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It will depend on atmospheric conditions. 1.09GHz is mostly line of site, but there is atmospheric refraction and sometimes ducting that will usually extend the range.
There are area specific refraction tables for planning microwave links. The tables have a K factor, which the Earth's radius is increased by to get the expected range (a bigger Earth would have a more distant horizon). Usually the range is extended, but sometimes the refraction will reduce the range, by refracting away from the earth. This is season, weather and area dependent. It can be a real problem for stable long distance microwave links.
The refraction occurs at the boundary between different layers of air. Ducting is refraction within a layer, and is leaky in nature. Ducting is common just above the ocean, where there is a layer where the air is more humid. It has been used in tests of over the horizon microwave links, and in over the horizon radar. For radar, it is one of the reasons why ships mount their radar as high as possible. The radar needs to be above the ducting layer.
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