Riverside, CA local VHF Police - Digital Noise Burst Sound

[eng4hire]

In Riverside, CA the local city police are on a simple VHF (460's) radio system. When the street units key or unkey their mikes you can hear a very fast very short burst of what sounds like digital data. The dispatch does not emit this sound when they key their mikes. Does anyone know what this is and how to decode it? Whats in the burst?

Dave

 

[FPO703]

The only people who can decode that 'data burst' are the dispatchers. The 'data burst' is the Radio Identifier. If someone hits the 'emergency' button on the radio, it will send that data burst several times until the unit is reset.

There is further detailed data on this available elsewhere in the message forums on here.

 

[nmfire10]

Like he said, it is the 4 digit ID # of the radio and it is displayed on the dispatch console. The PC based consoles can also show a name Alias with the number. Some mobile and portable radio can also decode and dispay these ID's as well. It could be either Motorola MDC, GE Star, or Kenwood Fleetsync. They all sound somewhat similar and do the same thing.

When a unit presses the emergency button, it sends an emergency signal, not just the ID. The console will decode it as an emergency ID and show it as such so the dispatcher knows the unit is in trouble (like a silent panic). It will continue sending the emergency ID every few seconds until one of the following takes place:

1. The console sends an acknoledge data burst telling the raido the alarm was received and it can stop now.

2. The retry counter on the radio expires. They can be set to send the emergency ID any number of times before giving up or be infinate until acknoleged or reset.

3. The user must reset the radio by pressing the PTT, pressing the emergency button again, or turning it off and back on. Unless programmed otherwise, the radios speaker and microphone are muted after pressing the emergency button (hence the "silent panic" thing).

 

[eyes00only]

Probably makes no difference, but I always thought 460's were UHF !

Jerry :roll:

 

[pacrat551]

You can click here for Digital mode samples to see if you can match what you are hearing.