Digital electronics uses an electric square wave to create its code of bits and bytes.
A perfect square wave can be analysed as composed of an infinite number of harmonics
of its fundamental frequency.
This chart gives an indication of the harmonic content of this square wave shape.
The higher the frequency of a signal the greater is its energy and the more it radiates from a conductor.
Fn in this chart stands for the fundamental frequency which is
typically beteen 900 and 3000 ghz from these towers.