but I am at a loss as to what
additional
information one would need to model a center fed 75 foot long half
wave antenna, resosnant at 6.2 MHz, positioned 15 feet above a flat
metal roof, fed with 100 feet of 50 ohm coax (RG8), and operated on
any one of three frequencies.... 3.95MHz, 5.4MHz, and 7.2 MHz.



Small correction.... the feedline is also not important since all I am
asking for is essentially the feedpoint impedance of this antenna at those
three frequencies of operation.


Ed K7AAT