I was in the Merchant Navy in the sixties,sailing on oil tankers. When we entered the Persian Gulf bound for Ras Tannura (Saudi Arabia) for a period of about 30 minutes we could regularly contact Ras T. on VHF,a distance of about 300 miles. The contact was loud and clear but only for around the thirty minute period, a steaming distance of about 8 nautical miles. We then lost contact until the following day when we were about 25 miles away. The Sparks said it was the bounce of the radio waves.