Several Topander have contacted me that they did not have easy access by
navigating the web site so here is the direct link to the FCC's FS
calculator.
http://www.fcc.gov/fcc-bin/fig8
Additonally the results of the plug in values that read a negative -dbm
are amounts below the theoretical standard of a 1/4 wave vertical, 120
radials, averaging 1/4 lambda.
As shown in the chart below the 1/4 wave standard has 120 radials and
produces 191.382 mV/m @ 1 mile. My point here is that measurements at 1
mile of your 1800 kHz transmission with 1 KW into whatever you have and
using a good FSM can remove a lot of doubt when compared with the
theoretical and/or corrected values.
The Inverse Distance Fields calculated here are in units of mV/m at 1
MILE .
Frequency: 1700.00 kHz
Number of Radials: 120 radials
Correction for number of radials: 0.0000 mV/m @ 1 MILE
Average Length of Ground Radials: 45.720 meters
150.000 feet
0.259 wavelengths
93.333 degrees
Correction factor for length: 0.0000 mV/m @ 1 Mile
Wavelength: 176.349 meters
578.571 feet
Tower Height: 45.720 meters
150.000 feet
0.259 wavelengths
93.333 degrees
Predicted Field Strength from Figure 8, Section 73.190:
(Metric units)
Theoretical Field Corrected Field
At 1.00 kW: 307.999 307.999 mV/m @ 1 KILOMETER
At 1.00 kW: 307.999 307.999 mV/m @ 1 KILOMETER
(English units)
Theoretical Field Corrected Field
At 1.00 kW: 191.382 191.382 mV/m @ 1 MILE
At 1.00 kW: 191.382 191.382 mV/m @ 1 MILE
Hope this information is helpful in the evaluation efforts of your
topband vertical antenna system.
Herb Schoenbohm, KV4FZ
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