Rock phones?

[MNwr786]

Are there any people here that have used rock phones? Rock phones use electromagnets to send digital data through thick stone easily and are used for mine communications. Im guessing its because the magnetic flux easily passes through solid materials unlike an rf signal being attenuated by ground loss and skin effect.

Seems like a very useful way to communicate between a bunker and a house without wires or a spectrum analyzer spotting the qso.

Anyone here ever play with one???

 

[Kevin L]

We played with stuff like this in physics class, but never outside a student lab.

This will work better with some bunker building materials than others.

Be careful with this thing around pacemakers, brain induction devices (sometimes used for Parkinson's disease), insulin pumps, implanted defibrillators, and other medical devices that use electronics.

I would also be careful around cardiac monitors.

If these things are an issue, then fiber optics might be better for bunker communications.