Several contractors and fire marshals have asked if there is a way to predict indoor coverage before a building is built or improvements are made. There are several modeling tools that can be utilized, however, it is important to remember that coverage predictions are estimates and are only as accurate as the information being used to define the variables. RF signals are subjected to a wide variety of obstacles and varying geographic and atmospheric conditions as it traverses a path from the radio site to the recipient. In the end – the only way to accurately assess radio coverage is to make physical measurements.
As a community service, RFSignalman recently tested the 800MHz radio coverage in the Elk Grove, CA. The dots, on the following Google Map, are color coded to reflect a range of signal levels. You can also zoom in and click on each dot to view the actual level measured at that point. The outdoor measurement eliminates many of the variables and provides a good benchmark in estimating the amount of loss that can be introduced by your building before reaching the minimum acceptable level of -95dBm.
Outdoor Signal Level up to:
-70dBm = Green (Good – allows the building owner minimum of 25dB for building loss)
-80dBm = Yellow (Good/Marginal – allows the building owner 15-24dB of building loss)
-90dBm = Red (Marginal/Bad – allows the building owner 5-15dB of building loss)
-95dBm – Light Blue (Bad – allows the building owner less than 5dB of building loss)
-100dBm – Blue (Bad)
The measurments should not be considered a pass/fail indication, since every building is a little different, but it provides a good overview of outdoor radio coverage in Elk Grove and geographic areas that could potentially have issues with indoor coverage.