A multiband receiver is a radio capable of receiving a wide range of radio frequencies. Common types are scanners, shortwave radios, and ham radio transceivers. Most are designed to receive transmissions covering only a limited segment of the radio frequency spectrum, while others are capable of bringing in most wavelengths.
A multiband scanner is a multiband receiver designed to monitor the radio frequencies used by police, fire, emergency responders, ships, and aircraft. Portable and desktop scanners can be tuned to receive specific channels or can be allowed to search for the closest active band. These scanners can receive radio transmissions 24 hours a day.
A shortwave radio is a specialized multiband receiver designed to pick up only those stations broadcasting over a specific range of frequencies. Some models may only be designed to receive shortwave broadcasts from nearby stations. Most are equipped to receive seven bands, providing access to global shortwave broadcasts. Shortwave reception is influenced both by the time of day and by atmospheric conditions. All stations are not available 24 hours a day.
A ham radio is a specialized multiband receiver. It can receive on the same bands reserved as scanners and shortwave receivers. While other multiband radios have only the ability to receive, a ham radio enables a licensed operator to transmit as well. Transmissions are possible only on dedicated bands determined by law. Reception varies according to atmospheric conditions and the time of year.
While a multiband receiver is usually designed to bring in only shortwave or ham, some have the ability to cover most of the broadcast spectrum. In addition to shortwave, emergency, aviation, and marine bands, a multiband radio may also be able to pick up AM and FM radio stations and the audio portion of television broadcasts. Designated emergency radios for home use usually cover police and fire bands, two or three regional shortwave bands, and local AM and FM stations.
A multiband receiver can be either portable or mounted on a desk or table. Portable multiband scanners and shortwave radios are often small enough to be handheld, and are powered by internal batteries. Their range of reception is often limited. A desktop multiband radio is more permanently installed and is plugged into a power outlet in a wall. This type of multiband receiver is more powerful and has better reception of distant stations.
Multiband radios are usually equipped with telescoping antennas that slide down or fold up when the receiver is not in use. Installing a more sophisticated antenna can often improve reception.