Questions tagged [radio]
The radio tag has no usage guidance.
208
questions
5
votes
1answer
70 views
Is this a possible derivation of the electromagnetic wave equation?
Some Background:
I've been trying to understand electromagnetic waves, how they travel, and how they're produced. After some Googling and Wikipedia(ing?) I've learned that we use the EM Wave Equations ...
2
votes
1answer
34 views
What is “spectral turnover”?
In a paper which deals with the spectra of radio frequency cosmic events, the word “spectral turnover” is used. What is “spectral turnover”?
1
vote
0answers
13 views
How is VLBI delay calculated, practically?
I’m working on a research project wherein we are trying to solve a problem very similar to VLBI delay. We have two radio receivers, and we know their locations. We also know at what time one receiver ...
0
votes
0answers
14 views
What is the “single pulse radiometer equation”?
This document https://arxiv.org/pdf/1601.03547.pdf refers to the “single pulse radiometer equation”. Apparently, it’s used to calculate the flux of radio transients. What is the “single pulse ...
0
votes
0answers
26 views
Why are low-frequency radio transients so rare?
Why are low-frequency radio transient (fast radio bursts, etc) so rare? Is it due to our observational equipment, or something intrinsic to transient phenomena?
0
votes
1answer
29 views
How is the “intensity” of a fast radio burst measured?
I’ve read that Fast Radio Bursts are very “intense”, but how is intensity measured?
0
votes
0answers
12 views
Can I calculate frequency limits using bandwidth and center frequency?
I’m given the centre frequency and bandwidth of a radio transient. I need to determine the frequencies over which the transient occurred. I know there’s a relationship between the two, but I’ve ...
0
votes
1answer
28 views
What’s the difference between FoV and IFoV?
I read that radio telescopes have “huge fields of view (FoV)”, but are unable to precisely localized objects due to their “small instantaneous field of view (IFoV)”. Apparently, somehow the size of ...
1
vote
1answer
23 views
Why do high frequency radio telescope observations require precise localization?
Why do high frequency radio observations, particularly of transient phenomenon such as Fast Radio Burst and Pulsars, require increasingly precise localization with increasingly high frequency?
0
votes
0answers
24 views
How is interferometry used to measure distances?
I understand how a basic interferometer works, and how Michaelson used an interferometer to more-or-less disprove the “luminiferous anther”, but, analytically, how would one go about using an ...
0
votes
0answers
9 views
How does relative permittivity and conductivity of a surface affects the propagating wave?
INTRODUCTION
I am working on project related to atmospheric ducting, the natural phenomenon that traps the propagating radio waves, thus allowing it to travel far beyond the radio horizon with less ...
1
vote
1answer
33 views
Do long delayed echo occur on Mars and on the Moon too?
Long delayed echoes (LDEs) are radio echoes which return to the sender several seconds after a radio transmission has occurred.
Do LDEs occur on other planets and moons too? Like for example on Mars, ...
0
votes
1answer
23 views
What is a radio echo? [closed]
Simply that: what is a radio echo? And when it was first discovered?
By searching on Google I get results like Amazon Echo and Echo (radio station)
1
vote
2answers
46 views
Wireless data transmission more than a bit at a time
I'm not that educated in wireless data transmission, but, the basics of frequency modulation and or amplitude modulation are quite basic. Is there any examples of transferring more than a bit at a ...
1
vote
0answers
32 views
How do low frequency radio waves bend due to diffraction? [closed]
I did not understand how do surface waves follow the curvature of the earth by diffraction. Here is an excerpt from the book that I was reading from.
...
0
votes
0answers
25 views
Why precise localization is required for higher frequency radio observation?
I am reading an article about Fast Radio Bursts. Since most of these bursts could not be precisely localized, a majority of them are detected at 1.4 GHz. There it is mentioned that precise ...
0
votes
0answers
22 views
What part of static noise in FM radio and analog TV is due to CMB?
When you switch analog FM radio or analog TV channel to non-existing station (in-between channels),- then you hear/watch just plain static noise. Question what I am interested is- what part exactly of ...
0
votes
0answers
39 views
Natural vs. man-made electromagnetic spectral energy density
Over the past year or so, I've heard several people (not physicists) express concern over the amount of environmental electromagnetic energy from human sources like radio communication, wifi, and most ...
0
votes
1answer
33 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
101 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
99 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
271 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
237 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
26 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
83 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
119 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
38 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
85 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
418 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
50 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
59 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 ...
1
vote
2answers
67 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
127 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
81 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
138 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
704 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
189 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
83 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
1k 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
437 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
200 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
115 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
66 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
376 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
80 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
78 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.
