Understanding Antenna Functionality: Comprehensive Explanation Beyond Wikipedia

Question

Hello. Can someone explain to me how the antenna works? the definition on wikipedia is very poor.

bombaatomowa2 · Answer

THESE are the details I wanted to know so vaguely.

scalok · Answer

Well, maybe this:

bombaatomowa2 · Answer

Once I read that a current of a certain frequency fed to the transmitting antenna creates a magnetic field in that antenna of the same frequency as that current had. This magnetic field "wanders" in space hits the receiving antenna and generates a current in it. I just understood that, but I have a dilemma.

On Wikipedia he writes that: Antenna - a device that converts electromagnetic waves into an electrical signal and vice versa.

But the electromagnetic wave is the result of two magnetic and electric fields.
This is how the transmitting antenna sends two electric and magnetic fields (i.e. electromagnetic waves) and the receiving antenna only receives the magnetic field (it ignores the electric field) and from this magnetic field it produces an electric field inside itself, i.e. a flow of current.

In the sense that I don't know if it is like that.

It's nice if someone would describe this action with their own words.

jarek_lnx · Answer

In general, these topics are not simple, you will not find anyone so patient on the forum to explain it to you.

A simple explanation of how the antenna works without unnecessary math - 7 pages:
Link
Can you imagine shortening this to two sentences?

The simplest (intuitive) explanation of EM wave propagation I've seen - 4 pages:
Link

Quote:

This is how the transmitting antenna sends two electric and magnetic fields (i.e. electromagnetic waves) and the receiving antenna only receives the magnetic field (it ignores the electric field) and from this magnetic field it produces an electric field inside itself, i.e. a flow of current.

This is not the case, and the electric field is not the same as the flow of current, what you ask depends on the type of antenna and its dimensions in relation to the wavelength.

bombaatomowa2 · Answer

I called it wrong, I meant that the electric field is a force that forces the current to flow in a closed circuit, i.e. an electric voltage. ============= I understand the topic is not simple. I read a little about the electromagnetic wave. I am only interested in what the antenna transmits and receives because, as I said somewhere, I read somewhere that the transmitting and receiving antenna system is something similar to a transformer, i.e. an alternating current flows in the transmitting antenna which induces an alternating magnetic field and this magnetic field, reaching the receiving antenna, arouses in it the current that runs to the receiver. It wrote somewhere, I do not know if it is good but it seems logical. The sense is that when you read about an electromagnetic wave, such a wave has two components, electric and magnetic fields. And now the question is whether the transmitting antenna only transmits the magnetic field and the receiving antenna receives this magnetic field. It does not need arguments, only in simple words what is happening in such a transmitting / receiving system. And only that, regardless of the antenna structure, because each antenna has the same basic principle of operation, and this is what I mean. And any tips are in Polish, please.

jarek_lnx · Answer

Ordinary 1 / 2? dipole produces both a magnetic and electric field, because the current flows (although the circuit looks open) and there is voltage, a short magnetic component dipole will produce little, just as a small loop antenna will produce little electrical component. But at a great distance from the antenna it will even out because the magnetic component produces the electrical one, and vice versa. We are not a nation of engineers or scientists, so that something is in Polish, someone has to translate it first, go to the bookstore, take a book about antennas and try to read, and in English - there are those that you would be able to understand. You will not find something like I linked - when the EM wave propagates in Polish.

bombaatomowa2 · Answer

Provide some drawings of these dipoles, because there are a lot of them and I do not know which one you mean ipole.JPG You are using different dipole names than in this link. what is this ?? this is the first time I hear of such a thing. And what does such an antenna produce only an electric component? +++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++ I still do not know what the receiving antenna receives a magnetic or electric field?

_jta_ · Answer

There are antennas sensitive to an electric field, to a magnetic field, and to both, depending on the design. An ordinary dipole from the conductor picks up the electric field, and the coil mainly receives the magnetic field. The emission of an electromagnetic wave can be interpreted as follows: the electric and magnetic field resulting from the electric charge (or from the magnetic moment - magnetic charges as yet not detected) adjusts to the position of this charge as it would if it moved rectilinearly from the time when information about its movement may have arrived (assuming that information travels at the speed of light) - this causes changes in this field if the load changes the speed of movement and information arrives that it should be somewhere else - and these changes are just a wave electromagnetic. But there is also an interesting fact: the formula for the energy of the electromagnetic wave emitted by a moving charge was derived, which shows that if the charge in its reference frame has a constant acceleration (theoretically it is possible, at least such a charge will not reach the speed of light), then it does not emit any energy - only a variation in acceleration causes the emission of energy. However, if we are interested in the electromagnetic wave field of a moving charge, this formula does not give it - and according to the one given by the field, it is proportional to the acceleration of the charge.

bombaatomowa2 · Answer

It was supposed to be simple and you are giving me some kind of terrible lecture and you do not understand it.

jarek_lnx help and answer my questions.

