There are RF grounds and there are safety, (AC) grounds.
Even if you tie all grounds together, you can have inductance and hence
impedance that makes that scheme a poor RF ground.
Most antennas don't need an earth ground, consider the earth satellites,
and the space station, rockets and shuttles. (consider the Russian
transport a shuttle like case).
Majority of antennas are dipoles, complete RF systems unto themselves.
Some antennas have an image that is enhanced with earth return, ie
quarter wave verticals, where radials or a counterpoise or a plane area
The high frequency content of a lightning bolt can impart a varying
potential along a ground bus connection of various rods, and the earth
under each rod may differ in its impedance as well. Thus you can have a
potential difference even with bonding.
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