Questions tagged [transmission]
153 questions
33
votes
3 answers
Why 3 phase and not 1 phase power transmission?
Why does power transmission use three lines with three different phases? Why not three lines all in the same phase? Does it have to do with the alternators used for generating the power, or is there less loss when the phases of the three lines are…
Geremia
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22
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Single wire (no ground wire) long distance low frequency communication
In a cave we are currently exploring, there is a temporary siphon that sometimes blocks our way.
I was thinking about monitoring it (pressure sensor or other level sensor at the siphon, transmitter via mobile phone outside the cave.)
The problem is…
Sandro
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19
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10 answers
Is there any way to use half-bits?
As most people here know, by using 4 bits, we are able to count from 0 to 15 (0123456789ABCDEF in hexadecimal). But if we were to only count up to 9, we would still be using 4 bits, and the digits from A through F would be wasted.
However,…
Galahad78
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10 answers
Schematics for a simple radio transmitter that can be built only with passive components?
Fantasized in some of the survivalist, post-catastrophic novels, movies or docudramas is the radio built only with handcrafted or scraped components.
Beyond the popular appeal of this stories, I think there is a core of truth and passive elements…
Eduard Florinescu
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15
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3 answers
Are different houses out of phase?
It's hard to see but on the overhead power lines, houses seem to only be grabbing one phase of the 3-wire transmission line. If each house is using a separate phase, what makes the 3-phase system an advantage if each house still has the 0-voltage…
skyler
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15
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10 answers
Why are there only 3 wires on this power line?
When I was in Alaska, I saw a high voltage line, but I didn't see the Neutral.
Is this because the water is conductive enough next to it to use as neutral? Or is it just two Phases.
Where I live, Colorado, all of the power lines have the two…
skyler
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13
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2 answers
How does a signal travel down a telephone wire?
Supposing a computer gets data over telephone wire, it has to send/recieve signals, but how do things work?
Does it use analog signal or a digital bits?
How does it send/recieve "1"s and "0"s?
cursious10
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13
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6 answers
Simulate bad cell phone reception in the lab
I'm currently developing an internet of things device that utilizes a uBlox SARA-U260 gsm/3G modem.
In field testing, we have had significant software/firmware issues due to poor cell phone reception in our deployments in sub-saharan Africa.
I'm…
macdonaldtomw
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9
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2 answers
Why is it desirable to inject reactive power into a transmission system?
This website explains the basics of FACTS technologies and how they can be used to exchange active and reactive power with the transmission system, namely:
SSSCs - can exchange active and reactive power
STATCOM - can exchange reactive power…
Blue7
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9
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3 answers
Why does more bandwidth mean higher bit rate in digital transmission?
I understand that similar questions like this one have been asked before on this site, listed below. However, I am confused about the answers. If I explain what I think I understand, can somebody please point out where i'm…
Blue7
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8
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1 answer
Why are coaxial cables typically faster/longer than twisted pairs?
I'm having trouble understand why coaxial cables tend to have higher bandwidth compared to twisted pairs. I couldn't find any source explaining why, they just mention the fact.
For instance:
"In comparisons between coax vs twisted pair, coaxial…
Essam
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8
votes
4 answers
How can a low efficiency antenna be used for receiving but not for transmitting?
For the reciprocity theorem, if an antenna has a low efficiency in transmission, it has the same efficiency when receiving.
In literature, it is usually said that one shouldn't use a low-efficiency antenna for transmitting because a lot of power…
Tripola
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7
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4 answers
Why don't we use the Earth to transmit electricity?
Think about it, instead of transmitting electricity in 2 wires, we could only use one:
Why don't we just do it? I think they do it in three-phase transmission by connecting the neutral phase to the ground on both sides, why don't we replicate it in…
İbrahim İpek
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7
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3 answers
Why does the ionosphere reflect HF but allow VHF signals to penetrate through?
Wikipedia says:
... Unlike high frequencies (HF), the ionosphere does not usually
reflect VHF waves (called skywave propagation) so transmissions are
restricted to the local radio horizon less than 100 miles...
Why does this happen? Is it…
Everyone
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6
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2 answers
wireless transmission underwater
I am looking into constructing a closed and small device with arduino sensors that goes underwater. It has to be submerged into water and back several times, and that is made by someone with a rope attached to it. So it needs a way to communicate to…
Dani Oliveira
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