Effects of AC FrequencyFollow
The Electromagnetic Induction article shows that the higher the frequency, the greater AC voltage and signal induced in the conductor.
The Capacitance Effects article shows that the higher the frequency, the greater the capacitance current flow and signal. So high frequencies would appear beneficial for applying a signal.
This illustration from an oscilloscope shows four different frequencies with the same amplitude i.e. current or field strength. How much change occurs within the same period of 0.5 millisecond is clearly shown, and the inductive effect will vary in proportion to the frequency.
On the other hand, because the signal current flows to ground via the capacitance more easily with increase in frequency, a given signal strength will be lost over a shorter distance of pipe or cable run.
A further drawback of high frequencies is the ease with which signals aimed at the target conductor can also be coupled by mutual induction to other conductors in the vicinity. This often makes it more difficult to trace a target conductor in a congested area.