Tropospheric scatter

Tropospheric scatter, also known as troposcatter, is a method of communicating with microwave radio signals over considerable distances – often up to 500 kilometres (310 mi) and further depending on frequency of operation, equipment type, terrain, and climate factors.

[1] Normally, signals in the microwave frequency range travel in straight lines, and so are limited to line-of-sight applications, in which the receiver can be 'seen' by the transmitter.

In spite of this widespread belief, during the war there were numerous incidents in which high-frequency radar signals were able to detect targets at ranges far beyond the theoretical calculations.

[2] In the immediate post-war era, the limitation on television construction was lifted in the United States and millions of sets were sold.

Based on the same calculations used during the war, the Federal Communications Commission (FCC) arranged frequency allocations for the new VHF and UHF channels to avoid interference between stations.

[2] Bell Labs was among the many organizations that began studying this effect, and concluded it was a previously unknown type of reflection off the tropopause.

Although the vast majority of the signal went through the troposphere and on to space, the tiny amount that was reflected was useful if combined with powerful transmitters and very sensitive receivers.

Using Lincoln's powerful microwave transmitters and Bell's sensitive receivers, they built several experimental systems to test a variety of frequencies and weather effects.

The BT systems, based at Scousburgh in the Shetland Islands, Mormond Hill in Aberdeenshire and Row Brow near Scarborough, were capable of transmitting and receiving 156 analogue (4 kHz bandwidth) channels of data and telephony to / from North Sea oil production platforms, using frequency-division multiplexing (FDMX) to combine the channels.

The tropospheric scatter phenomenon has been used to build both civilian and military communication links in a number of parts of the world, including: As well as the permanent networks detailed above, there have been many tactical transportable systems produced by several countries:[20] The U.S. Army and Air Force use tactical tropospheric scatter systems developed by Raytheon for long haul communications.