>> How can I estimate Rrad for a 100m wire at 10 m average height on 8.3 kHz? 


1579 ohms * (10 m / 36145 m) = 121 microohms

 

Joe, if you wanted you could almost copy Stefan's VLF coil described on his website, using thin enameled wire on a large water barrel.

Assuming your antenna can withstand 28 kV rms, you could run 0.8 A which would instantly put you into the TA playground with Paul.

 

73, Markus

 

PS. 20 dB more will get you 10 times as far (at least in free space ;-)