Propagation Definition and 487 Threads

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. DrPapper

    Plane Wave Equation Propagation and Oscillation Directions

    Homework Statement Write down the equation for a plane wave traveling in perpendicular to the plane x+y+z=constant traveling in the direction of increasing x, y, and z. Homework Equations From the given information how do I determine the unit vector that goes next to E(0)? How do I determine...
  2. L

    Error propagation with dependent variables

    Homework Statement Based on Microdosimetry theory, trying to figure out error propagation for a lot of quantities that are produced from radiation spectra. I am having trouble finding information on how to calculate and propagate errors when the quantities in my equations are not independent...
  3. B

    Optical Fourier Transform for Propagation

    Homework Statement The complex amplitudes of a monochromatic wave of wavelength ##\lambda## in the z=0 and z=d planes are f(x,y) and g(x,y), redprctively. Assume ##d=10^4 \lambda##, use harmonic analysis to determine g(x,y) in the following cases: (a) f(x,y)=1 ... (d) ##f(x,y)=cos^2(\pi y / 2...
  4. N

    Error Propagation: x/(y-z) Uncertainty

    Homework Statement Suppose you measure three numbers as follows: Homework Equations x= 200. +-2. y= 50. +-2. z= 40. +-2. where the three uncertainties are independent and random. Use step-by-step propagation to find the quantity q= x/(y-z) with its uncertainty. The Attempt at a...
  5. I

    Need clarification on sig-figs and propagation of error.

    Hello, I have a question asking me to find the volume of a rectangular prism. The dimensions are as follows: x = 20 ± 0.2 cm, y = 30 ± 0.2 cm, z = 70 ± 0.4 cm I am asked to report the answer with the correct number of significant figures and include the error. What I have so far: V = xyz =...
  6. 24forChromium

    What is the relationship between T2 and T1 in torque propagation?

    See image. If T_1 and L is known, what is T_2? (T_2 is caused by T_1)
  7. N

    Can a Blast Wave in a Pipeline Outrun HMX Detonation Velocity?

    I'm a little rusty on my physics, so here's the hypothetical: Put HMX prima cord in a long pipeline , say 1000m. If you detonate the prima cord and the pipe has a 3" ID, would the blast wave outrun the HMX detonation velocity of 9100 m/s. If you reduced the ID of the pipe, is there a certain...
  8. F

    Wave propagation with water moving

    Homework Statement Suppose a person is fishing and is bobbing the fishing pole in constant intervals, there are 2 fish in the water located in the same distance L from the fishing pole (the source of the wave). Suppose also the water is moving from A to B. Which fish will feel the wave first...
  9. O

    Unit conversion - stress-wave propagation speed

    Dear Friends, The stress-wave propagation speed is calculated using : sqrt (elastic modulus/density) The unit of elastic modulus is GPa, and that of density is gram/cm^dim Can anyone please tell me how I can convert the resulting value to m/s (meter/second)? Regards
  10. Jacekmai

    Electric current propagation through living tissue

    Wave propagation speed or velocity of propagation (VoP) of a transmission medium is ratio at which the wavefront of the signal passes through the medium to the speed of light in vacuum. For example, copper has a wave propagation speed ~0.951. What is a wave propagation speed through a living...
  11. T

    Error propagation when using modulus operator

    Sorry if the answer is very simple, but I just had a question regarding error propagation when using a modulo operator in intermediate steps. For example, I have ## \theta = arctan(\frac {A}{B}) ## and then I do ## \theta ## % ##2\pi## (modulo ##2\pi##). This gives me an answer between ##...
  12. H Smith 94

    Understanding propagation loss: What does this output mean?

    Hi there! I am currently building a simulation to model the propagation of radio waves in seawater in terms of its propagation loss. I have previously discussed the models I've looked at but have settled on a model which depends primarily on the propagation distance ##r##, the carrier wave...
  13. H Smith 94

    How is radio wave propagation modelled in seawater?

