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5
votes
1answer
142 views

A “figure-8” EM field created by a dipole antenna

This question pertains to the EM field of a Pulse W5017 dipole antenna. The data sheet of this antenna can be found here (which contains information regarding the radiation patterns). There are TWO ...
0
votes
1answer
27 views

Can antennas work with high frequency EM waves?

Antennas usually work with FM waves, and AM waves, which mostly used in telecommunications. Information is transferred on FM, and AM waves by a transmitter transmitting information on these EM waves. ...
0
votes
0answers
10 views

How can I determine if A 34 meter antenna can be used as PTA?

What are the general requirements for any antenna, e.g., one with 34 m of dish, to be used as PTA (Pulsar Timing Array) monitoring? What are the main formulae to be used? How can the TOA (time of ...
1
vote
2answers
370 views

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 ...
0
votes
0answers
26 views

Antenna measurements and parameters calculation

Lets suppose we have some data collected from antenna measurement. For every theta and phi point in any coordinate system ( here refering to Ludiwg coordinate systems II and III) the data can be ...
0
votes
2answers
35 views

Transmission Lines and Antennas

In Transmission Lines, does the electric field exist between the two conducting wires or does it exist inside a wire, pushing the flow of electrons? And do all antennas radiate energy by spark?
1
vote
0answers
22 views

Impact of antenna spacing larger than a half of wavelngth

I am building a uniform linear antenna array (ULA) of Wi-Fi to extract channel state information, or channel matrix $H$. With some literature search, as not familiar with antennas and electromagnetic ...
3
votes
1answer
44 views

Antennas and the electromagnetic field

I'm an electrical engineering undergrad and have some questions about radio antennas. We've just covered the electronics and maths of radio theory once the signal has reached the receiver, I'm ...
1
vote
1answer
64 views

A Formula for the Phase Difference Between the Electric and Magnetic Wave Oscillations?

A) Is there a formula for the phase difference between the electric and magnetic field oscillations, in vacuum, in an electromagnetic wave emitted from an antenna, as a function of the frequency the ...
0
votes
0answers
15 views

Directivity of dipole antennas inconsistency

I'm trying to model the directivity of dipole antennas of differing lengths. There are two main ways I've thought to approach this. The predicted radiation pattern is given by $$P_{\mathrm{predicted}...
0
votes
1answer
31 views

Recommended reading about antennas? [closed]

I am trying to learn a bit about antenna theory in order to understand how Nikola Tesla may have misunderstood them. (Thank you CuriousOne for your response to my earlier question! It was helpful in ...
7
votes
1answer
5k views

Adverse Health Effects of Strong Radio Waves

A while ago, I was hiking near the Hollywood Sign in Los Angeles. When I got to the sign, I found out it was fenced off; with several signs and a security camera promising prompt enforcement. As I was ...
0
votes
0answers
50 views

Why is the satellite dish still needed?

How much does it amplify the signal? The receiver cannot pick up the signal without the dish? Is it possible that it will disappear in 10 years? As the sensitivity of the receiver is enhanced? ...
7
votes
0answers
94 views

Why is it that fractal antennas can filter out so many frequencies?

As known, fractal antennas are used for example in cell phones. But why is it that so many different kinds of frequencies can be filtered out of the forest of radio waves surrounding us? Is it because ...
0
votes
1answer
26 views

Why should we extend the radio antenna to make it work though we board on enough height? [closed]

The old FM radios have an antenna to receive radio frequencies and work on them. If I am in ground floor, I have to extend or spread the antenna to make the radio work. Now if I go to the first or ...
14
votes
2answers
2k views

How do you make a spherical radio wave?

A vertical rod, a usual dipole, produces radio waves in the horizontal plane, mostly in two opposite directions: If that is possible, how do you produce a spherical EM radiation? should the ...
1
vote
1answer
73 views

Why doesn't a transmission line mess up an antenna resonance?

I don't understand why the resonance of an antenna is not affected by the transmission line to the receiver. For example, given a dipole antenna like the following: The antenna length is carefully ...
0
votes
0answers
21 views

How much energy would be required to remotely induce a signal in a wired network (e.g. Ethernet)?

