Pro-197 - Trunking Question

[Wthom100]

Hello Everyone -

Just got a new Pro-197 and I'm up and running in the Detroit area on the P25 I MPSCS trunk system - gets lots of traffic to listen to.

I think I may not be understanding some basic information on trunking. In pro-197 I did a direct lower / upper limit search on the 867-868 Mhz frequencies. In the search I got a lot of hits with traffic - "P25" and the radio frequency flashes in the display - I store the frequency using the STOR button - it saves the object in my scan list. The next day while scanning the scan list the frequency comes-up but the sound is garbled (a garbling sound like in tin can - I do not believe the frequency is encrypted because it was very clear the night before) - sometimes other frequencies I stored come-up but have that "buzz-saw" sound.

I read somewhere that trunking systems change control channels on periodic basis - is that what could be happening here? - i.e. the frequency that at one time had clear traffic on it when I stored it somehow changed and is no longer listenable.

Was wondering why this was happening. Thanks

 

[DickH]

2 points.
That system, especially the State Police, has many encrypted talk groups. Some radios
can turn the encryption on and off.

You need only the control channels for each site and each site. If it's trunking correctly you will NEVER hear the control channel (the "buzz saw" sound).