Quote:
from Wikipedia
Antenna - a device that converts electromagnetic waves into an electrical signal and vice versa.

The electrical signal is the current generated in the receiving antenna.

_jta_ wrote:
There are antennas "sensitive" to an electric field, to a magnetic field, and to both, depending on the design. An ordinary dipole from the conductor picks up the electric field, and the coil mainly receives the magnetic field.

As you know, an alternating magnetic field generates an alternating electric field, and an alternating electric field generates an alternating magnetic field.

So how the dipole receives the electric field, how it generates the current in the antenna,
since the current is produced by an alternating magnetic field.
==========================================
I still have some confusion about transmitting and receiving what it actually is.

gwas27 · Answer

The antenna is a series LC resonant circuit only open, the point is that as much RF energy as possible. was radiated into space and not concentrated in the L and C elements as on the electronic board, in addition, the resonant circuit is tuned to the frequency at which it is to work - the antenna is tuned to the frequency at which it is to work

bombaatomowa2 · Answer

Correct the beginning. ANTENNAS, what are the antennas or the antenna ?? Moreover, you are going into advanced details and not what I mean ?? How the antenna is open circuit ???

gwas27 · Answer

It is as if you have stretched the coil and it has no more turns but has inductance

Added after 7 [minutes]:

Antenna sends RF signal , the signal goes some distance and returns to the ground of the antenna, in CB antennas the antenna is a radiator with a coil at the base and the antenna is counterweighted, i.e. the car body is the mass

Added after 3 [minutes]:

In CB handheld radios the antenna is smaller and the counterweight is smaller and the transmission range is also smaller, although CB handheld and car radios have the same power after 4W

bombaatomowa2 · Answer

I guess you still don't know what I mean. You are going into very advanced details. I ask for an antenna in general, but I do not specify a specific type.

A pathological explanation, the transmitting antenna produces electromagnetic waves and the receiving antenna receives this wave. Everything is okay, you can say a humanist and it is enough for him. I want a little more, but only a little.

=====

As I said before, alternating electric fields generate alternating magnetic fields and vice versa. I remember that from school

The transmitting antenna receives a current / signal with specific parameters, forced by the voltage, i.e. the electric field, this current creates a magnetic field in the transmitting antenna that goes in a specific direction in space, the magnetic field in space creates an electric field and we have electromagnetic waves. This electromagnetic wave reaches the receiving antenna and the magnetic field from the electromagnetic wave induces an electric field in the receiving antenna which forces the current in the receiving antenna to flow to the receiver. So the electric field from the electromagnetic wave is only the field "accompanying" the electromagnetic field in space and it is "ignored" by the receiving antenna.

Means summarizing briefly, the transmitting antenna produces a magnetic field which is then received by the receiving antenna, and the electric field from the electromagnetic wave is only a component of this electromagnetic wave which this component originates from the magnetic field of the transmitting antenna, and it must be because this is the nature of the waves.

I understand it like that and I ask YOU if you understand correctly? I am always following this rule from school (bold). And that's how I imagine it. If there is an error somewhere, please correct my text in red and send it in a message. If it's good, that's enough for me.

jarek_lnx · Answer

Because what else do I mean, let's assume that I am talking about a simple dipole, two currents from a wire and a HF voltage source connected in the middle. let's assume that it is a resonant antenna with a length of 1 / 2? for high frequencies these two rods have a significant inductance but they have capacitance, you can smooth out the current and voltage distribution in a half-wave dipole, the current flows, there is voltage, this creates a field magnetic and electric and it will react to both components in the same way. In (old) movies you probably saw them driving a car and on the roof they have a loop that they spin in search of the direction of the strongest signal The first time you hear it, you don't have to tell me, I can give you a few more random antenna names and you will say the same. Such an antenna is a large coil, you could say that it reacts and produces only a magnetic field, but this is not true, unless we are talking about a small loop, e.g. 1 / 10? in diameter, in turn, a short dipole again let's assume that 1 / 10? generates mainly an electric field, although small the antennas would fit your imagination, they are rarely used because they have poor efficiency. There is no right answer to a wrongly asked question. The answer is it depends on the type of antenna, but usually both. The circuit is not open, only there are no inductances and capacitances concentrated in it.

