I’ve seen radio waved depicted in two different ways that seem at odds with one another. the first is something like [this](https://upload.wikimedia.org/wikipedia/commons/thumb/3/3d/Wireless_tower.svg/75px-Wireless_tower.svg.png), with the waves spreading out from a point source in all directions. the second is like [this](https://upload.wikimedia.org/wikipedia/commons/thumb/d/d1/Cross_linear_polarization.gif/330px-Cross_linear_polarization.gif) with the radio wave moving in a “tube” constrained by its own parameters.
since we can’t see them, radio waves remain a bit abstract, but both of these visualizations can’t be correct at the same time… or can they? can someone as to what the real picture would “look” like?
many thanks!
In: 3
First is picturing omni directional. Blasting in all directions. 2nd is point to point, but just a visual representation of what the emf is doing over time and possibly trying to show different polarization. Not sure though TBH that image is near pointless IMO.
The first is just a symbol and is not an accurate description of what is going on. Rf heat maps can show you what the rf “looks” like. Omni directions look like a Gerber daisy. Diretional Point to point look like a freanch fleur-de-lis (New Orleans saints symbol). Semi directional, point to multi point, is like a faned out version of point to point.
Radio waves don’t “look” like anything because they’re not a physical thing – they’re just oscillations in the electric and magnetic fields. Anything you see what depicts radio waves like is either an artistic expression that’s not meant to be correct in any way (the first link) or a mathematical model that depicts how radio waves (and all other electromagnetic radiation) *work* but not what it looks like. There are countless ways to mathematically model electromagnetic waves or just to illustrate them, but ultimately, radio waves aren’t physical, tangible things and thus don’t “look” like anything in the first place.
They are both correct hey just illustrate different things. Radio waves are types of photons like light.
You know when you light up a lightbulb you know its shooting billions of tiny lasers out in all directions, and you could draw that as either a glow/circle, or a bunch of tiny lines (like when you draw someone having an idea)? Its like that. So its billions of tiny lines which are so dense its very frequently drawn as a sort of radial wave thing.
A radio tower is basically just a big lightbulb but for a very different frequency of light.
One visualizes how they propagate.
You shake the electromagnetic field with your antenna, and this will propagate at the speed of light to everything in sight, bounce around and reach places that are not in visual range. It’s like emitting light. The antenna makes invisible radio “light”.
To be more precise, light is a type of electromagnetic signal. And color is the frequency. Radio waves are from the same family, but are not visible to humans.
So, when your tv receives a tv channel, your tv antenna is seeing the transmitting antenna “changing color” and the tv just transforms that to visible light and put it on screen. (Oversimplified).
The second is what a wave is compared to time.
When you study electromagnetic things, they are invisible and go at speed of light. To make it visible to us, we depict it like a still picture. It’s like if you study the ocean waves, you take a picture of the ocean, show it to people and then show them how the wave is made. You froze it in time to be able to have a still image to explain. Or you make an animation. Everything but showing it at speed of light because that a bit too fast.
I gave it a try. Hope it helped. Sry but that’s a bit difficult to put down in few words.
The second image is slightly more correct, but both are reasonable depictions. The point source of the first image is sending out so many individual waves in all directions that, in practice, it is essentially producing an omnidirectional spherical “wave”.
It’s like the sun – for all practical purposes the sun emits light in all directions continuously, but technically it’s just emitting an unfathomable number of discrete photons.
Any depiction that shows a squiggly line is abstract – the wave follows a straight path.
The line represents the strength of local fields, and is no representation of the actual movement or physical shape of the radio wave.
A wave cannot be perfectly constrained to a beam, but with shorter waves and wider beams, you can get pretty close. Radio waves really don’t form good beams, because the waves are so long, but you can point them roughly in one direction. That’s what big satellite dishes do.
Regular antennas actually also limit the direction – the antenna does not transmit in the direction it’s pointed. It *only* transmits sideways.
It depends on the transmitting antennae. If it is ‘omnidirectional’ then the waves will appear to propagate in all directions.
Think of the difference between a lightbulb and a flashlight. The flashlight focuses the light from a lightbulb so it goes in one direction. It is a similar idea with point to point antennae.
[https://www.youtube.com/watch?v=ZaXm6wau-jc](https://www.youtube.com/watch?v=ZaXm6wau-jc)
This engineering video is helpful to understand how antenna work.
The second one isn’t a visualization, it’s a graph (plot) of the electric field vector as a function of distance. The radio wave propagates in a straight line, but it’s made up of electric & magnetic fields whose orientations are perpendicular to the direction of travel.
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If you throw a rock into a pond a fish under the water would see the ripples as circular waves radiating away from a point source, but an insect floating on the surface of the water would perceive the ripples as a linear wave in time. Both views are simply different perspectives of the same thing. In the second visualization the “tube” isn’t a constraint but rather signifies that it’s a local observation of the underlying EM field.
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