A radiometeorological study, part II. An analysis of VHF field strength variations and refractive index profiles

Abstract

This paper discu sses the cum ulative probability distributions of fi eld strength for four 200 km VHF p at hs in Illin ois in t erm s of a classification of r cfractiv e ind ex profiles. It is shown that exten ded elevated layers produce signal enhance ments of 10 to 25 db a bove the level observed in unstratified conditions. Assuming the layer characteristics given b y rad iosonde data, the bes t agreement between calculated and m easured valu es of fi eld strength is obtained us in g a layer model with a lin ear n-profi le. The possible influ ence of smaller layers is also discussed in relation to the observed r esults for cond itions judged to be unstratified or 'Nell mixed on t he basis of sonde data.

The importance of tilted layers in the tropospheric ducting of radio waves over the Timor sea

“…For a horizontally stratified atmosphere the path length ooe a ray through an elevated layer can be small, but if the layer is tilted upwards away from the transmitter then this path length can be increased so that the ray is refracted back towards the earth's surface. Bean et al [1963] noted that, on VHF radio links over 200 km, tilted elevated layers appear to produce the greatest enhancement of signal strength. They comment that this is probably the result-of focussing effects due to layer tilt or a result of the asymmetry of the path (the transmitting antennas being 200 m above the ground and the receiving antennas, 30 m), but the more likely cause appears to be that proposed above.…”

U.S.A. National Committee Report, Fifteenth URSI General Assembly, Munich, September 1966: Commission 2, Radio Propagation in Nonionized Media; Progress in Radio Propagation in Nonionized Media

“…Radiometeorological study of 200-km fields was made by Bean, Frank, and Lane [1963], from which they concluded that radiosonde data could be fit best with a linear n-profile layer model. Wait [1964b], however, pointed out a defect in the reflection coefficient formula used.…”

Comparison of Surface Radio Refractivity Variability in the Northern and Southern Parts of Quebec, Canada

“…Other metrics are used to evaluate the quality of the propagation, including refractivity gradient d N in the first 1 km above the surface (Bean et al, 1963; Lane & Bean, 1963; Valma et al, 2011) and the equivalent gradient G e (Misme, 1960). Authors in Valma et al (2011) studied the variations of radio refractivity and its vertical gradient in Lithuania, they found that the radio refractivity and its vertical gradient could change as the weather suddenly becomes significantly colder.…”