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13
votes
2answers
2k views

How do you make a spherical radio wave?

A vertical rod, a usual dipole, produces radio waves in the horizontal plane, mostly in two opposite directions: If that is possible, how do you produce a spherical EM radiation? should the ...
-1
votes
1answer
38 views

Can video data can be transmitted via radio frequency? [closed]

My friend says that it's possible to transmit an video by converting it's data to radio frequency?
0
votes
0answers
8 views

Colpitts oscillator

why colpitts oscillator is used for fixed radio frequency?I think they are used because it produces frequencies in the radio spectrum am I correct
3
votes
1answer
40 views

From how far away could Earth's telescopes detect Earth like radio signals?

The Earth has been broadcasting human generated radio signals for about 100 years now. If a nearby civilization were broadcasting similar radio signals, could we detect them with our own radio ...
0
votes
0answers
17 views

Length of a transmission line for a known Zin, Z0 and Zload

From the transmission line equations i have the following impedance transformations equation: $$\ Z_{in} = Z_0 \frac{Z_{load}cosh(\gamma) + Z_0sinh(\gamma)}{Z_{load}sinh(\gamma)+Z_0cosh(\gamma)} $$ ...
5
votes
1answer
54 views

Why are magnetron apertures in home microwaves so small?

I'm curious why magnetrons from a home microwave like in the image below can have an aperture between the magnetron cavity and the waveguide that is significantly smaller (2-6mm usually) than the ...
1
vote
1answer
47 views

Why doesn't a transmission line mess up an antenna resonance?

I don't understand why the resonance of an antenna is not affected by the transmission line to the receiver. For example, given a dipole antenna like the following: The antenna length is carefully ...
6
votes
1answer
197 views

Why is UHF so much more popular than other frequencies for radio? [closed]

Great most of popular radio stations nowadays operate in UHF frequencies. I know this was not the case in the past, long, medium and short wave radios much more popular (and AM encoding being quite ...
0
votes
0answers
17 views

Can electroluminescence be theoretically used for RF communication?

I know that photon energy of radio frequency, 3 kHz (1.24e-11 eV) to 3GHz (1.24e-3 eV), is much smaller than the thermal energy $k_B T$ at 300K (25.8e-3 eV), which in turn is much smaller than typical ...
0
votes
2answers
66 views

Can we determine the location of a radio station if we know the wavelength and frequency of radio wave emitted by that radio station?

let say that we can detect the wavelength and frequency of radio wave then can we detect that from where these radio waves are coming or from how much distance these waves are coming?
1
vote
0answers
26 views

Is it possible to make an antenna that's more compact than a split-ring resonator antenna? [closed]

I'm aware that a split-ring resonator antenna works efficiently by being half the size of a classic antenna. But is there any design that takes even less space? I have in mind millimeter or micrometer ...
0
votes
1answer
19 views

Why is the modulating shape appear in both sides of the carrier signal in AM?

It's about Amplitude Modulation. Can anyone tell me why is this signal wave or modulating waveform shape appears in both sides of the carrier sine wave? Why not in one side only? $$x_c(t) = A_c[1 + ...
1
vote
1answer
30 views

Low frequency video transmission

Can a video signal be transmitted for a short distance ($30\,\mathrm{cm}$) by a very low frequency carrier ? Here my concern is about frequencies $1\,\mathrm{hz} - 100 \,\mathrm{hz}$ . Transmission ...
2
votes
0answers
32 views

Wavelength, frequency, and radars [closed]

I'm doing a high school paper on the effects of frequency alterations on a radar image. Can someone recommend a book which I can use?
0
votes
1answer
47 views

Why do radio stations have ranges

If you have been on a long car ride you would know that the signal of a radio station becomes weaker and weaker and then stops. But since radio waves are just a wavelength of the electromagnetic ...
0
votes
0answers
18 views

Injection current modulation with a modulated RF signal to drive laser

I am using an RF modulated injection current to drive my laser in such a way that the modulation index = 0.8. At this point, I see the carrier and first sideband on the spectrum analyzer. If I now ...
0
votes
0answers
11 views

How do i calculate the “attenuation effect” that of a perforated aluminum sheet?

