagation in a medium and dispersion, wavenumber k can be considered as a function of \omega (as done in Optics) or vice-versa (as maybe done more often in Quantum Mechanics). In the first case, k (\omega) \simeq k(\omega_0) + (\omega - \omega_0) \displaystyle \left...
  4. P

    I Similarities / diffs between diffusion & wave propagation

    Hi, I'm a second year undergrad and we've covered the heat equation, \begin{equation} ∇^{2}\Psi = \frac{1}{c^{2}}\frac{\partial^2 \Psi}{\partial t^2} \end{equation} and the wave equation, \begin{equation} D∇^{2}u= \frac{\partial u}{\partial t} \end{equation} in our differential equations...
  5. M

    Particle Velocity and adiabatic/isothermal propagation

    This is a question that has been bugging me for a little while. If sound propagation in air changes from an adiabatic to an isothermal process (for example via the use of fiberglass or other heat conducting material), the wave velocity is lowered due to the reduction in the bulk modulus of air...
  6. Lord Crc

    Observation of laser pulse propagation in optical fibers

    Just wanted to share this, mainly because I really liked the videos (found in the supplementary section at the end). Moderators, feel free to move it to a more appropriate place. Observation of laser pulse propagation in optical fibers with a SPAD camera Recording processes and events that...
  7. E

    Group delay with Gaussian pulse

    Hello! Starting from a gaussian waveform propagating in a dispersive medium, is it possible to obtain an expression for the waveform at a generic time t, when the dispersion is not negligible? I know that a generic gaussian pulse (considered as an envelope of a carrier at frequency k_c) can be...
  8. H

    A Uncertainty Propagation of Complex Functions

    Suppose I have some observables \alpha, \beta, \gamma whose central values and uncertainties \sigma_{\alpha}, \sigma_{\beta}, \sigma_{\gamma} are known. Define a function f(\alpha, \beta, \gamma) which has both real and complex parts. How do I do standard error propagation when imaginary...
  9. G

    I Circular electron propagation in carbon nanotubes?

    Can carbon nanotubes support electron propagation perpendicular to the axis? That is, can there be circular current flow on the tube's perimeter, not just the linear flow parallel to the axis? Because I reading that it's generally considered a 1-dimensional conductor.
  10. H

    A Uncertainty Propagation in Coupled Oscillator

    I am a senior physics and mathematics major, and this is my last semester. As a result, I am taking advanced physics lab, which feels more like a grad school experiment than an undergrad. One of the labs deals with the modal analysis of three spring-mass systems placed vertically as shown in the...
  11. F

    Ti:sapphire: laser propagation

    Hello :) I have 2 questions about the beam propagation of an Ti:sapphire-laser: Picture 1: The cw argon ion laser brings the beam to mirror (1). Then...? Then the beam (100% of it), go to the birefringent plate (4), gets then reflectet to the first mirror again (1) , which reflects it to the...
  12. C

    Is the electromagnetic propagation time asymmetrical?

    For a point in space if we have the values of E and H fields at a certain instant of time, we can tell the direction of the propagation of these values, which is the direction of the cross product vector E x H. Is this phenomenon time asymmetric or not ?
  13. C

    How to code ultrasonic beam propagation

    Does anyone have an open source code or know how to code propagation of multi gaussian beams through multiple interfaces using the ABCD matrix approach? And this is using ultrasound and not optics. Please let me know if anyone can help out in this
  14. E

    Maxwell's/Faraday Law Concern Propagation of Induced Fields

    The integral form of Maxwell's equation pertaining to induced electric fields is: ∮E(t0)⋅dℓ= −dΦ(t)/dt|t=t0Say for a long time, in some circular region there has been no B or E fields present. Then, there is a sudden constant increase of B field introduced in the middle. I know that information...
  15. F

    B Simple error propagation questions

    Hi, I'm looking at an Italian high-school physics textbook. The subject is uncertainty propagation, and the target is 9th grade students. The book is allegedly by J.S. Walker, but I'm not sure how much it was "redacted" by the Italian editor. I am a little puzzled by two rules that are stated...
  16. F

    Error propagation (tape shorter than measured length)

    Homework Statement The problem is about calculating the error on the area of a rectangular field. What is known is that the sides of the rectangle are 120 m and 180 m, and they have been measured with a 10 m measuring tape. The tape has a sensitivity of 2 cm.Homework Equations Since the area...
  17. binbagsss

    QFT Wicks theorem contraction -- different fields terms of propagation

    Homework Statement I am trying to express ##T(\phi(x1)\Phi(x2)\phi(x3)\Phi(x4)\Phi(x5)\Phi(x6))## in terms of the Feynman propagators ##G_F^{\phi}(x-y)## and ##G_F^{\Phi}(x-y)## where ##G_F^{\phi}(x-y) =\int \frac{d^{4}k}{(2\pi)^{4}}e^{ik(x-y)} \frac{ih}{-k.k - m^2 -i\epsilon} ## and...
  18. E

    Error propagation - inverse of an error

    Homework Statement Let t = f(g, h, A, Δm, Γ, r). For t = 2 s, the propagated error is σ = 0.02 s. Can the error of 1/t2 be simply determined using the known error in t = (2 ± 0.02) s, or must the variance formula (with all the partial derivatives and errors of each dependent variable) be...
  19. A

    I Photon absorption and speed of wave function propagation....

