Signal strength variations at 2 GHz for three sea paths in the British Channel Islands: Detailed discussion and propagation modeling

Abstract

[1] Signal strength measurements at 2 GHz have recently been made on three over-sea paths in the British Channel Islands. This paper focuses on explaining the propagation characteristics during periods of normal reception and periods of enhanced signal strength with particular emphasis on a 48.5 km transhorizon path between Jersey and Alderney. Evaporation ducting and diffraction appear to be the dominant propagation mechanisms at most times. The influence of the evaporation duct during periods of normal propagation has been confirmed by modeling the over-sea propagation conditions using Paulus-Jeske evaporation duct refractivity profiles as input to the parabolic equation method. During periods of enhanced propagation, which occur approximately 8% of the time on the longest path (48.5 km), the presence of additional higher-altitude ducting/super-refractive structures has been verified and their influence has been modeled with reasonable success.

Signal strength variations at 2 GHz for three sea paths in the British Channel Islands: Observations and statistical analysis

“…The reason for these discrepancies is not currently understood, but these results suggest that ITU-R P154-2 underestimates considerably the amount of interference possible from distant systems using the upper end of the UHF band. The reasons for the behaviour of the data are investigated in the paper accompanying this [Gunashekar et al, 2007]. …”

“…Although it is useful to resolve the significance of air temperature, sea temperature and other meteorological factors on the occurrence of enhanced signal strength, this analysis is reported in the paper accompanying this [Gunashekar et al, 2007]. Here, the analysis is kept to statistics of the regular annual and diurnal variations, so that the data are potentially useful to predict enhancement without recourse to any model or assumption.…”

Propagation Factor and Path Loss Simulation Results for Two Rough Surface Reflection Coefficients Applied to the Microwave Ducting Propagation Over the Sea

“…Nevertheless, propagation calculations and measurements have shown this neutral profile is a good practical approximation to the average behavior of the M (z) [30] and (16) has been widely used as input to propagation modeling under evaporation duct conditions [7,8,14,17,30]. Further discussion on the profile (16) may be found in [9].…”

“…The PE and APM have been extensively validated through simulations and measurements for different complicated environments, including the case of tropospheric ducting propagation, see [6,8,16,26].…”

“…The ducting is present for small percent of time but it seriously influences the radar [3,4] and communications systems [5][6][7][8] working in the microwave range: the rays' bending under ducting differs from that for standard troposphere and provokes erroneous precipitation detection by ground-based meteorological radars, the electromagnetic energy trapping within the ducts leads to trans-horizon signal propagation, reflections from upper refractive layers cause mulipath fading, etc. Depending on the physical mechanism of their formation, the tropospheric ducts are subdivided in different types -here we are interested in evaporation ducts for which the negative gradient of M is due to evaporation from large bodies of water [9].…”