I am conducting an experiment test different configuration of perforated aluminum sheets. I am working with radio waves but i am having am hard time finding any equations or properties for this ...
0
votes
1answer
65 views

RF disturbances produced by transmission power lines

I need a book or paper that contains "the effects of transmission lines on the radio frequency transmission and disturbances". Could you help me find a useful textbook? Thank you
0
votes
2answers
290 views

materials that can render Bluetooth useless

i'm currently preparing some experiments about using Bluetooth in real life. And to make the data more vary, i need some materials that can really giving side effects to Bluetooth functionality. i've ...
1
vote
0answers
36 views

How to describe frequency spectrum with samples?

I posted this same question in math, but nobody is answering, so I thought I'd give a try here too... To me the question is pretty straightforward, but nevertheless I have to explain its background ...
2
votes
1answer
108 views

How do NFC/RFID devices transmit data?

I am designing an NFC device but am still a little unsure about the principles behind NFC/RFID. From what I understand: A primary coil constantly emits a 'carrier frequency' magnetic field. This ...
1
vote
1answer
82 views

Light / TEM wave in a hollow waveguide

I'm cramming for my EMF exam, and a question came up: Light in free space is an example for a TEM wave, isn't it? (Maybe thats already my mistake) And we learned that in a hollow waveguide only TE ...
0
votes
1answer
180 views

Cantenna and waveguide

I'm studying for a lecture of RF and wave guides and i'm currently building a cantenna. I have two questions about it construction and on how it works. My questions are about the lengths of the ...
1
vote
1answer
124 views

Do neutron stars produce sound?

I've watched a video on youtube about neutron stars as called (pulsar) and it claims that pulsars produce this sound. then i found that they produce radio waves which can be converted to sound. Radio ...
0
votes
0answers
19 views

My microwave oven disrupts my bluetooth connection even when I'm 12ft away. Should I be worried? [duplicate]

I often wear bluetooth headphones that connect to my mobile phone. I work on my laptop in my dining room approx. 12ft away from the microwave oven and my mobile phone is usually in my pocket; ...
1
vote
2answers
232 views

Do Sidebands mean the frequency of an AM radio wave is not constant?

I'm studying for A-level now..... I have read some other posts explaining how the sidebands generated after the carrier wave is modulated. So, if there is sideband frequency, the frequency isn't ...
0
votes
1answer
63 views

Building a Crystal Radio Questions

I have been reading several books and articles about building a crystal radio and the explanations about the inner workings of the circuit seem vague. All articles and books mention the coil and the ...
1
vote
0answers
83 views

Discernible “frequencies” of magnetic fields that do not affect each other

Two magnets secured to a surface close to each other in a fashion such that their constant attraction to one another is counteracted by the normal force of the securement of each. Is there a way to ...
4
votes
1answer
203 views

Why does a non-contact voltage detector light up when you touch a plasma ball with the other hand?

I am doing a science experiment and we decided to try holding a non-contact voltage detector up to plasma ball. We were surprised that it would light up when it was 3 ft away from the plasma ball. I ...
0
votes
0answers
25 views

Transmitting to and from low earth orbit?

I'm a hobbyist and I'm currently thinking about building a Cubesat. I'm currently designing PCBs, casing, etc. I was wondering what variables are involved with sending data to and from 250km - 350km ...
1
vote
1answer
137 views

Does rain jam radio signal?

I have experienced several times that heavy rain seems to jam the signal a radio of a bus receives. The only explanation I have is that the rain drops also become weak emitters, if a radio wave hits ...
0
votes
0answers
32 views

Ground influence on 434 MHz radio signal

I have read in a paper that ground acts as reflector for radio signals in 434 MHz band. Why is that the case?
0
votes
1answer
51 views

How is spectrum controlled? [closed]

I understand that spectrum is considered a national resource for many governments. It is akin to land, water and other resources. It is also a scarce resource. I wonder how is it that government ...
2
votes
1answer
145 views

polarization of a transverse wave travelling in ionosphere with polarization direction perpendicular to earths magnetic field

Assume a transverse electromagnetic wave entering ionosphere such that its Electric field of wave is perpendicular to earths magnetic field. Now, i read that as it will enter plasma, the wave will ...
0
votes
2answers
71 views

Chaff-RF Relationship?

