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Paul,

Your comprehensive development of your antenna system is interesting and informative. Could you describe how you measure the ground resistance of the antenna system?

The system I use is described here:

http://www.part15.us/forum/part15-forums/general-discussion/rf-current-transformer-antenna-tuning

The key to this is the simple RF current transformer which, when placed between the transmitter output and the input to the loading coil, gives a means of measuring the feed point impedance. Resonance is shown by a zero degree phase shift between the V and I and if the coil Q is known the coil resistance can be calculated. From the V and I measurements at resonance the total antenna system resistance can be calculated and the coil resistance subtracted to find the ground+radiation resistance. More details are in the link above.

Neil