Hacker News Reader

Magnetic field drops off by an inverse-cubed law (as opposed to inverse-squared for RF). So it would be a lot more impractical to cover large volumes.

View on HN

Thanks. I would still be curious to know how the strength of an artificial magnetic field at a range of say 10 km compares to the order of magnitude of local variations they are talking about in the earth’s magnetic field.

Make some assumptions, find the relevant equations, and plug in the numbers.

https://en.wikipedia.org/wiki/Magnetic_field

IIRC I think there was a telephone system with giant magnetic coils that went a quarter mile, but maybe I read a blog wrong or something.

In any case it wouldn't be as portable and would make you rather easy to detect I would imagine, if you wanted to cover a large area.

Reply on news.ycombinator.com