What is the relationship between chaff length and the frequency it is meant to interfere with? I've read that specific lengths of chaff are more effective as a countermeasure for specific ...
3
votes
1answer
216 views

Radio wave propagation in ionosphere

Radio communication is based on the concept that a radio signal incident on the ionosphere is reflected if the frequency of the wave matches the plasma frequency. But what exactly happens? Is it ...
2
votes
1answer
76 views

The influence of the antenna height

I am working on a model of a transmitter. The transmitter is attached to the wheel of the vehicle and thus constantly changes it's height. In other words capacitance between antenna and ground is ...
0
votes
2answers
35 views

Radioactivity features

What happens if someone would make a wire coil around nuclear reactor core? What are the possibility to capture radioactivity directly?
0
votes
0answers
36 views

Why can microwave (in microwave oven) heat the food but wifi can't? [duplicate]

As far as i know, microwave (used in microwave oven) and wifi all operate on the same frequency, but why microwave can heat the foods while wifi wave can't?
2
votes
3answers
3k views

How does the movement of electrons produce radio waves?

I'm mostly wondering about radio frequencies. I understand that voltage is the movement of electrons, and that the antenna acts as a light bulb, emitting at radio frequencies, following the reverse ...
3
votes
2answers
3k views

Why is bandwidth, range of frequencies, important when sending wave signals, such as in radio?

So in wired/wireless networking and radio, signals are sent in form of wave. Then the concept of bandwidth comes in, which is the difference between highest frequency and lowest frequency in a signal. ...
4
votes
1answer
192 views

AM Receiver and sideband frequencies

How sorry for "dummy" question. I have difficulty to understand how the AM receiver. Being a child I was taught that AM receiver resonates only with the radio frequencies it is tuned to, and "passes" ...
4
votes
1answer
244 views

Does any lower frequency electromagnetic radiation naturally reach us from the Sun?

I am not sure whether the sun originally emits everything in the electromagnetic spectrum, (whatever the relative strengths of each portion might be), but I do read that many waves, including gamma / ...
1
vote
3answers
1k views

Do radio waves interact with electrical wiring?

AFAIK radio waves can be influenced by magnetic fields (when not traveling through a vacuum). Electrical wires create a magnetic field perpendicular to the length of the wire, as a function of the ...
3
votes
2answers
429 views

What does an analog voice transmission look like in the visible spectrum?

Analog radio signals are transmitted using light in the radio area of the spectrum. If it was transmitted using the visible spectrum instead (using a visible light emitting device instead of a radio ...
4
votes
2answers
333 views

What is happening to the electrons, and E & H fields, in an antenna with a standing wave inside?

Diagrams like the one shown below are often shown to explain antenna theory, but I have always had problem with the concept of voltage being a wave, and because of this the diagrams never make any ...
2
votes
1answer
254 views

Shielding RFID with aluminium foil

I've been playing around with some contactless bank cards and an RFID reader app on my phone. As expected, if I wrap the card in foil, the reader no longer detects it. But I was surprised to find that ...
1
vote
0answers
45 views

Which power should a radio transmitter have to overcome attenuation of 100 km thick ice crust?

Imagine I put a floating probe inside the subglacial ocean of Encelado or Europa: how much power should my radio have to be able to communicate from external surface with the probe? Or, in different ...
1
vote
0answers
183 views

Can I detect/measure strength of a FM radio wave using a Electro magnetic field meter?

I understand that an alternating current produces an Electro magnetic field . The strength of this magnetic field can be measured by measuring devices. What I wanted to understand is Are the FM ...
0
votes
1answer
98 views

Radiofrequency attenuation in cold plasma

The missile plume can be considered a cold plasma. If a radio signal passes across the plume it's attenuated. Obviously the attenuation depends on the frequency of the signal. Where can I find some ...