Questions tagged [radio]
The radio tag has no usage guidance.
190
questions
0
votes
1answer
32 views
Would a small radio (RF) chip be able to communicate through a stainless steel tank?
My team is building a vacuum chamber out of stainless steel. We will be putting components into the chamber and recording temperature/pressure etc. values with an Arduino.
My question is whether we ...
0
votes
1answer
50 views
Does Carbon act as a Faraday Cage?
I am wondering if a GPS LTE-M tracker can be put inside carbon handlebars.
I know the answer essentially boils down to Carbon acting as a Faraday cage but could not find a satisfying answer to this.
...
0
votes
0answers
23 views
Commercial Radio Bandwidths around the world
I'm a liberal arts person who has more than a passing interest in radio but it has taken years for this to dawn on me, so be kind if it is obvious.
I was out of the US recently, and I saw a radio in ...
2
votes
2answers
71 views
Longest wireless transmission
I've recently been asked (by a flat earther no less) how Exalt have managed to achieve a world record data/communications microwave link if the earth is indeed spherical (which it obviously is).
I ...
3
votes
4answers
183 views
Photons of RF energy
So I start with the understanding that light is photons of electromagnetic energy, and that as the color gets more red the wavelength increases, and that an optical photon has both an electric and a ...
2
votes
1answer
79 views
Does grounded sheet metal reflect or absorb radio waves?
By "radio waves" I mean waves used for radio transmission appliances, e. g. within 1 MHz to 10 GHz.
If the size of the metal sheet makes a difference, please answer for a infinite sheet and a fridge.
...
1
vote
1answer
24 views
Wave Interference (Control Tower vs Mobile Phones)
I was curious about something regarding radio waves. When we're talking about differences of 200 MHz between waves, is there any way of any noticeable interference occurring? By noticeable I mean ...
1
vote
2answers
64 views
Why are 'low frequency' EM waves attenuated by a single layer of kitchen foil?
Can someone explain why my am radio doesn't work when covered by a layer of foil that is less than one 'skin depth' at the appropriate frequency?
According to wikipedia and other websites on the ...
-2
votes
2answers
99 views
How are radio waves different from the rest of the EMR spectrum?
Radio waves are generated by connecting high frequency AC electricity to an antenna (e.g. a dipole antenna), and we can control the frequency by the frequency of the AC. The frequency of other EMR (e....
0
votes
1answer
27 views
Is the radio attenuation of an obstructed 2.4GHz signal, dependent on its incident power?
The following figure (taken from CTS 115: Free Space Path Loss) describes generally how obstructions attenuate a 2.4GHz signal:
I would like to ask, is this -3dB loss dependent on the power (or ...
1
vote
1answer
84 views
Is it true that if one stood on Westminster Bridge with a radio, one would hear the chimes of Big Ben via the radio sooner than in the real world?
I was reading this review of Damon Krukowski’s Ways of Hearing in The Spectator when I stumbled across this claim:
“And before the renovation of Big Ben began, if you stood on Westminster Bridge ...
0
votes
2answers
226 views
How far can radio waves travel in vacuum? and light waves?
Radio wave and light wave are the same thing. They all are electromagnetic radiation, the only difference between them is frequency.
My question :
1, is there any photon-like thing for radio wave?
2, ...
1
vote
2answers
46 views
Radio wavelength to penetrate 8 ft of seawater
I am trying to penetrate about 8 ft of seawater with a radio wave. What wavelengths will work? I understand that low wavelengths penetrate seawater the best, but I am looking for a frequency that does ...
3
votes
1answer
55 views
How to calculate how far radio light goes in the ocean [closed]
Radio light is not a practically useful way of communicating underwater over large distances. My question is how does one calculate how far a radio wave at a given frequency will propaagate in the ...
68
votes
3answers
7k views
How strong are Wi-Fi signals?
My family members dislike the idea of having many devices communicating wirelessly in our house, arguing that the signals have negative effects on our physical health.
I would like to tell them the ...
0
votes
2answers
57 views
Radio Waves / Light: Atmospheric Refraction
The following image differentiates between a visual horizon and a radar horizon.
Sidenote: I'm not too familiar with primary surveillance radar
technology, but this image refers to secondary ...
1
vote
1answer
120 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
79 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
53 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
124 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
636 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
2k 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
167 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
66 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
816 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
297 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
153 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
112 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
65 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
299 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
76 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
71 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.
1
vote
2answers
110 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 ...
63
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 ...
1
vote
1answer
450 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
45 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
62 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
468 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
49 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
718 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
116 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
83 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
70 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 ...
3
votes
1answer
521 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
592 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
123 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
120 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
85 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
96 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
60 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 ...
