This class is focused on the DMR system specific to Maine, which is a C-Bridge / DMR-MARC system, but the content can be applied to almost any MotoTRBO system. A few DMR radios work fine through repeaters, but cope badly with radio to radio operation because with a repeater they can hear it's timing and follow it - but radio to radio means the timing is more difficult. By the end of the class it is my hope that you will understand how the DMR repeater system works and also understand the terms to be able program your radio to access the system.
The alternative is Frequency Domain systems - these use two narrower channels in the space of one ordinary one to achieve similar things.The really tricky thing is that radios have to synchronise the transmit receive switching, or everything falls apart. These are called Time Domain systems - multiple users can use them at the same time. It sounds a bit odd, but DMR has a lot of possibilities - a repeater with the usual different input and output frequencies is very clever. They switch in and out of transmit very rapidly so it's possible to have a 'kind' of repeater setup receiving on slot 2 and transmitting on slot one.
If you look up DMR in wiki - you'll see the comments on Slot 1 and Slot 2 - these are the two channels Bill mentions above. Bridgecomm has great marketing and they definitely over-hype DMR. Lately I've heard a lot of newbies with UV878 radios from Bridgcomm and I can almost hear the disappointment in their voices from what (or lack of what) they hear on the air. My hope was that Hams would take advantage of the digital mode to improve local and statewide communications especially for emergency preparedness but so far that does not appear to be happening. I've enjoyed the challenge of setting up and configuring the equipment. I thought that maybe if I used a hotspot I would hear more on some of the other networks but it's very sporadic. I was disappointed in the lack of local activity and then even more disappointed in the lack of activity when linked to some of the Brandmeister regional and national talk groups. I first bought an inexpensive hand-held (MD-380) and programmed it for a couple of local repeaters.
I'll agree that using DMR over a repeater or hotspot is about as challenging as using Skype to communicate. One of the biggest challenges for me back then was getting and converting commercial equipment for ham use to keep the expense down. I've been a ham since the late 70's and I have seen this debate about communicating before only back then it was first about using 2M FM, then about using 2M repeaters, and then later it was 440 repeaters. What this means is that two completely separate radio transmissions can be going through the repeater at the same time each radio takes turns in transmitting in short 27.5 millisecond bursts. With Tier 2 DMR, repeaters are used in a TDMA arrangement, with two 'timeslots. Just saw this so I thought I would throw in my two cents. Tier 2: Things start to get a bit more complicated here.