[tantony]

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.

[tomsto]

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.

[oldbbsnickname]

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

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

[eternityforest]

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.