Beginners guide to radio scanners
Most radios you encounter in everyday life have a single purpose, for example the radio you have in your car is designed to receive only commercial radio stations. Radio scanners, on the other hand, can receive signals transmitted at a wide range of frequencies, allowing users to listen in on a variety of different communications including air traffic control, emergency services (police, ambulance and fire), hobbyists (Citizens Band), race teams, astronauts ...and so on. Furthermore, radio scanners contain microprocessors, which enable them to automatically detect when a transmission is occuring on a particular frequency. This ensures you never miss out on the action.
Whereas the frequency coverage and range of features that your scanner is equipped with depends on the price you pay, there are some things that all radio scanners have in common. For example, virtually all scanners have search and scan modes as well as a squelch control.
Search mode is used to detect any active frequencies within a given frequency range in your area. The scanner will automatically search through the frequencies until a transmission is found, at which point it stops. You can then store the frequency in the scanner for future reference. Some scanners, for example the Yupiteru MVT-9000 MKII, have an auto-store function. This Yupiteru model can be left unattended whilst it stores up to 50 active frequencies in a specified memory bank. The search speed, which is measured in steps per second, varies between models.
Scan mode: Once you have some frequencies stored within your scanners memory banks, you can search through them for activity. Some radio scanners come with a number of preprogrammed frequencies. Scan speed is measured in memory channels per second.
Squelch control: This adjustable control is used to reduce static when a station is not active.
Active frequencies are stored in memory channels, which are organised into memory banks. This allows you to store frequencies of a particular type (e.g. air traffic control) together. The number of memory channels generally varies between about 100 and 1000, however the Alinco DJ-X2000 has a massive (and probably slightly excessive) 2000 channels.