Experimental study on the variability of site shielding factor on trans-horizon radio link

One very effective method of reducing interfering signal levels is to shield the receiving antenna from the interfering source using an obstacle, e.g. a building. For non-uniformly distributed fields a problem arises in determining the shielding effectiveness of an obstacle. In the line-of-sight case, the signal level received in the radio shadow can be determined by using diffraction theory techniques. The shielding of the obstacle can be described by the diffraction loss. A 50 km link, operating at 11.2 GHz, has been established over the Bristol Channel in the United Kingdom. The initial results from monitoring the signal level on the radio link for 12 consecutive months are discussed