Someone inquired about radials and I don't recall who it was. The subject
pertained to elevated vs. buried, etc.
Please refer to IEEE TRANSACTIONS ON BROADCASTING, VOL. 39, NO. 2, JUNE 1993.
The article is entitled, "Using elevated radials in conjunction with
deteriorated buried-radial ground systems." Someone sent it to me, maybe Al
Christman (Oak Grove College), who is one of the four authors.
The essence is that four elevated 1/4 wave radials added to the ground system
actually improved system. The radials were 1/4 wavelength and elevated 10
meters. To do this, they came up sharply from the base. These systems are for
the AM broadcast band.
One of our 160 mtr verticals was tested for this very reason. The tests were
using our linear loaded vertical (about 55') and began at 4' above ground and
progressed to 24' in 4' increments. The antenna base and both radials were at
each test height. Measurements were made using a network analyzer at the
feedpoint and (doing this part from memory) an instrument to measure field
currents. The conclusion was that increasing higher than 16' showed negligible
improvement. This tracks fairly well with the 10 meter height (at AM broadcast)
for the elevated conclusion from the IEEE models. Moxon's suggestion to make
the
two radials a little short and use a common inductor to resonate them (and
equalize the currents) was also done and was effective.
Hope this helps!
73, Tom, N6BT
Force 12 Antennas and Systems
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