Stack Exchange Network

Stack Exchange network consists of 175 Q&A communities including Stack Overflow, the largest, most trusted online community for developers to learn, share their knowledge, and build their careers.

Visit Stack Exchange

Questions tagged [radio]

The tag has no usage guidance.

-1
votes
0answers
25 views

Can your head be used as an amplifer/transmitter for all signals?

Ok. So I saw this video on 60 symbols about using your head to amplify the signal for a keyfob. http://www.sixtysymbols.com/videos/car_key.htm However, it got me curious, could this work for other ...
0
votes
0answers
19 views

About Radio Frequency and in human electrodes [closed]

I did xray images of my body found electrodes going near my lungs it connects to my nerves system i found out it works on radio frequency from long distance believe cell towers i think it works on 3 ...
1
vote
1answer
87 views

Why was the imaging of M87 black hole easier than imaging the Milky way's Sagittarius A*? [duplicate]

In the recent EHT press release of the image of the super massive black hole at M87, I am curious to know why the super massive black hole at the centre of milky way has not been imaged yet.
2
votes
1answer
61 views

Naive question about Analog and Digital Signals

I have just started telecommunications in high school Physics. We are currently studying analog to digital conversion. I have 2 questions : How is a "digital" signal transmitted? As far as I know, ...
1
vote
2answers
45 views

How can be various frequencies in one place?

How can we receive different radio shows in one place, they are coded in phase or frequency or amplitude of electromagnetic waves, but shouldnt elecreomagnetic waves interact each other, and all ...
2
votes
2answers
82 views

Is it possible to use visible light to transmit “radio” like AM/FM?

When I see a big radio antenna, I like to imagine it's a giant incandescent light bulb filament in the vertical, but of a invisible light. So that it "glows" the radio, performing oscillations which ...
12
votes
2answers
491 views

Why does a green stoplight interfere with FM radio reception (more than yellow)? [closed]

While listening to an FM radio station (frequencies between 88 and 108 MHz) in my car, I've noticed that as I pull up to a red light, there's an increase in the amount of noise. It's very noticeable ...
11
votes
7answers
1k views

Why are longwave radio towers so tall?

They are often in the hundred meters high. See the wiki link: https://en.wikipedia.org/wiki/Longwave Why are they so tall? Because the wavelength is long, so the antenna should also be long? But to ...
1
vote
4answers
115 views

Can we create a 20 Hz EM wave?

The electronic spectrum we study on our textbooks starts from radio waves of an order of kilohertz. But is there a lower limit for EM radiation? Cant we create EM wave of any frequency from minus ...
0
votes
1answer
26 views

Why is $Q$ factor an important quantity for electrical oscillations transmitting radio waves?

My textbook says that "$Q$ factor is an especially important quantity for electrical ossicilations trasnmitting radio waves. When selecting radio and television stations it is essential that the ...
0
votes
2answers
274 views

Why radio waves from radio-stations don't interfere with each other?

I know that radiowaves from radiostations are modulated either F.M or A.M . Lets suppose they are F.M and one has carrier wave frequency of 100 Hz and other 200 Hz they have F deviation of 20Hz/V . ...
2
votes
2answers
146 views

Is this the correct way to apply an inverse square law to radio wave propagation?

This question is vaguely a follow up to this one and this one. If I have a completely flat surface with a radio transmitter with 500 W ($\approx$ 57 dBm) of power, broadcasting on a frequency such ...
1
vote
1answer
62 views

Does attenuation to RF waves increases with frequency?

I heard somewhere that RF waves at high frequency such as above 2GHz face more attenuation while passing through air, buildings and due to humidity as compared to 800Mhz and 2) Waves at 30-40GHz ...
1
vote
2answers
90 views

How are RF Waves transmitted?

What is the mode of transmission for RF waves at 1800 MHz. Is it ground wave propagation, Line of Sight Propagation or Atmospheric reflection (from ionosphere). What are the different ways for ...
0
votes
1answer
52 views

Why is power density of RF waves measured in m2?

Why is power density of RF waves measured in m2 or cm (Area) and not in cm3 or m3 (volume) ? I mean aren't those waves travelling (radiating) in 3D space? I am new to this topic so please pardon ...
0
votes
4answers
179 views

How do radiowaves have constructive/destructive interference?

