Anomalous propagation on v.h.f. radio links in the united kingdom

An analysis of v.h.f. measurements made on 65 overland links up to 400 km in length has shown that the field strengths exceeded for about 1% of the time in band III (150¿250 MHz) are greater than previously predicted. The enhancement of band III signals relative to band I (41¿68 MHz) on an adjacent, similar path sometimes reaches 40 dB when a layer of large gradient in refractive index is situated at a height of about 0.5¿0.6 km