Driving down I-5 between SF and LA, I've seen many radio towers that
rest on a single point.

I don't know what they are transmitting.

I do know that they look like regular towers from about ten feet up.
From ten feet and higher, they have a diminishing square cross
section. (May be triangular.)

Instead of resting on four (or three) legs though, they rest on a
single point, making the whole tower sort of a very elongated diamond
shape.

The whole tower is kept from tipping over through the use of guy
wires.

Why build an unstable tower? What are the advantages of this design?

Thanks,


Jerry