Questions tagged [radio]

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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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1answer
75 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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10 views

Minimum detectable signal of base station in free space

I am studying for tomorrow's exam (Communication Systems, part of Computer Science course), and I've run into this question which involves some radio propagation physics. That's why I decided to post ...
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39 views

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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How to simply explain correlation between Range, Power and Bandwidth in RF Technologies?

First off, I don't have a great understanding about the physics behind radio frequency technologies. I'm working on a paper evaluating if LoRa infrastructure can help developing communities for a ...
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Dicke switching for radars

A question about Dicke switching for e.g. radio antennas. Some background so that we're all on the same page: fluctuations in the gain of the detector can dominate the low power signal. Dicke ...
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1answer
84 views

How to explain mobile phone rings inside microwave oven?

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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1answer
46 views

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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2answers
43 views

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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22 views

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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1answer
53 views

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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1answer
88 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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92 views

Difference between low and high amplitude waves

What would be the difference between radio waves produced by a walkie talkie with a range of 10 meters (lets say) versus a radio wave antenna placed at the top of a hill. I assume the antenna produces ...
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Soliton wireless comunication

What advantages could wireless communication based on spin solitons provide? https://www.nist.gov/news-events/news/2010/09/new-wave-spin-soliton-could-be-hit-cell-phone-communication Could it allow to ...
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1answer
139 views

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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14 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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31 views

What is Coupling factor in terms of frequency

How is C defined in terms fo frequency? So the power gain of a resonator ring is : $$\text{Power Gain}=\frac{C^2}{|1-T\sqrt{1-C^2}|^2}$$ $C =$ coupling factor, $T =$ attenuation. How do I modify the ...
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142 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 ...
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1answer
58 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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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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26 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 ...
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32 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?
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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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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 ...
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1answer
163 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 ...
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1answer
26 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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2answers
120 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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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, ...
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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)
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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 ...
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39 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. ...
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0answers
78 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 ...
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1answer
45 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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1answer
442 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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3answers
397 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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5answers
496 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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1answer
626 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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1answer
28 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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2answers
148 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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2answers
169 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....
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1answer
43 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 ...
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1answer
103 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 ...
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2answers
1k 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, ...
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2answers
54 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 ...
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1answer
61 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 ...
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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 ...
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2answers
98 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 ...
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1answer
137 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.
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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, ...

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