On 9/27/2012 4:58 PM, W2XJ wrote:
The other difference is that all this information is based on ground wave
propagation. There is nothing that addresses higher angle sky wave propagation
common for 160 M operation.
More correctly, it is field strength measured close enough to the
antenna to be "stable."
The vertical pattern is primarily shaped by soil conductivity, and is
the result of energy radiated by the antenna being reflected by the
earth in the FAR field of the antenna.That reflection adds to the direct
radiation to form the vertical pattern .The stronger the reflection, the
greater the low angle radiation.
The "ground system," whether a ground screen or radials, is in the NEAR
field, and affects how much power is lost in the earth, how much is left
to get radiated so that it CAN be reflected. In other words, the ground
system primarily affects the overall STRENGH of the signal, but has very
little effect on the shape of the vertical pattern.
73, Jim K9YC
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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