Slots and talk groups
One of the great advantages of DMR is its ability to support
two simultaneous conversations on one repeater using Time Division Multiple
Access (TDMA). The two slot TDMA system
is unique in amateur digital modes.
Our DMR network has many talk groups spread across the two
slots. Some of these are static – i.e.
always on, and some are User Activated (UA) – they need to be keyed
(“kerchunked”) up, and time out after a period of inactivity (normally 15
You can see the static groups on the IPSC server web page: http://rpt.vkdmr.com/ipsc/
The static groups are shown in the 5th and 8th
columns alongside each repeater.
There are a lot of talk groups, and they can be confusing. They are described at https://vkdmr.com/using-dmr/
Although the network is quiet during the day, the user base
has increased significantly (and continues to do so), so there will be
occasions where there are two, sometimes three groups of users trying to use
both time slots.
When user numbers were low, it didn’t really matter if you
used a static talk group, but these days, a static group can hold up a time
slot and make the network difficult to use for others.
This is particularly the case with the State based 380x
series talk groups on time slot 2. If
two stations are talking on, say, 3802, it locks the slot onto 3802 for all VK2
repeaters – other VK2 users are unable to use the main calling talk group –
Whether you are accessing the network via a repeater or a hotspot, you should use talk groups that key up the minimum number of repeaters if you wish to chat with another station after QSY’ing off 505 – this will ensure that the maximum number of users can access the network.
If you are working a station on the same repeater, use TG9 on
time slot 1 – this only keys the one repeater on one time slot.
If you are using two separate repeaters, switch to a UA talk
group. Most UA talk groups are on time
slot 1, but there is one available on slot 2: TG3800.
As with all UA talk groups, TG3800 only connects the
repeaters used in the contact – this keeps the other repeaters free on time
slot 2 for stations to call on the main VK calling “channel”: TG505.
UA “chat” talk groups are listed below:
*3810 is intended for WICEN but is available for general use
outside WICEN activities.
If possible, it is always handy to have the IPSC server web
page running on a PC/tablet/phone – this gives you an overview of network
TG5 on time slot 1 is a special case – it is intended for national broadcasts and nets, so is intentionally static. It should not be used for other traffic.