An antenna is an apparatus that is made out of metal and is used to enhance the sending and/or receiving of radio waves. Antennas are made for AM and FM radios, CB radios, shortwave radio, satellite radio, televisions, networks, GPS systems, mobile phones, radio telescopes, and microphones, for example. Antennas are manufactured for indoor or outdoor purposes. An outside antenna is available for all of these applications, and choosing the best outside antenna for your purposes will probably begin with the purpose for the antenna.
The process of choosing the best outside antenna is different depending on the purpose. For example, in the case of choosing the best outside antenna for a radio telescope, you may well be looking at choosing the best components and building the antenna yourself. On the opposite end of the spectrum, the outside antenna for satellite television service — a satellite dish — is likely to be supplied by the service that you have chosen, so choosing the service in effect chooses the antenna. Choosing a mobile CB radio antenna, on the other hand, brings up a different set of questions about its appropriateness for the particular model of CB radio and how it can attach to the vehicle. When choosing an outside antenna for television, using an antenna map can be very helpful in finding the best choice and the best way to orient it.
For an outside antenna that will be mounted on a building, a unique set of concerns must be taken into account from the outset, and these are restrictive laws or regulations. To keep these in check, the Federal Communications Commission (FCC) in 1996 instituted an Over-The-Air Reception Devices Rule (OTARD) that seeks to limit restrictions on an end-user’s ability to install an outside antenna for television, broadband radio, and direct satellite broadcasts. The rule was updated in 2000, and there are other rules relating to other types of antennas. This rule applies to dish antennas that are 39.37 in (1 m) or less in diameter — or any dish in Alaska; wireless antennas less than 39.37 in (1 m) or less in diameter or measured diagonally; and television antennas for local broadcast that extend 12 ft (3.66 m) or less above the roofline. All antennas outside this scope, as well as antennas that extend into common areas on multiple dwelling units, can be constricted by local ordinances and communities, but restrictions are sometimes allowed by the FCC even on antennas within the scope if there are special considerations.
When zoning ordinances address antennas, they will often restrict an outside antenna for safety considerations, for general appearance, and for compatibility with land use in the vicinity. Covenants, such as those of condominium associations, and historic preservation agreements are two other types of documents that may impact choosing the best outside antenna.