Topband: [Fwd: Field Strength Calculator]

[Herb Schoenbohm]

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