[kwlug-disc] To WIFI or not to WIFI

[Andrew Kohlsmith (mailing lists account)]

> On Oct 6, 2022, at 5:09 PM, John Van Ostrand <john at vanostrand.com> wrote:
> If you want to get really experimental you can run Ethernet over phone wire. It'll be noisy and maybe only 10Mbps. Ethernet needs 2 pair (4 wires) ideally twisted and phone cable isn't twisted, so you can only use that for short runs.
> 
> Keep in mind that all these use frequencies somewhere in the Mhz ranges and you'll be exposed to that as well.

This is an accurate statement, but Ethernet is a differential signal and the wire pairs that carry the high frequency signals are twisted tightly together; the actual emissions from these types of signals is *very* low; it’s part of why they’re used. HDMI, DisplayPort, MIPI, USB, SATA and PCI Express also all use differential signalling.

Heck, even the electrical and magnetic fields radiated by three phase high tension lines is quite low. A properly balanced three phase power system will have a theoretical zero neutral current for a four wire (Wye) connected system (and zero neutral current in a three-wire (Delta) system. There are occasional stories about people using the overhead power lines to melt snow in their driveways by burying copper wire or stealing power by hanging a wire close to the overhead tower; these are all either flat-out fairy tales or dangerous as hell because you’d need to be AWFULLY close to one of the three wires carrying hundreds-of-thousands-of-Volts to induce enough current to be useful, and if you’re drawing enough power from one of the phases to melt the snow in your driveway you’re going to have the power company out to find out why one of the phase currents is out of balance in your neighbourhood and fix it.

-A.

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