Topband: Fwd: radals fer 160m vertcal

[Richard Fry]

Carl KM1H wrote:
> There have been several reports of established AM stations that the FCC 
> gave permission to replace a decayed or destroyed inground radial system 
> with elevated radials or an elevated mesh/radial arrangement.
>
> In all the cases I read the FS measurements exceed the original and power 
> had to be reduced to the original level.

The FCC requires minimum "efficiencies" for the radiators of various classes 
of licensed AM broadcast stations, expressed as the r.m.s. field intensity 
of the ground wave produced at 1 km for 1 kW of power applied to the antenna 
system.  The FCC doesn't have an upper limit for AM broadcast field 
intensities except when a directional radiation pattern is required.

For an example of the non-directional case, there are stations licensed for 
1 kW on 1400 kHz that use 1/2-wave monopoles instead of 1/4-wave (or 
shorter) monopoles.  Such stations using 1/2-wave monopoles still use 1 kW 
transmitters, produce higher fields at all distances, and have larger useful 
groundwave coverage areas than those using 1/4-wave and shorter monopoles. 
This is all perfectly legal.