Topband: Fw: FCP model

Tom W8JI w8ji at
Thu Aug 2 03:24:00 PDT 2012

Very interesting discussion. Can't we quantify our ground systems by placing 
RF ammeters at the feed point? >>>>>

No, we cannot obtain reliable useful information there. If we want to know 
field strength change, we have to measure field strength change. :-)

It would seem to me that once the current in the ground wire - whether it be 
attached to a ground stake, ground radials, elevated counterpoise, resonant 
radials or whatever - is equal to the radiator current no further 
improvement is possible. >>>>

Current into the ground terminal always equals current into the antenna 
terminal, unless the feedline is radiating or acting as a ground.

The problem is this.....

Feed resistance and feed current tells us nothing about how losses are 
distributed in a system with standing waves.

I can have a fixed radiator and change only ground systems, and have higher 
efficiency with lower feed current or higher feed resistance. The opposite 
can be true, also. This is because measuring something at one point does not 
tell us what is happening at other points in a complex system. We don't know 
what portion is leaving in space or heating the earth, because once out of 
the antenna it is gone.

The only possible way to measure efficiency change is to measure field 

People who measure feedpoint resistance changes while changing radials or 
ground systems and think they know loss changes are just kidding themselves.

73 Tom 

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