Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [modulation]

Generic term for coding information onto a carrier signal.

490 questions
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9 answers

What is the basic difference between AM and FM radio?

I want to know the basic/fundamental difference between AM and FM radio. Why nowadays FM radio has replaced AM and has become more popular?
user11832
28
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4 answers

How much data could be stored on a standard compact cassette using modern encoding?

My father and I recently dug out his old Commodore 64 from his basement and tried to revive it. Among other accessories, we also found his old Datasette drive, which is essentially a normal tape drive that can be connected to the computer to store…
DLCom
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9 answers

fastest way of doing on/off-modulation of a LED?

I need to modulate a LED quickly (multi-megahertz range) on/off. It's a high-power LED. I have had some trouble locating any well-known methods to do this. Simply switching the voltage with a FET turns on the LED quickly but the fall-time will…
Bjorn Wesen
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22
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10 answers

How exactly does AM/FM carry both pitch and loudness of voice?

Almost every tutorial on AM/FM modulation shows the modulating signal as something like a simple tone or continuous sine wave. Now that's easy, and for AM you just superimpose the modulating signal over the carrier wave as an envelope, and voila,…
aAaa aAaa
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19
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3 answers

What is Overmodulation?

The Wikipedia article is very short and doesn't explain the concept very well, and there aren't any other sites that I can find that give a simple explanation. What does it mean by 100% modulation? I understand the basic concepts behind amplitude…
Blue7
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16
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4 answers

If an FM signal has different frequencies, how does the radio receive the signal in a fixed frequency?

If an FM signal has different frequencies according to the modulation, how does the radio receive the signal in a fixed frequency like 103.2 MHz?
Yasir Mohamed
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15
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9 answers

Why doesn't higher frequency mean higher data rate?

My question is very primitive :) I've read multiple articles today and answers here, on Stack Exchange, but still don't understand one thing. Why doesn't frequency itself affect data rate in mobile networks? 3G/4G networks use QAM modulation, that…
Raiker
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14
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1 answer

Why FM stereo uses DSB-SC instead of VSB?

Using vestigial sideband instead of double sideband supressed carrier could make the baseband stereo signal more compact. Would there be any other benefits or downsides of employing VSB?
Michał B.
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13
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5 answers

Why is amplitude-modulated radio broadcast (AM) still active?

In my country (Germany) we have frequency-modulated (FM) and amplitude-modulated (AM) radio broadcasts. However, the reality is that no one ever listens to the AM since you just don't hear anything (I don't need to explain to you the downsides of…
OddDev
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2 answers

How does the plastic-tube inductor in this wireless transmitter work?

This single layer PCB (solder side shown here) is from an old fan remote: The inductor in the plastic tube is not connected physically to any components; however, the two loops of wire surrounding it are soldered to the board. This raises some…
Diractance
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11
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1 answer

What could this signal at 119.9 MHz be?

I had some fun with an RTL-SDR dongle, and I noticed this weird signal with no noticeable pattern at 119.9 MHz. What's even weirder is that the signal is symmetrical. What might this be? Or is this simply a hardware error? EDIT: This picture is…
technical_difficulty
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9
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5 answers

What does it mean for a signal to have an amplitude below 0 dB?

I am a software developer (using high level languages like .NET,C,C++ etc) trying to understand how computers work at a lower level. I understand that amplitude is always positive because it is calculated by (top-bottom)/2. However, I don't…
w0051977
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9
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3 answers

Information content of amplitude modulation versus single-sideband transmission

An amplitude-modulated radio signal with carrier frequency C, which includes frequencies from 0 to F, will use output frequencies in the range C-F to C+F, or a total bandwidth of 2F. A modulation approach called single-sideband modulation omits…
supercat
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8
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3 answers

Can Bandwidth be Traded Off with SNR in Analog Modulation?

With typical linear digital modulation schemes, we can, for a given bit rate, make a trade-off between modulation bandwidth and modulation order (effectively, how close the constellation points are). For example, let's say I require a bit rate of 1…
LetterSized
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8
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MOSFET channel length modulation - Glossing over physics

I am having trouble understanding an aspect of the channel length modulation/pinch off of MOSFETs. My current understanding (For NMOS) is that when a positive voltage is applied to the gate, the P-doped regions majority carriers, holes, are repelled…
T. K.
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