When you have radios you often find interference happening. As far as I am personally aware radio waves are the only waves that I am sure can interfere. If all EM apply do put it in that perspective ...
1
vote
1answer
70 views

Why we don't utilize most of the radio or microwave spectrum?

WiFi is from 2400-2500MHz or from 5000-5100. Fm Radio is 87-108Mhz, Phones : 450-3400Mhz But most of the spectrum is "wasted". For eg - Why we don't use above 5Ghz?
-2
votes
1answer
65 views

Why does a battery powered radio's volume go down as batteries age, even when the batteries' voltage is constant?

A set of batteries are used for a long period of time. Explain why the volume of a radio is low even though the voltage of the batteries is the same as when they were first bought.
0
votes
2answers
42 views

Is there a quantifiable tradeoff (in terms of effective broadcast distance) between the height of a radio tower and the power of the transmitter?

I have a dataset on radio stations with the following variables: the power of the transmitter, in watts the coordinates of the radio tower I can easily get the elevation at those coordinates and the ...
62
votes
4answers
12k views

What's the physics behind XKCD #2027 (time between lightning flash and radio wave burst)?

XKCD usually has solid (and often contemporary) science behind it. Lightning Difference, #2027 one says: Q: What’s that trick for telling how many miles away lightning is? A: Just count the ...
0
votes
1answer
253 views

Radio waves collision versus waves in a pond collision

Please see the attached picture: We are trying to show an image to visualize radio wave collision and interference with regards to Maritime AIS Technology. What do colliding radio waves have in ...
0
votes
1answer
37 views

Radio waves and walls

I am new to here. I am not familiar with physics well, but since this question in my opinion does not seem to belong to ELL, kindly pardon me to ask here. When given such a sentence below, radio ...
2
votes
2answers
53 views

Can we determine the distance from a radio station (antenna) and a receiver using radio wave ?

say we have the a receiver and radio antenna can we calculate the distance between the receiver and the antenna by a receiver if we know the frequency ?
6
votes
3answers
418 views

How did Jocelyn Bell aim her radio telescope (phased array)?

In 1967 Jocelyn Bell discovered pulsars using the Cambridge University radio telescope - a two hectare field of posts and wires. The pulsar was found to be in the constellation Vulpecula. How did ...
0
votes
0answers
45 views

Radio wave detection timing

Hypothetical: I have a simple LC tuned resonant circuit, with the antenna attached to one end of a tuned parallel LC, and ground to the other, and the results amplified and passed into some kind of ...
0
votes
2answers
409 views

Radio wave behaviour in reflection, Refraction and Diffraction

I am trying to understand how radio waves behave when reflected, refracted and diffracted. I have put together a list based on light which I think will be the same. Can anyone tell me the behaviour of ...
1
vote
0answers
114 views

Why does a radio's tank circuit frequency match the emitted EM wave freqency?

I am trying to understand some of the specifics of RF radiation. I am concerned with the normal antenna-emitted EM waves, no relativistic charges, no Bremsstrahlung involved. The tuning of a tank ...
0
votes
1answer
43 views

Radio light/radio wave light: what does this mean?

What is radio light and radio wave light? Is this a term? There is nothing on the internet that goes by this. I need an explanation as to what this term means and why my professor keeps using it. ...
2
votes
1answer
55 views

Photon spins from Radio Antennas

I’m a radio amateur (ham). Let us consider a half wavelength horizontal dipole antenna in free space – say at 10MHz and look at its far field. Conventional high school physics says that because the ...
2
votes
1answer
295 views

Why can radio telescopes use wire mesh as their parabolic dish?

Radio telescopes use wire mesh to save cost. How does that work? Won't the waves go through the gaps?
-3
votes
2answers
114 views

What's the maximum distance that a radio wave can travel at full power [closed]

If the sun is eight minutes away if you are travelling at the speed of light, since that's how long it would take for people to notice if the sun had stopped shining, how far can a short-wave radio ...
0
votes
3answers
105 views

Trouble in understanding AM modulation

Amplitude modulation is in fact, superimposing the low frequency transmission signal into a high frequency carrier signal, right? So, if the transmission signal can be represented as $c(t)=A_c \sin (\...
4
votes
1answer
77 views

Receiving AM radio through household wiring

A friend's post on FB made me recall a similar situation. In his case, his IR-linked headphones now play a local AM station at very low volume whenever he's near an electrical outlet or switch in his ...
1
vote
0answers
52 views

Magnet on a piezo - Can this oscillating field give me a radio transmitter?