    Before I start, I apologise for the information dump that is to follow. I don't expect all questions to be answered or all models to be addressed; I simply feel it is appropriate to provide the community with my current knowledge and stage of research so you may not have to search for it...
  14. S

    Wave frequency and propagation attenuation

    In my memory, the wave frequency will decrease because the attenuation in wave propagation, is that true? Can someone please give me some links to prove or disprove it? thanks
  15. ddd123

    Aharonov-Bohm information propagation

    I hope I've searched the forums thoroughly enough, I didn't find a similar question. I'm wondering about the specifics of the speed of the information on change in B of the solenoid between the two paths in a double-slit setup, one large enough where relativistic speed effects are within a...
  16. P

    Error Propagation with Log2 Concentration: Fluorescence Measurement

    Hi there, I have a quick question to report some numbers on an experiment. I made measurements of fluorescence in a titration of a chemical. The titrations were 1:2 serial dilutions so I report each fluorescence as a function of the log2 concentration: concentration chemical x: 1 , 0.5, 0.25...
  17. Gh778

    Delay of propagation of the pressure in a fluid

    Homework Statement Does the delay of propagation of pressure gives a torque during a short time ? A disk full of a liquid turns at a constant angular velocity w around the red axis. At a time, a valve move out, this will increase quickly the pressure inside the liquid. 1/ Draw the lines...
  18. S

    Electromagnetic waves point to point propagation

    Is there a theoretical way to force electromagnetic waves transfere energy point to point like electricity instead omni-dirrectionally? I think it might be helpful for looseles wireless energy transfere.
  19. Aristotle

    Finding the Uncertainties in Frequency with Given Capacitor and Inductor Values

    Homework Statement I am given a frequency value of 95 GHz (9.5x10^10 Hz), C= 25 F, L=1.12x10^(-25) H. The question is to find the uncertainties in frequency by taking account of inductor being 5% accurate & capacitor being 8% accurate. Homework Equations I believe this is the correct formula...
  20. H

    Finding propagation speed/wavelength from an equation

    Homework Statement A wave is described by y=12sin(4t-8x). What is its propagation speed? A. 0.2 B. 0.5 C. 4 D. 8 E. 12 Homework Equations v=wavelength/period v=wavelength×frequency The Attempt at a Solution period= 2π/w=2π/8=.7853 But confused on how to find the wavelength?
  21. J

    Acoustic Impedance - Ultrasound Propagation in Tissue

    Hi, I was just wondering why, when the acoustic impedance mismatch is so high between two boundaries at an interface, most of the ultrasound is reflected back. I was just wondering why this happens which I can't seem to find much of an answer to. The only thing I can think of is refraction and...
  22. I

    Error propagation - partial derivative?

    I am getting a little confused on which error propagation to use: I am looking to calculate the error in B*Cos(θ) , for the vertical axis of a williamson hall plot. where B is fwhm of a peak with it's own error and cos of the bragg angle I am unsure of whether i need to use partial derivative...
  23. jerromyjon

    Sound wave propagation and doppler shift wrt the medium

    In contemplation and research regarding another thread's question about the asymmetry of doppler shift wrt the medium, I find myself trying to imagine two people talking... or perhaps better yet matching pitch. In still air with both people facing each other at ten paces of course they would...
  24. Essence

    Wave speed dependent on medium not source?

    Homework Statement So in my textbook it says "The speed of the wave depends on properties of the medium, not on the motion of source or observer. An explosion causes pressure variations in the air around it. This "deformation" propagates outward as a sound wave at a speed dependent only on...
  25. A

    Propagation of error: exponents

    Hi all. I have been trying to understand propagation of error of exponents. Most an. Chem textbooks I see say y = a^x, sy/y = (sa/a)*x. But say y = a*b, then sy/y = ((sa/a)^2 + (sb/b)^2)^.5 . if a = b then sy/y= (2*(sa/a)^2)^.5 = 2^.5*abs(sa/a). This shows the rule y=a^x, sy/y= x^.5*abs(sa/a).
  26. J

    Backward-wave propagation in Metamaterials?

