The materials for the manufacture of antennas
Separately it is necessary to describe the materials used in the manufacture of the antenna. The antenna elements may be made of tubes, rods, strips or corners of any metal. In accordance with the surface effect of high frequency currents occur exclusively on the surface of metal, so thin-walled tube or a solid rod of the same diameter in its properties exactly the same.
Usually television antennas are made of aluminum or its alloys. This is because the antenna of such tubes is rather strong and lightweight. However, the electrical properties of aluminum antennas is not high enough due to the fact that in the joints of antenna elements often develop bad contacts caused by an oxide film covering the surface of aluminum alloys. This over time can cause the antenna down.
Even worse is when during Assembly of the antenna elements used or tightening bolts of different metals. However, due to the contact potential difference occurs galvanic couple that Deplete the metal at the connection. Therefore, aluminum antenna it is best to connect using gas welding or, in the extreme case, with aluminum coupling bolts, nuts and washers. Before assembling the elements in the joints it is useful to clean up a file and liberally lubricated with petroleum jelly to prevent the formation of oxide film.
In principle, the antenna can be made of any metal; copper, brass, bronze, steel or stainless steel. Compared with aluminum antennas, these antennas are, of course, will be considerably heavier. In all cases the connection of the antenna elements are preferably carried out so as to exclude the possibility of poor contact due to corrosion or destruction from electrolysis. All connections can best be welded or propaivat. In this case, the antenna elements may be formed of different metals. If you used steel elements and propagules using acid flux, to remove its residue solder points should be thoroughly washed with hot water, otherwise flux residues in a short time will lead to severe corrosion of the metal.
It should be remembered that pike only serve to ensure good electrical contact. Mechanical loads soldering tin solder cannot withstand. It is therefore necessary to ensure the strength of the connections in other ways (rivets, bolts, etc.), and then build these connections are soldered. With the exception of soldering, brazing, which have sufficient strength. To prevent corrosion of the antenna after complete Assembly and pripiski to her feeder with a matching unit is thoroughly cleaned of oxides and well stained in several layers of oil or nitro. You can also use synthetic topcoat. These dyes are good electrical insulators and antenna operation no impact. Use the same aluminum paint is undesirable, since they have a finite resistance value.
The connection of the cable to the antenna elements need to be sealed to avoid ingress of moisture. Better sealing is achieved by using plasticized epoxy resin. Such resin epoxy glue marks EAF is available on sale in the shops of household goods. Place subject to sealing, is superimposed on a piece of clay, it is a deepening of the appropriate form and poured resin. After it has cured, the clay is removed and the surface of the resin is processed with a file to give it a smooth shape. For good adhesion of the resin to the metal it needs to be previously degreased with acetone.
According to the book of V. A. Nikitin How to make good TV; Publication: www.cxem.net