Questions tagged [antennas]
The interfaces between radio waves propagating through space and electric currents moving in metal conductors, used with a transmitter or receiver. Antennas are essential components of all radio equipment.
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Can Stern-Gerlach spin alignment be seen as a result of EM radiation of precessing magnetic dipole?
Stern-Gerlach experiment is often seen as idealization of measurement. Using strong magnetic field, it makes magnetic dipoles (of e.g. atoms) align in parallel or anti-parallel way. Additionally, ...
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Can we catch signals from a cellphone using an external device? [closed]
What if someone stole em waves from our mobile devices to listen to our conversations or get our OTP. Whatever encryptions they have they are just EM waves innit and they cannot be propagated only in ...
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Dipole antennas and the $B$ field
A dipole antenna responds to the electric component of a EM wave. Does the magnetic component of a EM wave have any effect on the performance of a receiving dipole antenna?
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Why does the length of an antenna matter when electromagnetic waves propagate perpendicular to the antenna?
The optimum length for a dipole antenna is a multiple of half the wavelength that it is designed to receive or emit. Why is this? If an electromagnetic wave has E in the x-axis, B in the y-axis, and ...
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Magnetic object affected by electromagnetic wave
If a dipole antenna is strong enough, can it make a compass needle oscillate?
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How many photons are received per bit transmitted from Voyager 1?
As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons ...
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Polarization Derivation
Can how I can find the phi and theta unit vectors as described (Eq. 4a and 4b) in the following paper on antenna cross polarization? I thought the thetha and phi unit vectors were the same as those of ...
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How do antennas work?
I know the basics about em radiation. However, I’m not in college, and I’m not a genius. I’m really looking for someone that’s willing to help explain this to me in a relatively simple way, without ...
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How does the human body affect radio reception?
My sister asked me why her small radio sometimes has better reception when she places her hand nearby (without touching) the antenna. I did some research and wanted to ask a few questions.
Here are ...
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Electromagnetic field of dipole antenna
Why do dipole antennas generate EM waves by alternating electric fields instead of alternating magnetic fields?
Why don't alternating magnetic poles detach the magnetic field like how it can do so ...
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Difference between directional and omnidirectional transmission or reception?
It is suggested that the next generation wireless technology will be highly directional since this increases the signal gain (MIMO) and decreases interference.
How will the receiver still be able to ...
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Minimum frequency for a dipole antenna to work
Does a dipole antenna need a minimum frequency of AC to make the electric field detach and propagate?
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Radiation efficiency of patch antenna
The figure 2.54 is taken from the textbook Jean-Marc Laheurte, Christian Ripoll, Dominique Paret, Christophe Loussert, “UHF RFID Technologies for Identification and Traceability”, 2014, John Wiley &...
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Why electromagnetic radiation happens more effectively at high frequencies?
Why is the amount of power radiated by an oscillating current source much smaller at lower frequencies?
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Derivation of the total received field in ground reflection model
I am reading this book by J.D. Parsons.
The problem concerned, is how to find the propagation model for propagation over a curved reflecting surfac, i.e.:
I would like to know where is the ...
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