ADSL works over wet string (2017)

Re:ADSL works over wet string (2017) by leoedin on Saturday December 04, 2021 @04:22PM (#29444449)

Radio waves down a wire are by definition AC. Otherwise they don't work. The voltage must change, thus the current must change, thus it is AC. Just because it's not 50/60Hz AC like a powerline doesn't change that.

There might be a DC component, but ultimately all the ADSL modem cares about is the AC part.

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Re:ADSL works over wet string (2017) by Eelongate on Saturday December 04, 2021 @07:24PM (#29445620)

Couldn't you send an amplitude modulated signal down a DC line by modulating the voltage but keeping that voltage always above zero? If the current never actually reverses, it wouldn't be AC as I understand it. It would be PDC, pulsed direct current.

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Re:ADSL works over wet string (2017) by goodpoint on Sunday December 05, 2021 @05:41AM (#29448262)

> modulating the voltage but keeping that voltage always above zero

In signal transmission theory people almost always think in terms of frequency ranges.

Any DC component is simply a frequency set to 0 - that can be ignored.

Similar to the earth magnetic field when talking about radio transmission in air.

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Re:ADSL works over wet string (2017) by Eelongate on Tuesday December 07, 2021 @12:30AM (#29469343)

Sure, but it's still not AC. It's VDC or PDC, not AC. It's not AC if the Current isn't Alternating.

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