_jta_ · Answer

Let's take a dipole antenna and connect a DC voltage to it - it will create some electric field around itself. This field will have some sort of arrangement in space. If instead of DC voltage it will be variable, but slowly changing - the field will also be variable and its system will be almost the same (at least it will not be possible to detect the difference). But if the voltage changes faster, the changes in the electric field will lag behind the changes in voltage - the field energy at a greater distance will not have time to return before the voltage changes sign - and when it changes, the dipole will not accept this energy anymore, it will be sent as electromagnetic wave. This is more or less the explanation of how the antenna works in a popular science book half a century ago. The intermediate distance - not so close that the field changes to the voltage changes, but not so far that the field is considered a wave, is taken as ? / 2?, where ? = c / f is the wavelength. A decent antenna should have a large fraction of the field energy at distances greater than this intermediate distance.

Aha - in a resonant circuit from clustered elements, energy is collected by a change in the electric (capacitor) and magnetic (coil) fields; in an electromagnetic wave, both fields "go hand in hand", ie in the same place there is an arrow (the highest intensity) of both fields (the drawing of two intertwining fields, found in popular books, and maybe sometimes in school textbooks, is wrong). This means that the elementary antenna is either electric or magnetic (only one of the fields in the wave is in phase with the same field at the antenna itself, the other is out of phase - for example, it has zero in the wave when it is the largest in the antenna). If the wave reflects from a perpendicular surface, a standing wave is created - in it there are "intertwined" fields and arrows of one field correspond to the nodes of the other, and both fields appear alternately - there we notice the difference in the operation of the electric and magnetic antenna, because, for example, an electric antenna node (zero) of the electric field will perceive nothing.

bombaatomowa2 · Answer

AND)

What I drew above is this, I understand from what you tell me about a simple dipole.
We supply power to the dipole and since the dipole is interrupted, the current does not flow and an electric field arises around the dipole. So an antenna with a straight (broken) dipole is an electrical antenna.
Okay??
===============
B)
And I understand well that the loop dipole creates a magnetic field because current flows through it, so a magnetic field must be created. So an antenna made of a loop dipole is a magnetic antenna.
Okay???
=======================
C)
But it doesn't understand one thing if an electric transmitting antenna is transmitting an electric field, how does an electric receiving antenna react to this field ??
As I said, a variable electric field produces an alternating magnetic field and a variable magnetic electric variable, so the receiving antenna must react to the magnetic field in order to create an alternating electric field inside which is responsible for the generation of the current.
Anyone else explain this to me?

_jta_ · Answer

The electric field leaves the dipole and enters it - not like in the picture, where the line at the top has a right-hand arrow and a left-handed arrow at the bottom.

A) Yes, it is an electric antenna.

B) Good.

C) The "straight dipole" antenna reacts to the electric field - the current flows because the dipole bars are being charged.

gwas27 · Answer

Is it possible to calculate the antenna or simulate its operation on a computer, can it be done?

_jta_ · Answer

It is possible and it has been done a long time ago - see if there are any leads on Wikipedia.

bombaatomowa2 · Answer

How left-handed? After all, the arrows at the top and bottom point in the same direction. Alternatively, draw as you think. Does not understand. After all, in school they were breaking that in order for electricity to arise, there must be an alternating magnetic field.

_jta_ · Answer

Unfortunately, I do not have how to make a drawing now - but in the figure in # 18 the arrows on the lines contradict each other.

After all, at school they cracked that in order to generate electricity, there must be an alternating magnetic field.
That there is a current in a coil connected to a closed circuit. And in the open, it is created in an alternating electric field.
If you put an electric dipole in a node of a magnetic field, you get a current like in an electric node - no.

bombaatomowa2 · Answer

You don't understand what you mean with these arrows. Draw and show in the lady. Let's say to the left is the pole N, to the right is S, and the arrows are from N to S and the bottom and top of the picture. Explain it more clearly.

_jta_ · Answer

You don't understand what you mean with these arrows. Draw in the lady I won't draw, I don't have time. Imagine a clock whose hand moves towards the larger hours (i.e. like a regular clock) when it is at the top of the dial, and towards smaller hours (i.e. opposite to the normal clock) when it is at the bottom of the dial - something like this. this is in your drawing. Explain it more clearly. Write (1) what you don't understand and (2) what terms you understand correctly - as it was in the school textbook. The forum is not a substitute for learning at school, because for this you would have to rewrite half a textbook.

