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131 votes
2 answers
67k views

How many photons are received per bit transmitted from Voyager 1?

As of 2024, according to https://voyager.jpl.nasa.gov/ , Voyager 1 is around one light·day away from Earth and still in radio contact. When Voyager 1 sends messages to Earth, roughly how many photons ...
Craig Gidney's user avatar
  • 6,932
0 votes
2 answers
61 views

Radio waves: physical mechanism of ground (surface) wave propagation

Radio waves with frequencies below ~3 MHz can propagate as ground waves, following the curvature of the Earth to reach distances well beyond the visual horizon. However, I am confused about the ...
summer's user avatar
  • 126
0 votes
2 answers
67 views

Book Recommendation about radio frequency antennas and satellites

I have recently obtained a job in the field of radio frequency antennas and satellites, and I am interested in delving deeper into the subject. Could you recommend any books that cover these topics ...
0 votes
0 answers
36 views

Pattern of source-tracking two-element radio interferometer

In a two-element adding Interferometer, the phase difference comes about as EM-waves from a source at an angle $\theta$ to the baseline-normal generally cover different path lengths when travelling to ...
Merkel_Bot's user avatar
0 votes
2 answers
40 views

How strength of RF coupling depend on the antenna material?

If we place different materials in the microwave owen, they will get hot at different speeds. For instance meals get hot really fast. What material property decides on the strength of the coupling? ...
Mariusz's user avatar
3 votes
3 answers
2k views

The Journey of an Electromagnetic Wave Exiting a Router

I'm learning a bit of how WiFi works under the hood, and have a basic grasp of the general process. First, you make an internet request. Your computer then sends out a WiFi signal which your router ...
Loic Stoic's user avatar
1 vote
1 answer
61 views

If the speed of light is a constant value and the wavelength is constant (antenna), how can one antenna transit/receive different frequencies?

The speed of light is about 300,000,000 m/s, and the wavelength is determined by the design of the antenna, how can one antenna transmit different frequencies other than just the one defined by f = c /...
epicMan123's user avatar
0 votes
1 answer
117 views

What's wrong with solar wind?

As you know, the sun emits into the surrounding space the so-called "solar wind", consisting of plasma. In turn, plasma is a mixture of charged particles. According to the laws of physics, ...
Vladimir Orlov's user avatar
6 votes
3 answers
623 views

Impedance at Feed Point and End of Antenna

Watching this pretty great video from 1947 about antenna fundamentals. I have a question about one part of it though. The video states that the impedance at the feed point of the antenna is 72 ohms, ...
vigilante_fresh's user avatar
2 votes
2 answers
338 views

How does radio wave get reflected?

Actually recently I posted a question in h-bar ($\hbar$) relates to radio wave reflection from mirror, and one of the user replied that it can't, only ionosphere can reflect it, so my question what is ...
आर्यभट्ट's user avatar
0 votes
0 answers
241 views

Can I use a radio to light a fluorescent light bulb?

I am trying to recreate the demo in this video, titled “How to create your own aurora.” To summarize the video, a radio is used to light a fluorescent light bulb. The narrator describes the walkie ...
Moth's user avatar
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17 votes
4 answers
3k views

Does a radio receiver "collapse" a radio wave function?

Does a radio receiver "collapse" a wave function when listening to a radio broadcast generated via a transmitting antenna? Background: There has been much discussion on this forum (here) ...
kdtop's user avatar
  • 317
0 votes
1 answer
128 views

How does an extension cord on a radio apparently function as a reception antenna if placed in certain positions?

I have an old radio and the antenna broke off at some point years ago. The radio has somewhat poor reception, as the room it's in faces a courtyard or alleyway. I have to position the radio just right ...
Sketcher's user avatar
  • 113
1 vote
1 answer
40 views

Why wireless radios start making buzzing noise when I switch on some electrical appliances?

