Questions tagged [radio]

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Radio Wavefront and Photons?

I have some questions related to radio waves, photons and propagation , transmission and reception. It’s my understanding a radio wave is a changing electrical and magnetic field that travels through ...
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6 votes
1 answer
564 views

Why are radio telescopes in orbit radio telescopes?

We use radio telescopes on Earth because of the atmosphere, right? It blocks the more energetic wavelengths but not radio waves and microwaves. So, since radiation like x-ray and gamma radiation are ...
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32 views

Chemical detector of radio waves?

Since there are molecules in the eye that can detect electromagnetic waves at light frequencies, would it be possible to detect radio waves (longer wavelength electromagnetic waves) biologically / ...
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1 answer
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Can radar detect electrical fields?

Can we create a radar image of electrical fields, or this is even possible? Do we need a detector opposite the emitter or does reflection work? (see figure.1)
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3 answers
92 views

How are sidebands generated in an AM signal?

I can't understand how sidebands get generated, even after reading this wikipedia page: https://en.wikipedia.org/wiki/Sideband#Amplitude_modulation This is how I picture Amplitude Modulation in its ...
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How would an AM and FM wave change when the input signal increase in loudness or frequency?

I am currently studying for the A levels and am a bit confused about how an AM and FM wave will change when the wave isn't sinusoidal and have differing frequency and loudness. I understand how a ...
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Using ham radio to communicate with an underground crew [closed]

In "Stranger things 3" Dustin uses a ham radio named Cerebro (an image https://www.reddit.com/r/StrangerThings/comments/fhrdml/will_cerebro_make_an_appearance_in_st4/) stationed on a hill ...
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2 votes
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Where does 1/20th of wavelength come from when referring to maximum mesh size that will reflect a radio wave?

In our physics class, we were taught that radio waves would reflect from surfaces even if they have gaps. Example, radio telescopes are made from mesh instead of the solid, or a microwave that has a ...
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Can we express Free-space path loss formula in the following pointwise way?

We know that the Free-space path loss formula is of the form $$\frac{P_{r}}{P_{t}}=D_{r}D_{t}\left(\frac{\lambda}{4\pi d}\right)^{2} $$ $D_{r}, D_{t}$ are the directional gains of the receiver and the ...
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6 votes
1 answer
407 views

Radio receivers and the loss of electrons

I'm reading Kenn Amdahls book "There are no electrons" to familiarise my self with the magical world of electricity. Despite Mr. Ahmdahls insistence on the non-existence of electrons, I find ...
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1 vote
3 answers
129 views

Quantum description of radio antenna

I am trying to form a clearer picture of how a radio transmitter emits waves from a quantum point of view. The classical description is quite easy: the electrons oscillate in the antenna and, as ...
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Over what distance might this device be able to interfere with car radios?

I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
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2 answers
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Is it really true that radios work better in mountaneous region than in cities?

I was recently travelling somwhere with my family. During the journey we had to pass through a mountaneous terrain. My mother suddenly switched on the radio of car and it was so clear. Is this true ...
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4 votes
2 answers
226 views

What *is* Magnetism? [closed]

Short variant: What is Magnetism exactly? Or, longer variant; As an amateur science/(hard) sci-fi enthusiast, I'm slowly but surely realizing that Magnetism feels like an "odd-one out" in ...
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Microwave relay antennas

Looking over the history of microwave relays I can see there are four distinct antenna design "periods". The very early systems used simple parabolic reflectors with dipole antennas, often ...
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2 votes
1 answer
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What is the explanation behind radio shadowing by people?

I called it shadowing but masking may be more appropriate, feel free to suggest a better question title after you read the following. I have an old clock alarm radio receiver that plays at the center ...
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Measuring radio transparency of material in relation to frequency

More specifically, I'm just wondering how I would calculate if my 16 MHz radio wave will go through a specific material (bonus points if there is a handy formula for this). My first thoughts are that ...
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1 answer
90 views

What is the most accurate instrument which can be used to measure frequency of radio waves without measuring wavelength and how accurate is it?

