The length of the wave in radio frequencies is in meters. It is greater than microwave which wavelength is in centimeters. At 27.12 MHz in radio frequency, for example, the wavelength is around 11 m. I am just curious on their wave thickness. Anybody here knows this?
You may not understand what a wave is. The wavelength you quote is for an infinitely wide plane wave. This has infinite thickness in both directions perpendicular to the direction the wavelength is measured in. All real waves are narrower than this and have infinitesimally - or sometimes measurably - longer wavelength than this. The width of a wave depends on the width of the source, or on the boundaries of the space it is in.
The wave from a dish antenna starts off as thick as the size of the dish, and (usually) spreads out as it travels further from the dish.
Individual photons seem to be as wide as the beam, because single photon interference effects (Young's slits) can be measured from slots on opposite sides of the beam.
Without boundaries, a wave cannot be less than half a wavelength thick, but in a coaxial cable, for instance, it can be as narrow as you like. 1 Hz signals have a wavelength of 300,000 km but can travel in coaxial cable in a channel 0.3 mm thick, or less.
Hi Malcolm. Thanks for the informative answer. If you have any article about wave properties especially in radio frequency at 27.12 MHz, can you give a copy of it? Thanks
If you are working at 27 MHz then this is referred to as HF and you won't be focussing it or using waveguide or horns.
The wavelength is about 10 m and the antenna is probably a dipole or monopole on ground. These antennas have an aperture about a square wavelength divided by four pi, so look about half a wavelength high and one radian (one sixth of a wavelength) wide. This is the effective aperture. The exact formula is (gain times square wavelength) over (4 pi).
[Actually the antenna intercepts radiation from twice this area, but re-radiates half of it.]
Even if your antenna is very small, if you can make it efficient (by resonating its high reactive component and/or building a feed circuit that can cope with its very high or very low radiation impedance), then it will still have a gain close to 1 and capture power from the same effective area from a passing plane wave - even if it isn't efficient it may still capture the same amount of power, but turn most of it to heat in the antenna and the matching circuit.
Antennas that receive efficiently will transmit efficiently, but at HF efficient reception is not always needed because the noise picked up may be bigger than the signal an efficient antenna could pick up, so an efficient antenna may be wasted. Efficient transmission is always a target - especially when noise may be high; and also a transmission antenna that can cope with high power (which a receiver doesn't have to).
The frequency doesn't affect the behaviour of waves in air - only the scale of them, and the engineering that is used. Try reading books on electromagnetics or antenna theory, like Balanis, or look up HF antennas. If your antenna is not at least 2 m across then it is an electrically small antenna (at 27 MHz) and you need to pay attention to the stuff I said about matching and read a book on (electrically) small antennas.
Maybe it might help to understand that wavelength is not a measure of a physical property of any particular frequency but a characteristic of the physics of the energy wave, a measure of the distance between two peaks of current that are developed as a result of its existence. Waves don't have weight, mass nor thickness to speak of. The thickness of a wave is a concept that simply doesn't apply to the energy form in common understanding and conversation on the subject.
David! Be careful. Don't say: the electromagnetic waves don't have weight, mass. Photons have no rest mass. But where do you see the still photons?
It is widely known and accepted that the EM field, more precisely its elementary excitation, is massless in the absence of interaction with charges. This quantifies my earlier statement. Generally speaking, when having casual conversations among laymen, wave theory is considered to be massless and no physical construct such as thickness.
A wave is characterized by a wavelength, frequency and phase velocity. At the given frequency the wavelength in space is lambda= c/ f where c is the speed of light in space and f is the frequency. lambda= 3x10^8 m/ 27.12 MHz= approximately 10m as calculated before.
I think Mr. Ronald searches for the skin depth of the waves in metals as he wants to shield rf radiation at such frequencies. I followed some previous posts from him where he has some interference from an rf source on his infrared camera.
Shortly the skin depth of an electromagnetic wave in a metal can be expressed by : delta= 1/ sqroot ( pi sigma mu f) where sigma is the conductivity, mu the magnetic permeability and f is the frequency of the wave. For copper it amounts to 2 micrometer at one GHz. At the given frequency it will be about 12 micrometer.
One has to take into consideration that the field intensity of the wave decreases by 1/e of its value at the surface. To let wave decrease to a negligible level one has to make the metal thickness many times greater than delta. This is the case for strong radiation.
For more information please follow the link: https://en.wikipedia.org/wiki/Penetration_depth and the link: https://www.edn.com/electronics-blogs/all-aboard-/4426470/Rule-of-Thumb--4--Skin-depth-of-copper
Best wishes
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