This question has possibly been asked a numerous number of times already, by many people in many places, but nowhere can I find a precise answer to my precise question. When I turn on, say a ceiling ...
QuestionTheAnswer's user avatar
0 votes
2 answers
154 views

Coaxial Confusion, what really are unbalanced transmission lines? [closed]

Thanks for clicking on my question. I do not understand how an unbalanced transmission line works. Take for instance coaxial cable which is the subject of my confusion. This confusion arises from the ...
SirStrategic's user avatar
1 vote
1 answer
48 views

Do ultrasonic motion detectors (like the Arduino sensor) detect small particles like dust when receiving waves? If they don't why is that the case?

This may be a bit of an elementary question but I've recently started studying physics for fun so this has confused me. Do ultrasonic sensors have the capability to detect very small particles like ...
Jarus's user avatar
  • 11
0 votes
1 answer
34 views

Impossible VSWR reading for inductively loaded telescopic antenna

I am trying to understand how this SWR reading with an antenna analyzer is possible: https://www.youtube.com/watch?v=PeVZFD07-xY&t=231s. For context in that video a youtuber describes how to ...
Dylan Muller's user avatar
1 vote
0 answers
41 views

Easy question regarding RF and ion traps

I saw this interesting video: https://www.youtube.com/watch?v=d-qTa_7FtAA In this video, from the 8:55 mark to 11:55, this man explains using unique frequencies for each element(?) with a unique m/z ...
Young Jun Lee's user avatar
1 vote
0 answers
25 views

Is there any mathematical model of how does rain & other weather conditions impact the radio link?

I'm looking through UAV radio-communication process and wondering if there are any formulas, describing how does the air pressure and weather itself (rainy & snowy conditions) affect the radiolink ...
Konstantin Mironov's user avatar
0 votes
2 answers
87 views

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 ...
Nick's user avatar
  • 245
6 votes
1 answer
676 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 ...
CosmeticMichu's user avatar
1 vote
0 answers
83 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 / ...
User5754448's user avatar
0 votes
2 answers
236 views

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)
RhinoPak's user avatar
2 votes
4 answers
2k 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 ...
Dan's user avatar
  • 127
0 votes
1 answer
142 views

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 ...
ezekiel's user avatar
  • 13
2 votes
0 answers
308 views

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 ...
Eugene Levinson's user avatar
6 votes
1 answer
423 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 ...
Erik Eriksson's user avatar
1 vote
4 answers
872 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 ...
Roger V.'s user avatar
  • 59.4k
0 votes
2 answers
150 views

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 ...
A. B.'s user avatar
  • 81
2 votes
2 answers
468 views

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 ...
Rahul Sharma's user avatar
4 votes
2 answers
636 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 ...
Shadowjonathan's user avatar
2 votes
1 answer
84 views

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 ...
Winston's user avatar
  • 3,236
0 votes
1 answer
449 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.
user13576286's user avatar
2 votes
1 answer
94 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, ...
Anthony's user avatar
  • 71
0 votes
0 answers
54 views

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.
Quentin James's user avatar
0 votes
0 answers
77 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 ...
CallMePluto's user avatar
0 votes
1 answer
661 views

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 ...
Dims's user avatar
  • 1,726
0 votes
1 answer
225 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 ...
Er.rht's user avatar
  • 1
1 vote
2 answers
63 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 ...
JasonC's user avatar
  • 13
1 vote
0 answers
27 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 ...
Ilya Gazman's user avatar
  • 2,127
1 vote
1 answer
471 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 ...
jhkouy78reu9wx's user avatar
-2 votes
1 answer
188 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? ...
Felipe's user avatar
  • 9
0 votes
1 answer
1k 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 ...
Jack's user avatar
  • 142
0 votes
0 answers
85 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). ...
Gouz's user avatar
  • 101
5 votes
1 answer
512 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 ...
nreh's user avatar
  • 258
3 votes
1 answer
265 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”?
PerplexedDimension's user avatar
1 vote
0 answers
23 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 ...
PerplexedDimension's user avatar
0 votes
1 answer
102 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 ...
PerplexedDimension's user avatar
0 votes
1 answer
54 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?
PerplexedDimension's user avatar
1 vote
1 answer
724 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 ...
PerplexedDimension's user avatar

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