    Ok so I am currently doing a research project on reconfigurable polarization sensitive metamaterials. Namely trying to manually control/determine where electrical and magnetic resonance within the structure will occur dependent on geometrical parameters, so it can then be used with some active...
  27. Jesus

    Superluminal propagation of fields

    I am reading about the Velo-Zwanziger problem in which particles with spin higher than 1 propagates faster than light when the particles are coupled with an electromagnetic field. In the original paper: G. Velo and D. Zwanziger, “Propagation And Quantization Of Rarita-Schwinger Waves In An...
  28. fluidistic

    TEM mode propagation between 2 infinite conductor plates

    Homework Statement I am trying to solve a problem from Jackson's book (in chapter 8). I must describe the propagation of a TEM mode through a transmission line that consists of two infinite conductor plates that are parallel to each other and separated by a distance a. There's a dielectric...
  29. F

    Error propagation for a sum of means

    I have a = {a1, a2, .., a1000}, where this set forms a distribution of photoelectrons (pe) seen by a particular photomultiplier tube (pmt) over 1000 repeated events. I then have N sets of these (N pmts), each containing 1000 pe values which I believe are indeed random and independent. So a, b...
  30. fissionary

    Understanding Wave Propagation in a Medium

    I read somewhere that for a wave traveling in a medium a particle (of medium) "gives"(I am not sure if that is the right word) energy to adjacent particle.Is this correct? And if it is why and how does this transfer take place? Also what role does inertia of particle play in wave propagation?
  31. I

    A good introduction on light propagation mode

    Hi, Can anyone explain or point to a good introduction in simple terms the concept of 'light propagation mode'? I am in my final year at high school and need to write a research report on how optical fiber communication systems work. The report needs to include some contents beyond what is...
  32. P

    Error Propagation: Dividing By 20 in Pendulum Timing

    Homework Statement suppose i measure the time t for 20 oscillations fro a pendulum. the period is T. Homework Equations Since T = t / 20 delta T = delta t right? The Attempt at a Solution since the 20 is a numerical value, it does not come in the error propagation, does not? when i used the...
  33. BiGyElLoWhAt

    Carrier particles and E-Field Propagation

    A thought experiment that is a consequense of a question someone asked in my particle physics class: We place an isolated electron. We wait 10 years, and place a half ring of electrons (spaced far apart from each other, but uniform) 10 LY away from our central e. Will our charges move? If so...
  34. 5

    Error Propagation for Tube Volume

    Homework Statement You have a cylindrical tube for which you know the length is 16±0.1 cm and the radius is 8±0.1 cm, what is the error of the volume? Homework Equations The Attempt at a Solution V = π*82*16 = 3216.99 cm But since the r term is squared, must we account for its error twice...
  35. T

    Pressure Propagation through Fluid

    I have been searching for an explanation of how a change in pressure propagates thru a fluid to become isotropic. My question is that if the time scale measured is small enough ( much less than the distance divided speed of sound ) will we see the pressure change have an initial direction and...
  36. S

    Error propagation for non-normal errors

    I have several measurements taken over a time series. Each data point has a standard error value. I need to sum up the data points, and determine the error associated with that sum. The error values across the time series are non-normal, so I'm assuming that I can't use the usual error...
  37. L

    Thought experiment on magnetic field propagation

    Some 30 years ago I learned in the elementary school, that if I move a permanent magnet in a coil which ends are somehow electrically closed, than I need to apply force on the magnet, because the generated current creates a magnetic field which is against the magnet's field. However if the...
  38. L

    How Do You Calculate Signal Propagation Velocity in Transmission Lines?

