The details of colors used for radio signal propagation maps with their associated signal levels have been explained here. The colors gradient used is based according to the natural color spectrum of the visible light.

The colors specified in the coverage maps represent the radio signal levels as:

• Signal level above 75 dBµV/m (>75 dBµV/m): In this level (or area covered), the radio receiver (at the ground level) is able to easily tune in to the specific frequency with highest clarity and with no any interference from any of other radio broadcasts. A simplest radio set can be tuned in this signal level.

• Signal level above 62 dBµV/m (>62 dBµV/m, < 75 dBµV/m): In this level (or area covered), the radio receiver (at the ground level) is able to easily tune in to the specific frequency with almost no static noise and interference from other radio broadcasts. Comfortably tunable on all properly functioning types and quality of FM radio receivers.

• Signal level above 50 dBµV/m (>50 dBµV/m, <62 dBµV/m): In this level (or the area covered), the radio receiver (at the ground level) is able to tune in to the specific frequency with some static noise and a little interference from other radio broadcasts. All types and quality of receivers are able to be comfortably listened to in this level.

• Signal level above 30 dBµV/m (>30 dBµV/m, <50 dBµV/m): In this level (or the area covered), only the radios with high sensitivity are able to pick the signals of the specific frequency at ground level (typically higher quality radio receivers). An additional external antenna (at some height) or the placement of the radio at some height (2^nd/3^rd floor) is required for reception of signals by poorer quality radio sets at this level. The signals at this level will have some static noise and some interference from other radio broadcasts.

• Signal level below 30dBµV/m (>18dBµV/m, <30dBµV/m): This level is highly affected by the atmospheric and terrain conditions and hence is very weak. This level is also unreliable range in terms radio signal transmission. The signal in this range is easily absorbed by humidity, highly refracted by the atmospheric layers and even enhanced by temperature variations in the path of its transmission. Under certain circumstances, some areas that lie in this signal range have been found to have quite good signal reception by general radio sets.

Due to the properties of the FM signals, sometimes, the signal will reach far away from the predicted areas and sometimes fall far beyond the estimated levels. It is possible to listen to the radio station at this level but generally only in isolated pockets of an area and with an assisted antenna and higher quality radio receiver.

What is Version 1, Version 2 and Version 3 for radio signal maps?

• Version 1: The first colors used for the signal levels were red, green and yellow for 3 level maps with additional light blue and dark blue colors for 5 levels.

• Version 2: With the second version of the coverage maps, the colors used for the representation of radio signals were revised. Here, green and yellow were interchanged to match the internationally used color system. The colors used were increased to display 11 signal/color levels.

• Version 3: The third version of the radio propagation maps utilize the same color scheme as in version 2 and hence are almost identical to the radio maps in version 2. However, version 3 maps do include the essential technical details of the radio transmitter system which was previously not included in version 1 or 2.