Topband: Fw: FCP model
w8ji at w8ji.com
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.
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