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-1
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2answers
27 views

Skywave Radio Propagation [closed]

What physical laws govern the reflection and propagation of radio waves off of the ionosphere? I am trying to locate papers, journals or experiments that have been devoted to studying this phenomenon....
0
votes
1answer
30 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 ...
0
votes
0answers
49 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? ...
0
votes
1answer
23 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 ...
1
vote
2answers
51 views

Will the thickness of a material affect the reflection properties

Does a thicker piece of material(lets say metal) reflect wifi signals the same as a thinner piece of material? I realise that thicker materials would block out more at the back, but my question is ...
1
vote
0answers
19 views

Does mobile phone user density in an area affect signal reception? [closed]

Whenever I go to a very crowded area (like during New Year celebration), where a lot of people gather in a space, usually my phone's data connection becomes very bad and even stopped working. Even the ...
0
votes
0answers
20 views

Range of radio communication on a flat world

Suppose you have a flat world with gravity, atmosphere et cetera similar to Earth, that's either infinitely large, or large compared to the relevant scale here. What would be the effective range of ...
2
votes
1answer
32 views

How to make radio transmitter and reciver [closed]

I want to make a simple but useful radio transmitter and reciver.I dont know which one is better, Fm or Am or other types? Just want it to send pulses like morse code not complicated voice or other ...
1
vote
1answer
66 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 ...
1
vote
0answers
29 views

Baby monitor has more static when toilet is flushed? [closed]

I have a baby monitor in the basement of my house, and it's picking up the signal of the microphone transmitter on the second floor. It's not a great quality monitor, so there's always a small amount ...
1
vote
2answers
79 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
1answer
33 views

Effectiveness of Layered EM wave shields [closed]

Which is best at shielding EM waves; a Faraday cage with sides made of blocks of metal, or layers of metal (with insulation ie plastic & without), or is there no difference between the three? &...
0
votes
1answer
58 views

Electromagnetic Shielding of radio waves

Would a radio wave beam (perhaps a cm in diameter) with the same frequency as ordinary AM or FM radio waves and also the same voltage (v/m) have the same skin depth for any metal utilised to shield ...
0
votes
2answers
79 views

Can we determine the location of a radio station if we know the wavelength and frequency of radio wave emitted by that radio station?

let say that we can detect the wavelength and frequency of radio wave then can we detect that from where these radio waves are coming or from how much distance these waves are coming?
0
votes
1answer
54 views

EM Wave shielding of different frequencies

Is more aluminium required in Faraday cages to block AM or MW radio waves compared to FM frequencies (of equal power)? If yes, is this difference directly proportional to the decrease in frequency (FM ...
-1
votes
1answer
178 views

What is the underlying physics that makes Li-Fi “100 times faster” than Wi-Fi? [closed]

Consider this webpage, which compares how the two work. Particularly it says (and I'm paraphrasing) that Lifi transmits using light from LED bulbs and WiFi uses radio waves. Well, both are EMF waves, ...
0
votes
2answers
113 views

How exactly do radio waves work?

So I understand that a radio wave is created by electrons oscillating in the antenna. But how does this create a radio wave? How are the electric and magnetic field "emitted" by the electrons? If you ...
1
vote
3answers
115 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 ...
-4
votes
1answer
30 views

Limitations of radiowave speed [closed]

If radio waves travel as fast as light, how was nixon able to talk to the apollo moon crew in real-time over a phone? it seems this concept makes the idea of seeing something billions of light years ...
1
vote
0answers
71 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
2answers
78 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 ...
3
votes
1answer
80 views

Why can't we see better with an antenna?

Or alternatively: Why don't antennas look like telescopes? If visible light and radio transmissions are the same thing, why is there such a difference in the equipment we use for augmenting it?
75
votes
4answers
13k views

Can tin foil hats block anything?

This is joked about all the time, but... Can tin foil hats actually block anything? If they can, what frequencies? Is there any research into tin or aluminum foil and radio blocking or amplifying ...
0
votes
1answer
101 views

Am I absorbing radio waves?

I have bluetooth speaker that I can control (via bluetooth) with my phone. One day I happened to roll on top of my phone with my chest and the music stopped playing (until I rolled off of it and it ...
0
votes
2answers
45 views

Does observing an EM wave take energy from it?

Here is the question that got be started on this: Suppose 1,000 people were sitting in a room with their laptops out and a WiFi transmitter in the front of the room. If everyone was connected to the ...
0
votes
1answer
97 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?
0
votes
1answer
83 views

Why does radio sometimes oscillate in and off tune while driving a car

Sometimes while listening to radio on a car I notice the tuning will periodically go off tune (you hear just noise) and back in. Apparently it depends on the car's position, i.e. if I stop on a "in ...
8
votes
1answer
195 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
2answers
122 views

Is neutrino-based communication possible?

Referring to this article, where we see there are three flavors of neutrinos, got me thinking of simple binary-based communication, but more like the UDP protocol where we can live with dropped ...
0
votes
0answers
29 views

Does RF have any non-orthagonal properties?