    Hi all, Whew, last question for a while: I think I already know the answer, but want to confirm (e..g, I think this thread basically answers the question, https://www.physicsforums.com/threads/propagation-of-wavefunction.152053/) As an example, let's say I have an electron (in free space or...
  20. G

    Propagation of Uncertainty - Hollow Cylinder

    Hi, I'm having quite a bit of trouble finding the propagation of uncertainty (using partial derivatives) of the volume of a hollow cylinder. The examples in my tutorial only demonstrates how to find the propagation of uncertainty on simple operations such as x + y, x/y, etc... 1. Homework...
  21. B

    A Exploring Spacetime Propagation in Higher-Dimensional Relativity

    What kind of spacetime structure can make the lines of a soliton-like field propagate in higher-dimensional space-time that do not diverge as they converge on the target. Does General Relativity make this just completely impossible? Or is there a solution of General Relativity that allows this...
  22. S

    A Imaginary time propagation to find eigenfunctions

    Hi, I have been trying to use imaginary time propagation to get the ground state and excited states eigen function but the results I got is different from the analytical solution. I know that to get excited states, I should propagate 2 or more orthogonal functions depending on the number of...
  23. M

    A Does continuous mass distribution implies finite propagation

    speed? This question emerged in my mind while studying a discrete and continuous mathematical model of a falling slinky. In the discrete model, we suppose an instantaneous interaction between mass points at a distance, so the action propagates through the chain of mass points with infinite...
  24. R

    I Propagating Error in both numerator and denominator of ratio

    Hello, I have a set of N samples, each of which yields the measurable variables A and B. I am interested in computing the mean and standard error of the ratio A/B within the group. The catch is that I need to do background subtraction on both A and B, and the two different background values BGA...
  25. B

    I How to Estimate Uncertainty for a Physical Quantity with Dependent Variables?

    I have a physical quantity A defined as ##A=(74.5 B^2*(M+N))^{1/3}## where B, M, N and relative uncertainties are given. And M and N are dependent on B. Could you show me how to calculate and estimation for the uncertainty on A? Thanks a lot
  26. Vajhe

    Computational Resources for learning about Optical Beam Propagation Method (BPM)

    Hi, I'm a physicist intern that has some problems with Optics simulations; I'm very interested in doing some Beam Propagation Method (BPM) simulation, but the information online is not that good for begginers in the area. Can anyone advise me on books, journals or such that might help me learn...
  27. billu

    Flexural Wave Propagation speed

    Hello Everyone, my question is that what's the formula or equation to find flexural wave propagation speed along the beam?? Please guide with this, I am kind of stuck in this problem. Thanks in advance,waiting for the response...
  28. S

    A Weyl Tensor Gravity propagation

    I read Weyl tensor helps on propagating gravitational effects. Ricci is local depending on mass energy at that point and would vanish at other points. Weyl propogates the gravity effects (for example gravity at any point between Earth Moon is due to Weyl Tensor). I didn't quite get it...
  29. T

    I Error propagation of exponentials

    I am just wondering why there is a discrepancy between two different methods for error propagation. For example, if you have ## Q = (a)(b)(c) ## then the relative error in Q is simply the square root of the sum of the squares of each of the terms being multiplied together, correct? But what if...
  30. T

    How does error propagate in a complex equation involving averages and variances?

    Homework Statement Hello, I have the following operation that I want to perform: f=\frac{\bar{X}}{100-\sum \bar{Y}_j}*K \bar{X} and \bar{Y} are averages with variances S_{X}^2 and S_{Y_j}^2 and K is a constant. How will the error propagate? Homework Equations According to...
  31. It's me

    Velocity of propagation of an EM field in vacuum

    Homework Statement In a region of empty space, the magnetic field is described by ##\vec{B} = B_0e^{ax}\sin{(ky-\omega t)} \hat{z}##. Find the speed of propagation ##\vec{v}## of this field. Homework Equations ##\Delta \vec{B} = \frac{1}{v^2}\frac{d^2\vec{B}}{dt^2}## , ##k=\frac{\omega }{...
  32. bcrowell

    I LIGO and speed of propagation of gravity

    Before the recent LIGO result, there was already not much doubt that gravitational effects propagated at c, but the evidence was indirect. To what extent does the LIGO result test this directly, and how will this be improved in the future? The H1 and L1 instruments are separated by 3002 km...
  33. Captain1024

    Electromagnetics: Plane Wave Propagation, Unknown Medium

    Homework Statement Based on wave attenuation and reflection measurements conducted at 1MHz, it was determined that the intrinsic impedance of a certain medium is , and the skin depth is 2m. Determine: a) The conductivity of the medium b) The wavelength in the medium c) The phase velocity...
  34. E

    Another question about dispersion (and wavenumber)

    Hello! I still would like to thank those who participated to my previous thread about group velocity and dispersion. Now there is a (maybe) simpler question. A sinusoidal, electro-magnetic plane wave in the vacuum propagates in a certain direction with the following wavenumber, which is supposed...
  35. M

