Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [frequency]

How many times something happens per second, measured in Hz (hertz).

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Serbia, Kosovo power grid row delays European clocks. Why?

According to this article (and a lot more published today on the same topic), Kosovo electricity net production balance has decreased during the last weeks. This has led to a small deviation of the European network’s frequency (from 50Hz to…
Evariste
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What's special about 14.31818 MHz?

While desoldering useful components off of old computer hardware, I found quite a large number of 14.31818 MHz crystals. This seemed odd to me. Why use such an irregular frequency with a very nontrivial conversion to human time units? At first I…
FlashCactus
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Why do utility companies supply at a frequency of either 50/60 Hz?

It just struck me that Utility Companies world-wide supply domestic users at either 50/60Hz. It could have been selected to be 10 Hz, or 100 Hz ... whatever Was 50/60 chosen at random? Is there some rationale involved (efficiency, easier to…
Everyone
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Why does a faster clock require more power?

If you overclock a microcontroller, it gets hot. If you overclock a microcontroller, it needs more voltage. In some abstract way it makes sense: it is doing more computation, so it needs more energy (and being less than perfect, some of that energy…
Jack Schmidt
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How did 455 kHz end up being a commonly used IF (intermediate frequency)?

Of all possible IF frequencies, why did so many consumer radio and amateur HF radio manufacturers (and filter component vendors, etc.) end up converging on 455 kHz as the IF frequency, from the vacuum tube era, and onward? Is there something…
hotpaw2
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Negative frequencies: what is that?

I know that when the frequency is 0, the voltage will be pure DC. But in DSP and Digital Communication, I have seen mentioning of negative frequencies which I dont quite understand. For example, like \$ -f_{0}\$ to \$ f_{0}\$ frequency range. How…
0xakhil
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Can I turn Radio waves into light?

Wikipedia says that the frequency of light is 300 THz. I've made a radio waves transmitter that transmits about 100 MHz. If I increase the frequency of the transmitter to 300 THz, will the antenna produce spark or light ? Can I do this circuit…
Michael George
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Why does 60 Hz mean 60 refreshes and not 120?

A light bulb using alternating current at 60Hz turns on and off 120 times per second but in a monitor 60Hz means 60 refreshes per second. Why is that? Shouldn't 60Hz mean 120 refreshes?
isar
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How precise is the frequency of the AC electricity network?

If I make a digital clock which first detects the AC frequency roughly (whether it is 50, 60, 100Hz, etc), then uses it as its clock pulse source, how precise would it be? Would it work world wide precisely? For instance, in USA, what is the mean…
hkBattousai
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Why do power grids tend to operate at low frequencies like 60 Hz and 50 Hz?

I understand that a two-pole AC generator has to rotate at 3600 rpm (60 Hz USA) in order to maintain a 60 Hz frequency and higher frequencies would require these generators to spin even faster which could be problematic. I also understand that…
ZekeC
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How to convert AC to DC

I am designing a circuit that needs to output 5VDC @ 1A. I'm trying to use a wall transformer to step the voltage down to 12VAC. The next step is the diode bridge and ripple capacitor. The ripple voltage equation is: $$V_{ripple} =…
Robert Deml
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What are 12.000393 MHz crystals used for?

I found them on www.digikey.com, and they're apparently made by different manufacturers, so there must be some use for them. What are they used for? edit and why? The 2400 baud modem doesn't offer an explanation: a 12 Mhz crystal is better for that…
Federico Russo
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Why do push button telephones use dual-tone for signalling?

Here is a related information from wikipedia: For touchtone service, the signal is a dual-tone multi-frequency signaling tone consisting of two simultaneous pure tone sinusoidal frequencies. Above shows that if one pushes number 1 he sends…
user16307
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Where do overtones in a 555 generated square wave come from?

I have built a 555 oscillator and connected it to a speaker. Using an oscilloscope I adjusted the 555 to generate a 2.5kHz square wave. I then held a microphone up to the speaker and fed the input into a spectrum analyser. What I expected to see was…
JShorthouse
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Why is the bitrate of infrared smaller than the bitrate of WiFi?

Infrared has a frequency of 300 GHz – 430 THz, while WiFi has a frequency of 2.4 GHz or 5 GHz. As the frequency of infrared is greater than the frequency of WiFi, the transfer rate (bitrate) of IR should be greater than WiFi. In reality, IR…
Muhammad Ikhwan Perwira
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