[600MRG] VLF / ELF Antenna Impedance

[Frank Lotito]

There have been some recent interesting postings on different message boards regarding experimentation around 8 KHz.  One of the authors suggested to the effect that he plans to measure the (contemplated) antenna system's feed point impedance with an R-X bridge.  Eventually he plans to dump a few hundred watts into the antenna via a yet to be constructed matching circuit.  I assume he will use the R-X bridge measurements to assist in designing a transmitter to antenna matching circuit.  Excellent food for thought !!!!

A question - At ELF, VLF, or for that matter, any frequency where the immediate ground conditions are replied upon to be an integral part of the antenna system, how valuable is a
"flea power" R-X bridge measurement of impedance when 10's or 100's of watts of RF power will be used?  In other words, is the antenna's impedance a constant that is "not" amplitude dependent?

For the "ideal dipole" in free space, definitely the antenna input impedance is amplitude independent.  I can also appreciate for antennas where the ground conditions play an integral part of the antenna system, weather / soil moisture content will indeed effect the antenna's driven impedance.

73 Frank K3DZ / WH2XHA