    Laser Beam Propagation: Calculating Power & Radius

    Hi all, I am interested in finding the power of a laser diode as function of the distance z, assuming a free space propagation. I think to have enough information to work it out but I am stacked at the moment. Given: the initial power, P0 = 1mW beam width clip (e-2 = 13.5%), wx = 3μm, wy =...
  36. N

    Exploring the Propagation of EM Waves: From Sound to Matter and Beyond

    Hi... If we consider propagation of sound through a medium other than vacuum, we mean, when sound is produced by a vibrating speaker diaphragm, it gives periodic jolts to the molecules and atoms present in the medium or air. These "pushes" are transferred to all adjacent atoms until finally few...
  37. T

    What allow matter wave propagation?

    If waves require a medium or some kind of force carrier to propagate, how exactly do matter waves propagate?
  38. F

    A Does QFT specify particle propagation?

    I need to clear up my (mis)understanding about QFT. Does QFT show how a particle propagates through spacetime? (Or maybe this is the realm of QM) Or does QFT only specify how a particle propagates as a particle through time without reference to where in space it is? But... if QFT specifies how...
  39. S

    Propagation amplitude and time-evolution operator

    I know that the time-evolution operator in quantum mechanics is ##e^{-iHt}##. Is this also called the Schrodinger time-evolution operator? Also, can you guys explain why the amplitude ##U(x_{a},x_{b};T)## for a particle to travel from one point ##(x_{a})## to another ##(x_{b})## in a given...
  40. B

    Error propagation and significant digits

    Moderator's note: Thread moved to homework section. Thus no template. I have an exercise in which I have to calculate the Area from the following measurements: L = 22.1 ± 0.1 cm W = 7.3 ± 0.1 cm Of course, A = W * L = 161.33 but since I have a measurement with just 2 significant digits the...
  41. R

    What is the Total Uncertainty in Measuring Force with a 0-10 lbf Load Cell?

    Say I have a 0-10 lbf load cell that can measure the force it takes to lift an object. The load cell is accurate to 1% of the full scale. I take 5 measurements and get the following readings: 5.2, 5.1, 4.9, 5.0, & 4.8, all in lbf. Now I am asked to give the mean with the associated...
  42. L

    About the propagation of sound

    I'm trying to understand how a vibrating body produces oscillations in sound pressure. I've been through derivations and solutions of the wave equation for a string, but I don't understand the transition from waves on a string to sound pressure waves. How are the waves on a string or drum...
  43. DiracPool

    Understanding Photon Propagation: Entity or Quanta?

    What is the most accurate way to think of a photon moving through space? 1) Should we think of it as an entity that travels as an integrated corpuscle that parts the "quark sea" of empty space and maintains it's internal integrity as it moves from point A to point B, or.. 2) Should we think...
  44. Kostik

    Free particle propagation: paradox?

    Shankar ("Principles of Quantum Mechanics", 2nd ed.) shows that the free particle propagator "matrix element" is given by (see p. 153): ## \qquad \langle x | U(t) | x' \rangle = U(x,t;x') = \left(\frac{m}{2\pi\hbar it}\right)^{1/2} e^{im(x-x')^2/2m\hbar} ##, which can be used to evaluate the...
  45. E

    Why is the resonance condition satisfied in a transverse resonance method?

    The Transverse resonance method is used to determine the propagation constant of a wave in several waveguides, like the rectangular waveguide, or also dielectric waveguides. It takes advantage of the fact that a standing wave is present along a certain direction (transverse with respect to the...
  46. Anton Alice

    Propagation of EM-Waves, Independence of B and E, and Grav...

    Hello Forum, I have a lot of questions concerning Wave propagation, but I will not pose them all into one thread, because of my experience, that part of them will be overlooked. So let's get started: 1. Phase shift, E-B- Independence Consider a plane wave generated by a distant dipole...
  47. C

    Error Propagation in Mass Flow Rates

    I tried posting this question in this forum a couple of weeks ago, but didn't get an answer to my question. I'm going to try posting it again using the formatting template so that it is hopefully clearer. I am also not sure if this is the right forum to be posting this in. It is a problem I ran...
  48. H

    Does this wave propagation problem make physical sense?

    Hi, I'm trying to make sense of a wave propagation problem. It's a 1D problem, modelling propagation of density perturbations which travel like waves in a fluid. The problem is governed by the mass and momentum equations and density is related to pressure using the bulk modulus of the fluid...
  49. E

    Why is dispersion important in wave propagation?

    In the propagation of non-monochromatic waves, the group velocity is defined as v_g = \displaystyle \frac{d \omega}{d k} It seems here that \omega is considered a function of k and not viceversa. But in the presence of a signal source, like an antenna in the case of electro-magnetic wave or a...
  50. C

    Error Propagation - Reconciling Two Approaches

    Hi, I am trying to find the error propagated by calculating the sum of a set of mass flow rates collected over the same length of time. The sum of mass flow rates can be calculated with two approaches, since the collection time is the same for all of them. Approach (1) is adding up all of the...
Back
Top