Transmission Loss - Coverage Interpretation

The coverage plot produced shows the loss between a centrally located transmitter (or receiver) and points on the ground out from that station.  The loss is computed using the Free Space Loss calculation from Recommendation ITU-R P.525-2 equations 2.2 to which is added a simple knife-edge diffraction loss calculation to yield a basic transmission loss.

The coloured scale is automatically ranged with high values shaded red and low values blue.  The units are reported in db relative to isotropic antennas placed at both ends of the link.

The plot can be used as a coverage assessment by computing off- line the maximum transmission loss tolerable in any communications link.  In a broadcast case this would be the maximum loss between the transmitter (plus or minus any gains or losses in feeders and antennas) and the receiver (again plus or minus any gains and losses from the receive antenna system).  A transmitter output power of 60dBm and a receiver sensitivity of - 80dBm would yield a 60-(-80) or 140dB basic transmission loss.

Simple knife edge diffraction is generally considered overly optimistic in most terrain types and therefore the prediction could be considered to be optimistic.  It is however useful in that it provides a quick indication of the coverage achievable around a site.  For more accurate methods see the other products on this site.