    Hello, I'm stuck on how to find the propagation velocity of the signal in the Line as stated in Question C on the attached image below. 1. Homework Statement Table one (in the attached image) shows typical values of Z and Y for an overhead line and underground cable. Please note that this is...
  39. J

    Propagation of electromagnetic wave

    will the distance traveled by an em wave depends on temperature,if so then explain
  40. Akash Pardasani

    Propagation of de Broglie waves

    I had a doubt regarding the propagation of de Broglie waves. How do we know the speed of propagation of these waves and also do there characteristics( speed and amplitude and frequency) depend on the source particle ( or they depend only on the motion(momentum) of the source and no whatsoever...
  41. T

    Computation of propagation amplitudes for KG field

    Note: I'm posting this in the Quantum Physics forum since it doesn't really apply to HEP or particle physics (just scalar QFT). Hopefully this is the right forum. In Peskin and Schroeder, one reaches the following equation for the spacetime Klein-Gordon field: $$\phi(x,t)=\int...
  42. X

    FDTD of (ultrasound) wave propagation through muscle

    Im a mechanical engineering student currently, with a third year project of simulating ultrasound propagation through the abdomen. Currently i just want to simulate it going through muscle with no obstacles. I don't really understand where to start, I have formed some equations based on the wave...
  43. N

    Does Time Delay Affect the Curl of an Electric Field?

    I am thinking about the curl of the electric field and want to make sure I have something straight: Say you have a charged particle moving along some prescribed path. The electric field propagates outward at speed c, leading to a "retarded" time that you need to calculate in order to get the...
  44. S

    Radio wave propagation in water

    I'm trying to get my head around radio wave propagation in conductive media such as water, saturated rock, etc. What I know is that propagation is poor but better at lower frequencies and this has something to do with "skin depth". I have read what I can on skin depth but I struggle to relate it...
  45. J

    How to calculate error propagation for several measurements?

    I'm having trouble with error propagation analysis. When you make a single measurement of several variables, say (x,y,z) and you calculate a function f(x,y,z), you just have to apply the common formula of error propagation: $$\sigma_f(x,y,z)=\sqrt{\left| \frac{\partial f}{\partial x} \right|...
  46. D

    Understanding Propagation of DC Current Along a Conductor

    I've been stuck on what I would of thought was a simple/common question but I can't seem to find an answer anywhere. I'm confused as to how a DC current propagates along a conductor (wire) in terms of it's E/H field. I understand that it is these fields that cause the propagation of current...
  47. S

    Error Propagation and Uncertainties in Parameters

    There is a quantity (W) that I would like to calculate that is, ultimately, a function of parameters that I can measure directly (a and b), W = W(a, b) But I cannot measure a and b perfectly, there will be some uncertainty in these measurements. This uncertainty will propagate into my...
  48. P

    The propagation of disturbances in interstellar gases

    Homework Statement Show that the solution of the form ρ1 = ρ1(x±a0t) satisfy the equation: ∂2ρ1/∂t2 - a02∂2ρ1/∂x2 = 0 and that they correspond to waves propagating in the directions x increasing or decreasing. Homework Equations P = P0 + P1 ρ = ρ0 + ρ1 u = u1 The Attempt at a Solution P1 =...
  49. T

    Results from TLE & SGP4 propagation - don't seem right & with interpretation

    Greetings all ! I have this problem with SGP4 propagation, that I hope someone can help me out with. I acquired a TLE of the ISS from internet and used the C++ SGP4 propagator to compute future position and velocity vectors of the Station. I am unsure about some aspects of results though and...
  50. T

    C/C++ How to write C++ code using SGP4 to propagate satellite position

    Greetings all ! I really hope this is the right sub-forum for my question, I have chosen it because I've seen TLE being mentioned a couple of times around here. I have done some reading on astrodynamics and orbital mechanics, but I am relatively new to coding. I would like to write some C++...
Back
Top