I can read on wikipedia that radio waves are of frequency 3kHz-3THz. I know that piezoelectric actuator can reach eg. 20 kHz. What would happen if I put a small neodymium magnet on a piezoelectric ...
0
votes
1answer
70 views

Nuclear Reactor Meltdown vs Radio Waves

So my lecturer was discussing the use of robotics to deal with the fallout from either decommissioned nuclear reactors or reactors that have gone into meltdown (the example here being Fukushima). Of ...
2
votes
1answer
59 views

Why tilting a radio makes it play?

I was helping my mother in making her radio play. There was no technical issues with the radio, but it would go crazy when a nearby tubelight was switched on. We tried many things, adjusted the ...
0
votes
1answer
99 views

How do Antennas receive information?

Do wireless signals (Wifi router, radio, telephone) send their information in single "blinks" or in a continuous wave with frequency modulation or Amplitude modulation? If a radio for example needs ...
1
vote
2answers
660 views

Attenuation of radio frequency transmissions in space

In a science fiction movie some aliens come to earth and when asked why, they say they received our radio transmission and came to investigate, the radio transmission being the first television ...
0
votes
1answer
48 views

Why do regulations exist for radio broadcasting?

I've heard many times said as an argument in favor of broadcast regulations that the radio wave medium (the atmosphere/ground) will become "polluted" if people send radio signals at whatever frequency ...
-1
votes
1answer
372 views

Can Amps be used as a unit of measure for the amplitude of an EM wave?

As far as I know the definition for the amplitude of a wave is the distance between the line $y=0$ and the peak of the wave which in most cases is going to be a unit of length. I also understand that ...
0
votes
1answer
42 views

Radio Magneto Tellurics: role of reflection

In the technique of radio magneto tellurics (RMT), plane wave EM radiation incident upon Earth's surface is used to measure subsurface properties. I have read a number of different sources on the ...
1
vote
1answer
36 views

When labelling the axis of an AM Signal's frequency spectrum diagram, how can I calculate the frequencies? [closed]

If I have an AM signal with the following carrier and message tones; Carrier: Vc = 120 cos(2π 0.5 x106)t Message: Vm = 40 cos(2π 4 x103)t With a system resistance of 50 Ω, I can calculate the power ...
1
vote
1answer
330 views

How feasible is it to track down source of number station radio signals ?

How is it possible and how accurate is it to track down the origin of radio signals used by number stations that emit all around the world (and, as a bonus, how much does it cost approximately) ? I'm ...
3
votes
1answer
83 views

Can a radio station's wavelength be measured by driving through its interference?

The other night, while driving I was listening to KGO radio. KGO is a San Francisco AM station that broadcasts at 810khz. I was driving north, away from the station, at about 70mph. I notice that the ...
0
votes
2answers
363 views

How do radio-frequency transmission work?

Are sound frequencies (20-20,000Hz) included in radio waves? If not, how does sound get to our end (radio/receivers)? Is there some type of encoding going on inside those radio-frequency waves or ...
1
vote
1answer
214 views

How does the Hertz Oszillator create radio waves?

In his proof of the existence of radio waves Hertz used the setup depicted in the following figure: A sparc is created at regular intervals when the induction coil (2) creates a potential difference ...
0
votes
1answer
70 views

Can we use the radio telescope LOFAR to detect the FRB?

Can we use the radio telescope LOFAR to detect FRBs (Fast Radio Bursts)?
1
vote
0answers
358 views

Amplitude changes in frequency modulation

What would happen if the amplitude of the carrier wave in FM waves was changed? Would the signal just be stronger or would radios made for a normal amplitude not be able to decipher the signal? From ...
7
votes
1answer
309 views

Cell phone ring made nearby speaker to create strange noise [duplicate]

I was sitting on my chair in office when my cell phone rung. Somebody was calling me, so there was a caller tune which was played. But then I realized my speakers were producing strange sound when ...
1
vote
1answer
71 views

HD TV Signal reception at night

Why is on air HD TV signal reception better at night? During the daytime the reception of HD TV broadcasts is markedly lower than at night with the same antenna position. Does the sun have components ...