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[quote=12vman]Is a 120 radial grounding system “Legal”? Or, Would this make the antenna system too efficient? (Beyond the allowed field strength)[/quote]
Here is some background information from which people can make their own judgments.
Part 15 AM does not define or limit the r-f ground itself — only that the length of the conductor(s) connecting the tx system to an r-f ground, together with the lengths of the actual “antenna,” and the wire connecting the antenna to the tx cannot exceed 3 meters.
By definition and the principles of physics, an r-f ground does not radiate. Anything that does radiate r-f is an antenna, or part of one.
A conductor leading from a buried r-f ground through space and connecting directly (or with a short “ground lead”) to a Part 15 AM tx chassis does radiate, because r-f current is flowing through it between the r-f ground and the tx chassis. The flow of r-f current through a conductor sets up radiation. In fact, that is the prime requisite of an antenna.
For a given r-f current through a conductor up to about 5/8-wave long, the longer that conductor, the greater the radiated field it produces. This is why the FCC limited the Part 15 AM radiator length in the first place.
And this also is why “elevated” Part 15 AM tx systems perform better than those installed at ground level, where the total length of the radiating conductors is 3 meters or less.