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Instructions
Calculating Total Loss
Visit an online database of coaxial cable losses at various signal frequencies. See Resources for a direct link.
Locate the column for the model number of the coaxial cable used by the antenna, e.g., "RG-174," "RG-6," "RF-9914," etc.
Scan down the column from step 2 until you reach the cell for the signal's frequency. The labels for each frequency row can be found in the far left column and are measured in megahertz (MHz). The value in this cell represents the decibel (dB) loss per 100 feet of cable for that particular signal frequency.
Divide the total length of the transmission's system cable (in feet) by 100.
Multiply the result from step 3 by the result from step 4 to determine the loss caused by the entire cable.
Take the standard logarithm (i.e., log base 10) of the power output from the transmitter, in watts. This is the level of electrical power entering the coaxial cable.
Multiply the result from step 6 by 10. This gives you the TPO for the system, in decibels (dB).
Add the antenna's gain, in decibels, to the result from step 7. Note: see the antenna
Subtract the coaxial cable decibel loss (from step 5) from the result from step 8. This will give you the effective radiated power of the system in decibels.
Divide the result from step 9 by 10.
Take the inverse standard logarithm (i.e., log^-1) of the result from step 10. This will convert the ERP's units from decibels to watts.
manufacturer's website for antenna gain data in the "Technical Specifications" section.