... Simply put, the Newburgh area is at least a difficult area and at
worst an entirely inappropriate area to test this thesis. ...
Some may not be aware of the methodology used to determine the FCC
"efficiency" of an AM broadcast radiator (see
http://www.gpo.gov/fdsys/pkg/CFR-2012-title47-vol4/xml/CFR-2012-title47-vol4-sec73-186.xml )
.
Here is another case from that same engineering paper by Clarence Beverage.
I believe this system is still in operation.
\\ The first permanent use of an elevated radial ground system appears to be
at WPCI, 1490 kHz in Greenville, South Carolina. This installation, designed
by William A. Culpepper, involved replacing a standard buried system with a
four wire elevated system consisting of #10 solid copper wire, one quarter
wave in length, and supported on treated wooden posts which keep the radials
4.9 meters above ground. The antenna radiation efficiency, based on field
strength readings on the eight cardinal radials, was 302 mV/m at 1 kilometer
versus the predicted FCC value of 307 mV/m. The WPCI installation was unique
in that the tower was base insulated but the radials came right up to the
tower, 4.9 meters above ground and terminated in insulators. The tower was
fed from the tuning unit, through a piece of
coax to the 5 meter point on the tower where the center conductor of the
coax was attached to the tower and the shield to the elevated radials. This
feed system resulted in a higher feed resistance than would normally be
expected. Data on this facility was taken from the FCC files. //
Note that the elevated radials replaced a buried radial ground system. The
tower was/is 1/4-wave in height, which with a conventional set of 120 x
1/4-wave buried radials would have an FCC 'efficiency" of about 307 mV/m at
1 km for 1 kW of applied power. This system produced 302 mV/m for those
conditions, using four elevated wires as a counterpoise.
R. Fry
_________________
Topband Reflector Archives - http://www.contesting.com/_topband
|