How much energy would be required to remotely induce a signal in a wired network, such as Ethernet? Assume, for the sake of discussion, that the wired network has a single cable of length $l$ (eg 10 ...
0
votes
0answers
32 views

Half wave antenna

I need to calculate the magnetic field intensity at a distance $x$ and angle $\theta$ for a half wave dipole antenna. I know the length of the antenna is $$ l = 333.33mm$$ and the magnetic field ...
0
votes
0answers
37 views

Calculating instantaneous field strength for known signal source

I was referred here from electronics stackexchange. Suppose I have a time varying signal source V = Vm cos(wt). This source is fed to a half wave dipole antenna which in turn radiates electromagnetic ...
1
vote
1answer
89 views

Light is/produces a electromagnetic wave, but is the opposite also true?

A similar question has been asked, and to some extent the answer is: you need an antenna with $L \approx 200nm$. But it's not entirely clear to me if this is completely hypothetical, as "Marek" also ...
3
votes
2answers
214 views

How do radio antennas follow electrical rules

Power = current times voltage. However current requires a complete circuit to 'flow'. How can a 1,000 Watt antenna work if the output of the transmitter is connected to a single emitting wire or ...
4
votes
4answers
2k views

Radio waves and frequency of photon

How radio waves create the current in antenna in terms of photons? If it is Compton scattering then why is not changed the freuency of photons?
1
vote
2answers
95 views

Will radio waves bend to reach receiver?

I was wondering if receivers just catch the radio waves that pass through, or if they actually attract the waves like a magnet. In other words, will a radio wave moving in a straight line bend in ...
1
vote
0answers
28 views

Is it possible to make an antenna that's more compact than a split-ring resonator antenna? [closed]

I'm aware that a split-ring resonator antenna works efficiently by being half the size of a classic antenna. But is there any design that takes even less space? I have in mind millimeter or micrometer ...
1
vote
3answers
122 views

How does the tuner really work in a crystal set?

I would like to know how and why the tuner works in a crystal set radio. I already know all the theory and the "formal definitions" (this creates a resonant circuit which responds to an alternating ...
0
votes
0answers
23 views

Radio wave propagation path loss coefficient below 2?

We did a series of measurements of radio wave signal strength. The setup was between stations on top of flat roofs of neighbouring houses (with line of sight). We are interested in the path loss ...
1
vote
1answer
72 views

Dipole antenna $E$-field direction

I was looking up dipole antennas on Wikipedia, among other sites. I came across this animation: and was wondering why there wasn't any field lines in perfectly vertical direction. In the case of a ...
1
vote
2answers
57 views

Do a receiving antenna interfers with an emitting antenna?

As I understand: Accelerating electrons generate electromagnetic waves. An emitting antenna have an alternating current (electrons are moving) which generates an electromagnetic waves. The ...
0
votes
2answers
83 views

There is no reverse flow of energy in a mismatched transmission line, is this correct?

I have already posted this question on the Amateur Radio site, but I would value opinions from a more theoretically based group. Is this text correct? I use it when helping people to study for ...
1
vote
0answers
73 views

How is my guitar cable picking up clear radio-signals?

I've recently noticed radio-signals coming through my guitar amplifier. I'm on the top floor of a building in a densely populated city, with a clear visual path to many other buildings. My guitar ...
0
votes
0answers
31 views

If we had a radio antenna produce visible light? [duplicate]

If we had a radio antenna produce visible light would it degrade the quality of the antenna due to the light production. How fast would be the degradation?
2
votes
2answers
168 views

Rigourous Treatment of Antenna Theory/Physics

As a rising senior who has finished his QM sequence but not yet done an E&M/optics sequence, but is about to start a research project that will be a large part antenna design and optimization, ...
0
votes
0answers
12 views

Getting H-Plane Cut from Near to Far Field Transformation

I am using the Near to Far Field Transformation method described in http://www.keysight.com/owc_discussions/servlet/JiveServlet/download/72-15457-47956-2405/36-tkadlec_roman.pdf. The method describes ...
0
votes
1answer
37 views

