GPS Source, Inc.  FreeSpace Loss Calculator Building is 50' wide at  narrowest area, 100 feet on either side results in a 250' diamter area   
        -140 dBm at 100 feet from the building to meet
NTIA regulations
At 158' pattern from emitting antenna provides a greater than 42' buffer either side   
               

GPS Carrier Frequency
(MHz)
Transmitted Power dBm Range in Feet Free Space loss with Isotropic Antennas Effective Radiated Power dBm @ Range Effective Radiated Power (dBW) @ Range Effective Radiated Power (W)  @ Range
 
Reference Dipole Gain
Range in Miles
Effective Isotropic Radiated Power (dBm) Effective Isotropic Radiated Power (dBW) Effective Isotropic Radiated Power (W)  @ Range
2.15 Transmitted Power W ERP
  Transmitted Power W EIRP Range in Kilometers          
Free space path loss expressed in dB can be determined in terms of distance and frequency

Range in Meters

GPS Carrier Frequency
(MHz)
Transmitted Power dBm Range in Feet Free Space loss with Isotropic Antennas Effective Radiated Power dBm @ Range Effective Radiated Power (dBW) @ Range Effective Radiated Power (W) @ Range
   
 
Reference Dipole Gain
Range in Miles
Effective Isotropic Radiated Power (dBm) Effective Isotropic Radiated Power (dBW) Effective Isotropic Radiated Power (W)
2.15
Range in Kilometers
Transmitted Power W ERP
Transmitted Power W EIRP
Range in Meters