Topband: Modeling "Ground" and losses

[Tom W8JI]

> Not only that, but it defies logic that radials would NOT exhibit the same 
> current and voltage distribution of any other conductor carrying RF 
> current. The boundary condition is near zero at the end ( "near" because 
> of capacitance at the end). Rudy Severns, N6LF, has explored this in his 
> studies of radial systems. Rudy's work includes extensive modeling to 
> understand and document what he was seeing in measurements of carefully 
> constructed experimental systems.

There are only three ways a radial would not exhibit standing waves (waves 
that increase and decrease in level with distance):

1.) The radial is too short to have enough space for a part of the 
wavelength  to stand. An example of this would be trying to measure the 
current difference along a 60-foot wire on 160 meters. It would just 
smoothly taper.

2.) The radial is terminated in the surge impedance of the radial. This 
would be like a transmission line terminated with the correct resistance.

3.) The ground sucks up the current at such a rate that there is not enough 
current left to increase.

All the radials I have measured that are long enough to be over 1/4 wave 
electrical have shown standing waves. The current is less at the base than 
some distance out from the base, and it never seems to have anything 
noticeable to do with radiator height.

I can take a 40M 1/4 wave vertical, surface bury 15-20 radials, and find 
long lengths (beyond 1/4 wave) that make base impedance go to 50 ohms or 
more, and the FS measures the same as other systems that have 35-38 ohm base 
impedance.

Feed impedance doesn't even have to track the efficiency.

73 Tom