Guy Olinger wrote:
I find it curious that some of those that so insist on
standing-man-with-meter in affairs regarding performance of antennas are
willing to accept a considerable logical reach on "upward launching" of
ground wave without the appropriate metric **at altitude**. ... But I got
no proof, no measurements, no RBN, no ad-hoc reasonable comparisons.
It should be noted that no research or data is available to support the
theory that currents carried by buried radial wires propagate off the open
ends of those wires to travel through the earth, and produce the
"standing-man-with-meter" groundwave field measured miles away from a
vertical monopole.
Also it should be noted that base-insulated/driven vertical monopoles using
elevated radial systems having no physical contact with the earth can
produce the same groundwave fields as if 120 x 1/4-wave buried radials were
used in place of the elevated radials. How would such remote earth currents
be present when using elevated radials having no contact with the earth?
As to the absence of measured data stated in the quote above, below with his
permission is a quote from a broadcast consultant acquaintance of mine who
has made helicopter measurements of the elevation
patterns of MW monopoles. These data below were taken using a helicopter at
a horizontal distance of 2.8 km from the monopole, showing the fields
existing at elevation angles of zero to about 3 degrees above the horizontal
plane.
This path length is short enough so that earth conductivity has little
bearing on the measured fields, but not so short that the intrinsic,
~cosine-shaped elevation pattern of a 1/4-wave monopole will significantly
affect the fields at those measured elevations.
It will be seen from the data that no "notch" exists in the fields radiated
by the monopole at elevation angles of 3 degrees and less, as expected by
some when considering only the far-field patterns shown by MoM (NEC)
software, and in antenna textbooks.
That low-angle radiation can reach the ionosphere to produce a skywave,
under the right conditions. That skywave can be very useful to hams
using vertical monopoles, even though its existence may not be
recognized.
QUOTE
Helicopter Vertical Calibration
To check for variations in field intensity due to elevation above ground, we
hovered over one location and rose from the ground at 50-foot intervals to
500 feet. Location #12 on the 230° radial was used (non-directional mode),
and the data as presented below shows no significant effect. Measurements
taken for this report were done at an average elevation of 500 feet and the
calibration of the meter takes the vertical factor into account.
Height above ground Field Intensity Variation from 0 feet
0 56 mV/m (Ref.)
50 56 +0.0 mV/m
100 56 +0.0
150 55 -1.0
200 55 -1.0
250 55 -1.0
300 55 -1.0
350 54 -2.0
400 54 -2.0
450 54 -2.0
500 54 -2.0
Averages: 54.91 mV/m -1.09 mV/m (-1.99%)
END QUOTE
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