Radio Scanners

[alvinc]

Quote:

Originally Posted by Route 66 Have y'all found that police agency's are scrambling their transmissions?

Quick answer: not much encryption, but lots of trunking systems.

Details:

Many public agencies in the US are moving toward trunking radio systems. These are digital radio systems where there are a set of radio frequencies with one or more of them being control frequencies that direct the conversations. This allows the personnel to have multiple conversations going on at one time without the people having to coordinate what frequencies to use.

The side effect of the trunking system is that a normal scanner will not be able to follow a conversation because it may be moving around to different frequencies. Even if there is only one conversation going on the scanner will often miss bits and pieces of the conversation as it search for the next busy channel.

There are scanners that have trunk tracking capability, but they still need to be programmed for the the specific trunking system they are monitoring. Setting this up while traveling down the highway would have to be done by a passenger, and will require prior knowledge of the frequencies in the trunk. Not impossible, but difficult.

As you can imagine frequency shifting is a form of obfuscation (encryption is really anything to confuse or hinder intelligibility of something). As to whether many are using encryption of the actual data signal, some of the equipment is capable of this.

After I typed this in I looked on Wikipedia and they have a better description: http://en.wikipedia.org/wiki/Trunked_radio_system

This link is to one of the Motorola systems that supports encryption:
http://en.wikipedia.org/wiki/Motorola_Type_II_SmartZone

There are lots of links in the Wikipedia pages above for other aspects of agency communications.

Also take a look at a US Department of Justice web page:
http://www.ojp.usdoj.gov/nij/topics/...encryption.htm

[John-D]

Many agencies in Michigan went to 800 MHZ trunking systems, and the FCC discourages sale of hardware to intercept those transmissions, (Though you can buy the receivers no problem)

Personally.. after 8 hours a day by 5 days a week for 25 years of listening to police radio traffic (When I was not generating it that is) the very last thing I want to hear is POLICE radio

Though I do admit, it was fun getting payed to tell 'em where to go

(It is more fun getting paid and NOT having to tell 'em anything except where to send the check!)