UHF Radio System

NOTE: frequency information has been removed at Northumbria Police's request.

Often referred to as PR system (Personal Radio). This provides localised coverage for individual police stations. Each radio channel may cover an area the size of a small town and be shared by usually one main station and a number of sub stations.

The hand held walkie talkies that you see officers using operate on the UHF system. UHF is used because it gives good coverage in built up areas and the radios, and especially their aerials, can be quite small due to the very short wavelength. Hand held radios typically only transmit at half to one watt, but this is perfectly adequate as repeaters rebroadcast this signal at a higher power from strategic locations such as the top of a tower block. By operating at such low power, radios will draw less power from their batteries and thus have longer operating times between charges.

Encryption

One of the main differences between the VHF and UHF channels is the use of encryption. In the mid nineties, police forces up and down the country spent vast amounts of money on encrypting their communications. A lot of bad press had been received about people using scanners to listen in on police channels. I think a big influence in encouraging the use of encryption was the Diana gate affair, when a telephone conversation Princess Diana was making on her mobile phone was taped by a "radio amateur" using a scanner.

Gradually sophisticated encryption was introduced on police channels and now virtually every UHF channel has the capability to be encrypted, although they often are not for various reasons explained on my encryption page! I have no doubt that Northumbria Police would have liked to encrypt their VHF main set channels, and I have even heard trials being conducted. However, this has not taken place, probably due to the VHF channels using AM modulation which probably makes the encryption more prone to interference than on the UHF channels.

I have devoted an entire page to the business of Northumbria Police's encryption system. You can read all about it by clicking here.

Another difference is that talkthrough is usually enabled on the UHF channels. This allows officers to speak direct to each other without having to go via the channel operator. I have heard occasions where it has been switched off, usually if a channel is receiving heavy interference.

There are a number of what are termed "back to back" or simplex channels available at UHF. A good example of this is channel REMOVED which is the Air to Ground channel. If an incident requires the support of the police helicopter(India 99) or plane (India 88), it is often the case that you will hear officers involved being told to switch their radios to channel REMOVED. This allows them to talk to each other and to the aircraft without clogging up the normal PR channel which needs to remain clear for other incidents. When talking on channel REMOVED officers can communicate with other officers over a range of about half a mile, however when talking direct to the aircraft this range increases dramatically due to the height at which the aircraft is operating.

CID Channels

CID officers can be recognised by the callsign Zulu. However you are very unlikely to pick them up on your scanner as they were one of the first get encryption. You may sometimes hear them on a normal channel asking for assistance though. When on special ops i.e drugs raids, obo's etc. they use a special channel specific to that operation. These channels are usually at the lower end of REMOVED MHz e.g. REMOVED, REMOVED. At one time these channels were in the clear but nowadays they are always encrypted. The channels usually make use of a repeater to extend communication range, but sometimes simplex channels are used. Bear in mind that for special ops police may make use of frequencies outside of their normal REMOVED MHz allocation. Short term hire frequencies might be a good place to look! Extensive use is also made of mobile phones for non urgent communications.