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7
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1answer
104 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
63 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
22 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
25 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 ...
3
votes
2answers
78 views

If the ionosphere reflects radio waves then why use satellites?

Please explain the main physical advantages of using satellites for communication as I'm sure there are many.
1
vote
0answers
29 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
84 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
1k 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
17 views

Dipoles lengths underwater vs on land

A submarine (for example) uses a VLF communications system to remain in contact with its headquarters while submerged. The submarine drags a resonant dipole wire antenna behind it in the water. The ...
0
votes
0answers
49 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
123 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 ...
0
votes
1answer
95 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
331 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
75 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
52 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
51 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
26 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 ...
0
votes
1answer
149 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
94 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
153 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 ...
2
votes
5answers
192 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
34 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
498 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
61 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?
4
votes
2answers
97 views

How does a fixed amount of transmitted radio energy supply an unknown number of destinations?

I did some maths and physics up to the age of 18, and hold an amateur radio licence. This thing has puzzled me for a while - does reception of an electromagnetic wave imply an interaction with the ...
3
votes
2answers
156 views

How are electromagnetic waves differentiated?

I would like to know how the signals for remote controlled cars, radios, etc.. That use radio waves are told apart from each other. I know that the radio waves are modulated to encode data and the ...
3
votes
2answers
2k views

Why is bandwidth, range of frequencies, important when sending wave signals, such as in radio?

So in wired/wireless networking and radio, signals are sent in form of wave. Then the concept of bandwidth comes in, which is the difference between highest frequency and lowest frequency in a signal. ...
4
votes
1answer
142 views

AM Receiver and sideband frequencies

How sorry for "dummy" question. I have difficulty to understand how the AM receiver. Being a child I was taught that AM receiver resonates only with the radio frequencies it is tuned to, and "passes" ...
1
vote
1answer
308 views

AM vs FM radio under bridges

I know what the difference between AM (Amplitude Modulation) and FM (Frequency Modulation) radios is. However, I noticed that when I drive under a bridge while listening to a station on AM, it just ...
0
votes
2answers
257 views

Does a simple copper wire with an AC current create EM waves?

I want to know if a household AC current flowing through a simple copper wire will radiate EM waves? If yes, up to what range and can they be called radio waves?
3
votes
2answers
284 views

What does an analog voice transmission look like in the visible spectrum?

Analog radio signals are transmitted using light in the radio area of the spectrum. If it was transmitted using the visible spectrum instead (using a visible light emitting device instead of a radio ...
1
vote
3answers
490 views

Is it possible to produce gamma radiaton using radio emitter?

As in the title, I'm wondering is it possible. I think it is possible, because we have powerful enough radiotechniques and gamma radiation are just EM waves, not particles. However I think is ...
0
votes
2answers
52 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
32 views

Which power should a radio transmitter have to overcome attenuation of 100 km thick ice crust?

Imagine I put a floating probe inside the subglacial ocean of Encelado or Europa: how much power should my radio have to be able to communicate from external surface with the probe? Or, in different ...
1
vote
0answers
120 views

Can I detect/measure strength of a FM radio wave using a Electro magnetic field meter?

I understand that an alternating current produces an Electro magnetic field . The strength of this magnetic field can be measured by measuring devices. What I wanted to understand is Are the FM ...
0
votes
1answer
47 views

Max. speed that a space probe can communite with the Earth?

Question: Which is the average or maximum speed of a telematically sent message that a space probe can send? Is as simple as radio waves travel at the speed of light in a vacuum? Context: I have been ...
8
votes
2answers
286 views

How is extremely low frequency (ELF) radiation collected by a submarine antenna?

The U.S. Navy Project ELF managed to generate extremely low frequency (ELF) radiation at down to $\approx 76$ Hz (implying a wavelength of $\approx 3,945$ km!). I was curious, what kind of receiving ...
9
votes
1answer
664 views

Why does my body create interference with my clock radio while in bed?

I typically listen to NPR in the morning from a clock radio next to my bed. There are days when just moving my body, even my arm or leg, is enough to cause interference with the radio to dramatically ...
0
votes
1answer
85 views

Is it possible to clearly receive weak signal from space?

Imagine there is communication satellite on geostationary orbite. It transmits signal in a defocused beam, "illuminating" whole Earth hemisphere it's floating over. For example, signal is ...
2
votes
1answer
61 views

Import of Celestial Effects on Satellite Radio Interference

Some internet (among other) infrastructure comprises satellites, which beam communications in radio frequencies. These satellites, to ground observers, appear as very small solid angles in the sky. ...
0
votes
0answers
78 views

High Frequency radio wave propagation time

What is the maximum time for an HF radio wave to reach its destination regardless of propagation mode? Since electromagnetic waves' speed is close to the light speed in the air, can we say it is ...
1
vote
3answers
234 views

Are communications between computers faster by electrical signals via copper cables or electromagnetic signals?

Assume that there are two computers which are connected with a copper cable, e.g. Ethernet. Also, there is a radio connection between them, e.g. AM radio, in order to exchange data. When we try to ...
3
votes
1answer
679 views

Radio vs optical telescope imaging

As I understand, the visible light from an optical telescope is focused on a sensor which correlates light exposure to an electrical voltage, which is then converted to an image. A single antenna ...
8
votes
2answers
266 views

Does a radio receiver add a load to the transmitter?

If I have a dynamo connected to a switch and a load (such as a light bulb), the load on the dynamo is increased when the switch is closed and the light comes on. The dynamo gets harder to turn. Is ...
0
votes
0answers
56 views

Frequency response of the wireless channel

We know that the signal attenuates out with distance and according to the channel transfer function or frequency response, the signal frequency components attenuate to different values based on ...
2
votes
2answers
354 views

Radio Transmission distance (FM) [duplicate]

I am trying to find a formula (if one exists, and this is the right place) to try and calculate how far a radio station can transmit, under ideal conditions. I have searched Google, and I can not find ...
0
votes
1answer
538 views

What is the 1977 Wow signal? [closed]

Can someone explain about the 1977 Wow signal? I know that it is a signal received from space in 1977, in the form of a series of code "6EQUJ5". I would like to know if there is any thing or event ...
2
votes
5answers
1k views

Radio antenna producing waves in the visible spectrum

If a radio could produce waves in the visible light spectrum, what would the result be? This is a thought experiment that I've pondered for a few years now. I realize there are a few/many real-world ...
1
vote
0answers
50 views

I've been reading that it's possible to create a “mostly magnetic” wave, and I have a few questions

Would it be possible with the "mostly magnetic wave" to have it behave in such a way that it would be undetectable by radio triangulation? I read about the monument at the CIA headquarters that was ...
6
votes
3answers
288 views

Can visible light be emitted from a non-thermal source?

I was reading about thermal and non-thermal radiation and I was wondering if visible light can be emitted from a non-thermal source?