A radio scanner is a device that allows you to listen in on numerous frequencies and thereby pick up a number of different conversations.
A scanner – which can also be referred to as a police scanner – is a device that allows you to tune or scan more than one discrete frequencies and then to stop when it finds a signal. Typically, a police scanner will allow a person to listen in on everything from conventional radio stations, to two-way radio systems (walkie-talkies).
How Police Scanners Work
Of course, most people will understand how walkie-talkies work. These use a shared frequency band to communicate, meaning that they listen for certain oscillations in electromagnetic energy waves that can be used in order to store and decompress audio.
When a transmitter sends out a signal, it does so by convenient electrical currents into waves – a form of electromagnetic radiation with a wavelength higher than infrared light. Radio waves can have frequencies ranging from as low as 30Hz to 3000GHz. This spectrum is then divided into numerous ‘bands’ which serve as channels – allowing users to communicate without interference. A police scanner – including digital police scanners – works by tuning in to these different bands across a large subsection of the spectrum.
When radio waves hit an electrical conductor, the oscillating fields incur an alternating current in said conductor by pushing electrons back and forth and generating movement, and from here the information can be extracted.
To listen in on specific channels, a bandpass filter is used to separate the particular band from all the other signals being picked up – and this one is then amplified. It is this that will allow a police scanner to listen in on numerous different channels.
Conventional Vs Trunked Radio Systems
This is the process of picking up conventional radios. Using police scanners to listen to trunked radio systems is slightly different. The limitation of conventional radio systems when using them for applications such as business two-way radio, is messages between large groups on a single band can end up ‘queued’.
Trunked radios work by allowing a group to speak on numerous different channels, thereby preventing conflicts and jams. This makes listening to a conversation considerably more challenging using a scanner – though it can be done.
For conventional radio however, scanners are simple and easy to use!
Using a Police Scanner
So how do you start using a police scanner to listen to all those handheld two-way radio conversations out there?
Generally, you will sit and listen in on different frequencies. You can either sift through these frequencies manually, or you can look online to find local frequencies. These might include police radios, which is a fun way to monitor crime in your area – and is perfectly legal in almost all states.
Keep in mind that there is a huge spectrum of frequencies and most of them are going to be empty to begin with – so don’t be surprised if all you hear is white noise at first! Keep on searching and you might surprise yourself with what you find.
- How Amateur Radio Call Signs Work
- How Push-To-Talk Radios Work
- History of the HAM Radio
- Conventional vs Trunked Radios
- What is an AM RF Junction Box
- What is an Arc Gap for AM Antenna Systems
- How to Repair a Field Intensity Meter
- How to Clean an AM Radio Coil
- What is the Internet Radio Linking Project (IRLP)?