Quantum Key Exchange takes advantage of the fact that observing a photons polarization will alter it's polarization. This, along with some tricky back and forth, allows two people to exchange data ...
2
votes
0answers
35 views

What are the fundamental limits of very tiny radios?

For a hard SF story, I'm wondering about the physical limits of communications devices in a micro robot, say, the size of a mosquito. Figure one microgram mass. Real rechnology has already come a ...
2
votes
2answers
329 views

If the ionosphere reflects radio waves then why use satellites? [closed]

Please explain the main physical advantages of using satellites for communication as I'm sure there are many.
1
vote
0answers
71 views

Can an open cup attenuate radio waves as well as a Faraday cage?

The problem is that thieves in my neighborhood are using a power amplifier to increase the "bubble distance" of my car so that it thinks that my key fob, which is sitting in my house, is next to the ...
0
votes
2answers
108 views

Why can't LIDAR be implemented with traditional antennae?

In robotics, LIDAR and RADAR are both used for obstacle detection. The data they produce are very similar, but they do have different qualities (LIDAR is more precise but less robust). There are many ...
13
votes
3answers
2k views

Where does background noise go on a radio station?

If you tune a radio to a frequency where there is no station broadcasting, you hear noise. It's pretty loud, just as loud as the music that comes in when you find a station. And yet, when you do ...
0
votes
0answers
103 views

What have we built? A resonant loop antenna? Rhombic?

Some background, my partner and I have built an antenna we are supposed to characterize for an assignment, and compare it to physical predictions. However, we don't know what type of antenna we have ...
1
vote
2answers
268 views

Does a source emitting visible light also emit infrared, microwave and radio waves?

I have a bulb which is hot enough to emit visible light and obviously it's hot enough to emit radiation which lies before the visible light temperature i.e. radio waves, microwaves, and infrared light....
1
vote
2answers
242 views

Do Sidebands mean the frequency of an AM radio wave is not constant?

I'm studying for A-level now..... I have read some other posts explaining how the sidebands generated after the carrier wave is modulated. So, if there is sideband frequency, the frequency isn't ...
2
votes
4answers
1k views

Does the information transfer in the internet also work with waves like radio and TV do?

I am accessing the Internet, downloading PDFs, and much more, but how? The servers are far away, but how do I download data if it is far from my computer? I can watch football matches live on ...
1
vote
1answer
85 views

If there were intelligent life in another galaxy, would we notice? [closed]

I've read that once intelligent life successfully achieves interstellar travel, it could populate the galaxy in tens of millions of years, likely populating the most habitable planets and preventing ...
0
votes
1answer
79 views

How to use radio waves to calculate distance over short distances?

I read an article about a company that created the equivalent of a GPS location system for internal spaces where the satellite based GPS is blocked. They made reference to the Fresnel number as to ...
0
votes
0answers
66 views

Extremely long wavelength electromagnetic radiation

High frequencies are used to eject electrons, because only electrons can really be affected at such a small wavelength scale. But could an electromagnetic wave have such a ridiculously low frequency (...
0
votes
0answers
28 views

paramagnets with high magnetic susceptibility

i'm thinking of using paramagnets as cores for receiving antennas, same as ferrite rods are used as the core for AM radio antennas. why paramagnets? a material that can demagnetize itself after being ...
1
vote
1answer
344 views

Why are there dead zones near an antenna using the sky-wave propagation system?

I have heard in my class that there are dead zones near the antennas which use the sky-wave propagation system. I have also been told that cell phones are unable to receive signal near the antennas. ...
3
votes
1answer
182 views

Electromagnetic radiation bending on Earth

Most articles say that a radiowave is able to propagate itself beyond the horizon because it is reflected off by the ionosphere (and the Earth itself). But do radio waves also get bent according to ...
1
vote
3answers
197 views

Plane waves - EM wave

An accelerating electric charge will emit transverse electromagnetic waves. These waves are propagating away in wave fronts that become flatter and flatter as getting further from the source. So they ...
3
votes
5answers
585 views

If an antenna must be $\frac{1}{4}$ of the wavelength, how can car antennas be so small?

If the transmission antenna has to be $\frac{1}{4}$ of the wavelength, how can the car antennas' size be much less than that and properly receive the radio signal?
1
vote
1answer
64 views

Finding the direction of several radio beacons using a faraday cage and a radio receiver

I'm trying to build a system that can detect the direction of a set of radio beacons operating on the same frequency. In order to do this I have planned to use a normal radio antenna placed inside a ...
1
vote
2answers
521 views

Is data which rides on the carrier frequency dangerous?

My understanding of broadcasting data via electromagnetic radition is, that the data "rides" on a carrier frequency on which it is radiated. I am aware of the fact, that those carrier frequencies are ...
0
votes
0answers
75 views

Radio telescope alternative. Does a high resolution radio camera exists?

I'm looking for an alternative to a radio telescope. Does a high resolution radio camera exists?