Connecting two antennas to provide signal

Problem: I am in a room without FM signal. I would like to provide FM signal to the room. If you have a hole for coaxial cable, which can connect a place with signal and the room, is it possible to ...
0
votes
5answers
253 views

Sequence of E and B field in radio waves and in single photons

In antenna technology we distinguish between nearfield and widefield. In the nearfield the electric and the magnetic fields are shifted by 90°. If you look closer you can see that there are two ...
2
votes
2answers
470 views

What happens to a photon after it is absorbed by an antenna?

I recently have read about interception of wireless information, however this mentions that people can intercept the information, and then somehow the recipient also gets the information. Regardless ...
2
votes
0answers
29 views

How to mathematically model a realistic aperture illumination?

I want to know a mathematical expression that I can use to model a realistic aperture illumination to produce the primary beam of an antenna so that the radial distribution of this aperture ...
0
votes
2answers
70 views

Is a longer antanna better for reception ? Or just more directional?

Let's say I have two antennas, A1 and A2, and they have identical radiation profiles. So the relative radiated energy in a given direction is the same for both antennas. Let's assume also that we ...
0
votes
1answer
98 views

If electromagnetic waves can be generated by oscillation of a coil why can't light? [duplicate]

I was recently reading how electromagnetic waves are generated using oscillation of a current in an antenna. Why is it that this principle cannot be used to generate light?
1
vote
2answers
117 views

Explanation for: A monopole antenna must contain a resistor (or equivalent) and therefore must have 2 terminals?

Could someone explain why this sentence makes sense: A monopole antenna transfers energy from electrical domain to the electromagnetic domain, hence must contain (equivalently) a resistor, hence ...
1
vote
2answers
2k views

What happens when length of antenna >> lambda

Length of a dipole antenna according to antenna theory should be lambda/2 for best reception. I am just curious about the outcome when length of dipole antenna >> lambda. Impedance will be zero in ...
8
votes
1answer
203 views

Why do I hear voices when I touch my turntable needle?

So I was trying to figure out the reason why my old (and probably sufficiently damaged) needle on my phonograph (turntable) was not working like it was a little while ago. With my headphones on, I ...
0
votes
1answer
38 views

Wideband metamaterials in mobile-telecommunications bands

Were there any metamaterials (materials, settings, geometry) studied that are non-resonant (not frequency selective) in the frequencies between 700 MHz and 2700 MHz, therefore useful for mobile ...
1
vote
1answer
38 views

Layer of graphene on reflector of an antenna

First of all I have no idea how well graphene "sticks" to other metals, but let's suppose it does (well, if I may please ask you to reply to the "stick" question too...). Given the material great ...
0
votes
2answers
82 views

Wave frequencies and barrier width?

I know a fact that says a wave can go through barriers thinner than its length. This is why for example FM radio can be picked anywhere while antenna TV needs direct sight to the transmitter. Is this ...
1
vote
0answers
66 views

Why are most antennas in cellular networks +/- 45° polarized?

I've just been asked a strange question that I cannot find an answer to (even on the internet it seems I can't find any explanation for this) and I ended up wondering why most of the antennas which ...
1
vote
0answers
37 views

How to describe frequency spectrum with samples?

I posted this same question in math, but nobody is answering, so I thought I'd give a try here too... To me the question is pretty straightforward, but nevertheless I have to explain its background ...
0
votes
1answer
56 views

$H$ field from corresponding $E$ field (antenna)

The $E$ field at $kr >> 1$ due to a short dipole oriented in the $z$-direction and located at the origin is: $$E_0 = \frac{10^3e^{-jkr}}{r}\sin\theta\space\space(V/m)$$ Can I just solve for the ...
0
votes
1answer
72 views

Effective Area of Isotropic Antenna: Explanation?

I'm reading some introduction to antenna theory and I've often puzzled on the equation: $$ A_{eff} = \frac{\lambda^2}{4\pi} $$ which relates the effective area by which an antenna captures radiation ...