MF sky-wave propagation: a comparison of measurements made at sunset and sunrise

The strength of MF skywave signals is greatest at night and weakest during the day. The increase in field strength which occurs at sunset has been extensively studied but less is known about the decrease which occurs at sunrise. A description is given of a series of measurements made by members of the European Broadcasting Union (EBU), which cover both the sunrise and sunset periods. The results show that during the sunset period the measurements agree closely with the existing CCIR curve but that the sunrise measurements indicate that the existing CCIR curve is inaccurate. A modified curve for MF use is proposed