I wanted to know if there's an instrument that accurately measures the frequency of radio waves as I'm working on something and I didn't get anything good on web.
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2 votes
1 answer
84 views

Is there no way to bypass greenhouse gasses by converting excess heat to longerwave radiation?

The problem with greenhouse gases, as I understand it, is that they absorb and emit radiation within the thermal infrared range leading to increased temperatures on Earth. According to some sources, ...
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What is the gain of an isotropic antenna?

My question is simple: What is the gain of an isotropic antenna in dBi? I cannot find a consistent answer on the internet. Some sources define it to be 0dBi and others define it to be 1dBi. Thanks.
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Building a radio telescope!

So, I saw recently the idea of a radio telescope and thought how simple they are. So, like any other normal human being, I went on google and searched "how to make a radio telescope" and ...
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1 answer
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How to explain mobile phone rings inside microwave oven? [duplicate]

So finally tested myself and found: mobile phone rings inside microwave oven. Microwave oven frequency is 2.5 GHz which gives wavelength of 12 centimeters. Cellular network waves are even longer. Thay ...
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1 answer
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Need 50Hz detection antenna for reception of AC mains signal

Anyone know how can i design antenna for electric field detection. i m trying to make contactless Ac mains Detector which range is near about 1-mtr long. my question is about possibility of antenna ...
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1 vote
2 answers
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Would Radio Communications Between Parties Experiencing Time Differently Be Compressed/Stretched

This is a contrived and extreme example that is likely not even possible, but I'm hoping the answer will help me understand something about communications across relative time. Imagine two individuals ...
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1 vote
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Is it possible to filter radio-waves using another radio telescope?

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
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1 vote
1 answer
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Do metal objects improve radio signal reception when standing nearby?

I have a watch (Casio G-Shock GW-M5610 ) which can synchronize itself to radio time signals. In my area it uses DCF77 tower, which transmits 77.5 kHz (approximately 3868.3 m wavelength) signal: The ...
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-2 votes
1 answer
111 views

How to hide radio communications between airplanes? [closed]

I have 2 airplanes and I would like completely hide the communications between them. There is a possible way that this communications would not be detected by our radio receivers around the world? ...
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Modulation Index of an AM wave

I have been given a question as RMS value of an RF(Radio Frequency) voltage after amplitude modulation to a depth of $50$% by a sinusoidal voltage is $80$ Volts. Calculate the RMS value of modulated ...
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25 views

How does Tx Power affect the Free Space Path Loss model?

On this website one can use the FSPL model to calculate the Path Loss. This is typically interpreted online as the theoretical signal strength (in dB) that one may receive (e.g. from some WiFi). ...
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5 votes
1 answer
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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 ...
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2 votes
1 answer
110 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”?
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1 vote
0 answers
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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 ...
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40 views

What is the “single pulse radiometer equation”?

This document https://arxiv.org/abs/1601.03547 refers to the “single pulse radiometer equation”. Apparently, it’s used to calculate the flux of radio transients. What is the “single pulse radiometer ...
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1 answer
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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?
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1 answer
432 views

What’s the difference between fields of view (FoV) and instantaneous field of view (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 ...
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1 vote
1 answer
43 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?
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-1 votes
2 answers
236 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 ...
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1 vote
1 answer
37 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, ...
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1 answer
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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)
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1 vote
2 answers
50 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 ...
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0 answers
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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. ...
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1 vote
0 answers
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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 ...
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0 votes
1 answer
84 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 ...
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0 votes
1 answer
910 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. ...
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2 votes
3 answers
564 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 ...
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2 votes
4 answers
815 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 ...
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2 votes
1 answer
1k 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. ...
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1 vote
1 answer
40 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 ...
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1 vote
2 answers
209 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 ...
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-2 votes
2 answers
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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....
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