Television & Radio Hardware - Poles and Masts
Most installations of an aerial or two will use a pole.
There are two options; a straight pole or a cranked pole (a cranked pole has a bend in it which allows the top to offset the aerial). The cranked pole is usually used to work around overhangs of roofs, rather than having large stand-off brackets to get the pole out far enough from the surface being attached to. Most average houses will use a straight pole and standard brackets.
The diameter of the pole and thickness of the metal is vitally important, with larger wind loadings requiring thicker, and therefore stronger, poles. Poles can be made of aluminium alloy or steel, with steel poles tending to be stronger at thinner gauges.
For the tallest of installations, masts can be used. These utilise guy wires (the same principle that many large transmitters use) to keep the large pole upright. However, careful planning is needed to ensure the attachments are suitable. Very few installations will require a guyed mast.
Although not necessary, a pole cap is simply a plastic cap which can be placed on the ends of the pole to prevent the ingress of water. This is particularly useful for steel poles which tend to rust from the inside. They also prevent wind noises on the pole to some extent.
There are two cap types; external and internal. The external cap fits over the pole (like a bottle cap) while the internal cap sits on the inside so can not easily been seen. The external type are less durable and tend to break off after some uses due to more exposure, though they are usually more watertight overall.
A pole cap could be added to the bottom though this is not necessary. If one is being added to the bottom, drill a small drainage hole to ensure that any water that does get in can get back out.