WA Radio Scanner Users' Group

Hi Folks.

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

These instructions are good for the analogue systems up at 865MHz, too. On analogue trunking, the control channel sounds like a sharp rumbling noise, and it will come up with the SID as well. (Not all data carriers on 800MHz are trunking... if a SID doesn't appear, it's not a Motorola network - move on)

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.

Hey Gav,

Good post, unfortunately I don't have a trunk tracker scanner. The post was very intersting but the picture below probably describes it the best way possible

Bonez wrote:Hey Gav,

Good post, unfortunately I don't have a trunk tracker scanner. The post was very intersting but the picture below probably describes it the best way possible

I've got one for sale Blake - UBC780XLT!

Cheers, CC

Just curious Gav, do you actually hear anything at all, or does it just block because of the encryption?

Edit: As in typical digital screetches, nail-on-blackboard stuff?

robbage wrote:Just curious Gav, do you actually hear anything at all, or does it just block because of the encryption?

what he said +1 ?????

robbage wrote: Edit: As in typical digital screetches, nail-on-blackboard stuff?

on the 396T you get a second of that before the scanner realises its encrypted and it just comes up ENC and mutes the audio.

vk6hgr wrote:

robbage wrote: Edit: As in typical digital screetches, nail-on-blackboard stuff?

on the 396T you get a second of that before the scanner realises its encrypted and it just comes up ENC and mutes the audio.

is that your scanner making it (ENC) and if so would it not just be able to be modified so it doesn't do that??

woobla1 wrote:

vk6hgr wrote:

robbage wrote: Edit: As in typical digital screetches, nail-on-blackboard stuff?

on the 396T you get a second of that before the scanner realises its encrypted and it just comes up ENC and mutes the audio.

is that your scanner making it (ENC) and if so would it not just be able to be modified so it doesn't do that??

But then it would just be digital screeches non stop? Encrypted is encrypted, you can't just turn it off at the end user.

yorky wrote: But then it would just be digital screeches non stop? Encrypted is encrypted, you can't just turn it off at the end user.

That's it.

If other agencies decide to come onboard, they may not bother with the hassle of encryption and it might be useful to track the VKI network. As for now, it's purely out of technical interest...

I am sorry about my sudden arrival back but I have just resurfaced back on the board after about three months of pretty solid shift work (staff shortages etc)
For those who don't know who I am, I am domiciled in Sydney and into anything scanning and in particular trunking in its various forms (MPT1327, LTR, Motorola Type 2, TETRA etc)
A lot of the issues you folk are facing have been replicated in each capital city to some degree or another, particularly Melbourne
I just getting myself up to speed with what happening in Perth.
I am going to do some research on what frequencies the P25 9600 baud trunking is and where the sites are, so I hope to post on that shortly.
The one thing I would ask is anybody running Unitrunker via discriminator tap on any of the P25 trunking sites or in possession of the lastest GRE.com PSR500 or 600 scanners which using the latest firmware can show the Talkgroups and RIDS of trunking systems.


Grant

PS I just found a net reference to further expansion of the Police network through Western Australia to either P25 conventional or where is close to Perth extension of the P25 trunking network. Are you folk aware of this?