Silver solders Platinum Cathodic The most obvious problem that arises from corrosion is the possible reduction in mechanical strength of an antenna, and the problems that arise when trying to disassemble an antenna system that is corroded for maintenance. However, there are other effects that can arise. Many antenna elements are made from aluminium. Also most feeders are made from copper and this means that the electrical joints made between the two can corrode, resulting in a high resistance connection that will significantly degrade the performance of the antenna. Another problem that can occur is often called the 'rusty bolt effect'. It occurs because sometimes the corroded materials can act as a semiconductor, producing non-linear component that may generate harmonics and inter- modulation products if very strong signals are present. It is usually more 118 Newnes Guide to Radio and Communications Technology applicable to transmitting stations that carry several transmissions. Here the spurious signals generated may cause interference to other local users. Safety An antenna can be a potentially hazardous item, both in its installation and during its use. Fortunately there are generally few accidents, although there have been fatalities as a result of their use and installation. However, with a little care and common sense it is most unlikely that any accidents will occur. The main requisite to prevent any accidents is a general awareness of safety. Safety precautions take many forms. One of the first is that under no circumstances should an antenna be erected anywhere that it may fall onto power lines, or that power lines could fall onto it. This may seem like a remote possibility, but there have been instances of antennas falling onto power lines. At all times the proper materials and fixings should be used. It is not worth taking short cuts as falling antennas can cause serious injury, not to mention the damage to the antenna and other property. For smaller antennas normal television fixings can often be use