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AL0Y > TECH 08.12.20 23:16l 25 Lines 3506 Bytes #999 (0) @ WW
BID : 10746_AL0Y
Read: GUEST
Subj: DMR Concepts
Path: IW8PGT<IZ3LSV<IK5FKA<IK5FKA<PE1RRR<W0ARP<AL0Y
Sent: 201208/2115Z 10746@AL0Y.#NNJ.NJ.USA.NOAM BPQ6.0.20
DMR Concepts
===============
Just as FM and D-STAR require more than just entering a frequency, DMR has its own unique set of parameters to program. Don't panic, they do make sense, especially if you remember DMR is designed for the commercial market, and we have adapted it for Amateur use.
To put things simply, there are several "Big Ideas" with DMR: Radio ID, Color Code, Timeslot, Talkgroup and Zones:
Radio ID (Subscriber ID):
DMR is digital, and networked, so each radio has a unique ID number to identify it on the network. In the D-STAR world this corresponds to the "MYCALL" parameter. To obtain a radio ID, go to: https://www.radioid.net/register#!
Color Code:
This is the DMR version of PL.
Timeslot:
DMR uses magic known as "Time Division Multiple Access" (TDMA). In Simple Ham English, this means the repeater can support two simultaneous conversations by alternating between two timeslots. About 30ms is given to timeslot 1, then the transmitter flips to timeslot 2 for 30ms, then back to timeslot 1, and then to timeslot 2; you get the idea. Something like the mom who speaks to her 2 kids, allotting each of them 30ms to talk. Since you transmit on just one timeslot, your radio's battery last longer as it is really only transmitting about half the time you have the PTT keyed. In other words, the repeater's Time is Divided such that Multiple hams can have Access (TDMA).
Talkgroups:
DMR is designed for the commercial market where radio users typically have something in common, such as Security, Engineering, Parade Operations, etc. It isn't very efficient to have separate repeater pairs for each group, so DMR uses "Talkgroups" to group together users who want to talk to each other. On our DMR repeaters we have several Talkgroups that allow you to talk to geographically increasing areas: local, regional, statewide, all the way up to worldwide. Talkgroups are also either "Always On" (Static for BrandMeister) or "User Activated" (Dynamic for BrandMeister). "Static" or "Always On" means just that, network traffic to this talkgroup is always on. "Dynamic" or "User Activated" talkgroups have a timer associated with them, typically 10 minutes. The practical side of this is that after 10 minutes of local inactivity on a User Activated talkgroup, it is dropped from the network connection. To start listening to a User Activated talkgroup, key up, and you probably want to talk at least once every 10 minutes as well in order to keep the network feed.
Zones:
Think of a "Zone" as a way to organize a group of channels. For most folks there are several talkgroups they wish to use, and several repeaters as well. Multiply that number of talkgroups by the number of DMR repeaters you want to use and this can make for a lot of channels. How can we keep things organized? We use Zones to give us a convenient way to organize these talkgroups. Again, remember that DMR is a commercial thing. We group our channels into Zones for ease of use, such as putting all the Parade Ops talkgroups into one Zone. It is easier to select a channel within a Zone than it is to scroll through hundreds of channels to find the right combination of repeater and talkgroup. You can set up your Zones pretty much however you like, be it a Zone for each repeater or a "Road Zone" containing the talkgroups on the different repeaters you use on your road trip. Zones can contain DMR and analog repeaters as well. Set them up so they work for you.
Original: http://www.papasys.com/dmr/DMR101/
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