I've been learning how my new Uniden 396T and trunking works so I've started mapping the VKI digital network. No, sadly, you can't listen in even with a P25 digital capable scanner but you'll learn more about scanning, trunking and grabbing data from the ACMA database.
This Excel spreadsheet contains the digital control channels I've been able to hear here. On the '396 I find them by:
- Setting a custom search scan from 502 to 505MHz, then
Adding the frequencies which appear to be digital - screen says DAT, LNK or ENC - to a temporary new digital system (more about that later)
Set the scanner to scan this new digital system bank
For each digital channel the scanner stops on, hit Hold. If the channel is a control channel, its ID will appear on the top part of the screen, i.e. SID: 01ADh-0110
Now, a bit about trunking. Each control channel controls a site. A site is a control channel plus any number of conversation frequencies. Radios in the VKI network continually scan their list of pre-programmed control channels and select the strongest. They then register with that site and tell the site which channel (technically, a talk group) it's tuned to.
Each time traffic appears on the network for that talk group (say, talk group 5 - which is, say the same area as channel 34 analogue was), the control channel tells the radios registered with it to tune to another frequency at the same site so the conversation can be heard. ("Hey, radios interested in talk group 5, tune to 503.5187MHz now") If no radios are registered at a particular site as being interested in a talk group, then the site doesn't waste resources by setting up a conversation frequency for it.
This all happens dynamically as conversations take place. I don't know if the VKI network does this, but in some trunking systems, if a site runs out of conversation frequencies, the system can even temporarily allocate the control channel for conversations as well.
Ok. So perhaps you're not convinced that VKI is encrypted and you want to try listening in yourself, or maybe you're just insatiably curious...
If we followed the steps above, or seen the spreadsheet, we should have a list of frequencies and site IDs. Now what? On the Uniden, we set up a new system for each site ID. (Menu | Program System | New System | MOT. We then choose P25 for VKI, or 800MHz standard for analogue ) and enter the control frequency we found. Each site has to have its own system, even if they're linked together and carry similar talk groups. If we scan this group of systems, the scanner will listen to the control channel "go to" instructions for each site and tune to the talk groups as they become active. (On VKI, the scanner will give a burst of noise then show ENC - Channel Encrypted
) You're now trunk tracking!
Coming up, using the ACMA database to find the site associated with a frequency.
