Evaluation of prediction accuracy for the Longley-Rice model in the FM and TV bands

Accurate geographical coverage predictions
maps for FM and TV are needed for channel and
frequency allocations and in order to avoid unwanted
interferences. The Longley-Rice model has been used
for this purpose over the last four decades and still
being used almost exclusively by the FCC in the
United States. In this work a comparison is presented
between the relative accuracy of this model in the
VHF-FM and UHF-TV frequency bands. Simulations
were made with accurate and up to date input data
(antenna height, location, gain, transmit power, etc.)
for the FM-TV stations provided by the ERT S.A.
public broadcaster in the region of Thessaloniki –
Greece. Finally, the calculated – simulated results
were confronted to field measurements using a Rohde
& Schwarz FSH3 portable spectrum analyzer and
high precision calibrated biconical and log-periodic
antennas, and the errors between predictions and
measurements were statistically analyzed in the two
frequency bands. It has been found in this study that
the Longley-Rice model, in general, overestimates
field-strength values, but this overestimation is much
higher in the VHF – FM radio band (88-108 MHz)
than in the UHF-TV band (470-790 MHz).