bombaatomowa2 · Answer

AND. After all, the arrows have the same point of view. I don't understand what you mean. ================================================== ========= B. There was nothing about antennas at school in physics. And now it interested me. I still cannot imagine that a current could be generated under the influence of an external electric field. They always explained at school that the current in the coil was created from an alternating magnetic field, and here you say that it is also from an electric one, but how? The electric field is the field between the oppositely charged poles, then the molecules interact with each other by attraction or electric field, and the difference between the charges is the voltage. So the stronger the field, the greater the tension. ================================================== ============ C. Is the signal strength different from the wave amplitude ?? (at least that's how I understand it) ================================================== ============ D. Antenna from this link, one of the criteria for dividing antennas is: Due to the coupling with the component of the electromagnetic field: - electric antenna (e.g. dipole antenna) - magnetic antenna (e.g. ferrite antenna) And now, if I go to the reference to the dipole antenna, it shows me again the division of dipole antennas into given types, for example: Simple dipole (a) Loop dipole (b) e.t.c. In this situation, I do not understand why earlier (post # 19) you told me that a loop dipole antenna is a magnetic antenna and a simple dipole is an electric antenna, since on wikipedia they write that both types are electric antennas. Now again, I don't know when the antenna is electric and when magnetic (i.e. what does it depend on structurally? ========== E. I would like to ask one more question regarding the satellite dish. It is known that the satellite dish reflects the signal from the plate and focuses it to the fire where the converter is. I wonder what does this focusing the signal in one place give? In addition, when we increase the antenna, it will receive more, reflect and will focus this signal. It doesn't understand that the more the signal will focus the better? What happens when the signal is concentrated in one place? I know that the directors in the directional antenna create their own fields and how these fields overlap there is wave interference, so the wave amplitude increases, and therefore the signal strength. But in such an antenna there is no focusing the signal to a certain point as in a satellite dish. And that's why he doesn't understand what this focusing of the signal gives -------------- REQUEST It is important to me to understand this in this fundamental point that is being discussed here. I am counting on your understanding.

_jta_ · Answer

A - If you follow the drawn lines as shown by the arrow, you will hit the arrow in the opposite direction - it shouldn't be like that.

B - If you have electric field lines that enter a conductor and the field is changing, then a current is flowing. This is mainly used in capacitors.

C - Rather, the power transmitted (emitted or received by the antenna) and is often expressed in dBm - logarithmic unit of power.

D - The circular loop is a magnetic dipole; a loop in which two wires run close to each other, at the ends are connected, one of them is interrupted in the middle and there is a cable connected to the receiver / transmitter, it is an electric dipole - these are two electric dipoles next to each other acting as a 4-fold step-up transformer antenna impedance.

E - 1. When the signal is focused, the field is stronger, the signal strength is greater - without focusing, the power would be too low for good reception. 2. Focusing works for a specific direction - the antenna will pick up signals from that direction, not interference from other directions. 3. Directors also focus the signal - on the principle of wave deflection.

bombaatomowa2 · Answer

But I was the one who drew the field arrows at any given moment in time. You know when the field changes, the arrows will be in the other direction. It is like a magnet, when you sprinkle it with filings, they are arranged along the field line between the poles. -------------------------------------------------- ---------------------------- The alternating magnetic field creates an alternating electric field inside the conductor, and if the conductor is closed, current flows. If the electric field itself enters the conductor, electricity will also flow and this is what happens in the antennas. Get it right ?? -------------------------------------------------- --------------------------- The term Signal Strength, which is named in receivers, is a misnomer in everyday speech, and one should expertly say Signal Strength. Get it right ?? -------------------------------------------------- --------------------------- Please write it in Polish because you have set commas, semicolons and you don't know what it refers to. -------------------------------------------------- --------------------------- So the distance range depends on the focus of the signal. Having two antennas, one omnidirectional, the other directional and transmit the signal with the same power, is the distance range of the transmitting directional antenna greater than the omnidirectional antenna? ===== Focusing the signal is something similar to bringing two magnet bars together. if the magnets are quite close to each other, the field (or signal) is stronger and when we spread the bars, the field is weaker. Got it well ??

_jta_ · Answer

A - And you drew the field lines wrong - for the dipole antenna the electric field lines go into the conductor, see it in Wikipedia.

B - A rough approximation.

C - The signal strength is quite commonly used, for example in amateur radio.

D - See Folded dipoles - it is electric, and Loop antenna - it is magnetic.

E - Yes, the directional antenna has a greater range in "its" direction than the omnidirectional one.

bombaatomowa2 · Answer

Where in Wikipedia? But should it be signal strength correctly ?? You entered in English. Correct what I said before and it will probably be ok. It means that there is a mistake on Wikipedia: saying that all dipole antennas are electric antennas ?? ==== And with this focusing of the signal, which I compared to the approach of a magnet, do I understand it well?

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