Topband: Inverted L Dimensions

[K4SAV]

KJ4FDV: "Sounds great if the ground resistance stays the same for a 
given ground system with different antenna lengths.  But that is an 
assumption." ....

KJ4FDV: "I will lengthen my inverted L to 3/8 wl and  measure the 
feedpoint resistance, subtracting the modeled 52 ohm radiation
resistance to get ground resistance. " ....

That may get you a ground resistance as seen from the feedpoint, but it 
won't get you the ground loss because, as you noted, the current maximum 
moves further out the radials.  Approximating the ground loss as a 
resistor at the feedpoint seems to work fairly well for short antennas 
but not for antennas over 1/4 wavelength.  It does work OK for 
calculating the feedpoint impedance but not for calculating power loss.

Remember you can't get the radiation resistance (or the gain or the 
impedance) of an inverted L using a Mininec ground because there will be 
a low horizontal wire above this ground which will contribute error.

To compound those problems, many people with a lot of modeling 
experience believe that NEC (both NEC2 and NEC4) underestimates near 
field ground loss for very low wires.

Jerry, K4SAV