Earthing Of A Radio Mast

It all depends on the purpose of the "Mast"

If it is part of the antenna (sends and receives) it must be Insulated (isolated) from ground. Also, it must have a high-power bypass for lightning strikes (protects the electronics)

http://en.wikipedia.org/wiki/Mast_radiator

If it is simply supporting structure, it needs to be grounded much the same way a house is grounded with a long electrode imbedded deep into the ground

see http://ecmweb.com/mag/electric_dont_signals_crossed/

There are many systems for effective earthing but one unique method that I would like to comment on, and is very effective where there is a tall (200 ft + ) mast that is erected with the associated radio equipment and building located directly beneath.

The trick, in this application is to extend the Guy wires over the building to anchor points beyond and then earth them at the anchors. This provides a natural cone of protection to the building because it is included in any earth voltage rise that may occur from a lightning strike to the mast.

Special isolation is required to any power or communication lines that extend to remote earthing points outside the protected area.

Note the building grounds are bonded to the base of the mast.

A radio mast antenna frequently requires radial wires in the ground to balance the radio waves broadcast by the antenna proper.

A copy of The ARRL Antenna Book, and ARRL Radio Amateurs' Handbook is essential to the library of radio broadcasting enthusiasts.