DMR vs. Analog (a primer)

The point of this article is to quickly explain the difference between analog amateur radio and digital voice amateur radio, in simple terms. This is not an exhaustive description and I will not delve into the theory of the two modes.

Teaser: An analog repeater supports 1 channel of communication and a DMR (digital) repeater supports 2 channels of communication.


Most hams are familiar with analog 2-Meter HT and mobile operation. To operate an analog radio on a local 2-Meter repeater, one must know the (1) frequency of the repeater, (2) the transmit offset of the repeater, and (3) the PL tone (code) being used to access the repeater. This is relatively familiar and fairly simple to show. For instance:

  • Frequency= 146.910 MHz
  • Offset= (- 0.600 KHz)
  • PL tone= 100.0 Hz

That’s it! You are on the air and talking to other hams on the “91” repeater. The “91” repeater can handle one channel of communication at-a-time and everybody hears the conversation as long as they are also tuned to 146.910 MHz. DONE! Analog– the sound of your voice coming out of your mouth is analog, varying in frequency tones, in smooth transitions.


DMR (Digital Mobile Radio) is a bit more complicated and may result in a minor stroke for some hams if the concept isn’t grasped. The extra complication could result in many hams not exploring DMR as a result, and resorting to going out to mow their lawn, instead. Let’s see if I can attempt to simplify this for you, at least as an introduction, so that when you go out to mow your lawn, you can digest what you just read while pushing the mower.

A digital signal sounds much different to the human ear than analog sound. A digital signal sounds like computer data (much like the old dial-up computers sounded like many years ago)— just digital, screaming hash that could be used to torture somebody into revealing the combination to their safe. A digital radio converts sweet, smooth-sounding human voice into screeching computer hash, which must be decoded on the other end and converted back into human voice, again. If one were to listen to a digital signal on a normal radio scanner, all that would be heard is the ear-piercing screeching sound similar to that of a yeti, while having its claws pulled out one-by-one. I digress; back on point.

If the “91” repeater were to be converted from an analog repeater to a DMR (digital) repeater, then additional parameters are required to talk on the repeater. As before, the (1) frequency of the repeater is required, (2) the transmit offset frequency, and (3) the Color Code of the repeater– in analog world, we use PL-tones, in DMR world we use Color Codes (abbreviated CC)- so the CC is similar to a PL-tone. So far, the two systems are the same.

In addition to the above, the DMR operator must also know the (4) Time Slot (abbreviated TS) being used, and (5) the Talk Group (abbreviated TG) being used. STROKE OUT– this is where you give up and go mow your lawn!

  • Frequency= 146.910 MHz
  • Offset= (-0.600 KHz)
  • Color Code= CC1
  • Time Slot= TS1 and/or TS2
  • Talk Group= whatever is assigned to the repeater by the repeater builder.

Time Slots

What the heck is a Time Slot? Please recall earlier in this article I mentioned that an analog repeater supports only 1 communication channel, but a DMR repeater supports 2 communication channels? Well, a DMR repeater has two Time Slots– or two channels of communication– available to its users, TS1 and TS2. Now, that wasn’t so bad, right? Two separate, individual, independent, simultaneous, unrelated, un-interfering conversations can take place on a DMR repeater, “Believe It Or Not”. For instance, TS1 could be used to provide event communication for the UP200 Sled Dog Race held on the weekend of February 14 in Marquette. Michigan, while TS2 is being used by Bob talking to his wife, Mary on their way home from work (Bob and Mary are licensed hams, incidentally). The twain shalt not meet; Bob and Mary are unaware of the Sled Dog Race and visa versa. Wow, it’s like getting two repeaters for the price of one. SOLD!

Talk Group

What the heck is a Talk Group? How many of you are familiar with Echolink or IRLP or Allstar, all Voice-Over-Internet (VOiP) systems? Everybody that signs up for Echolink receives an Echolink number, a unique number assigned to only one ham and no two numbers are the same– just like every cellphone has a unique phone number. Also in Echolink, there are rooms called Conference Rooms (also assigned a unique number), which is a general place for many hams to collect as a group to perform a net or a rag chew session. Well, DMR has similar requirements and these are called Talk Groups– a group of hams gathering together– get it?

Just like Echolink, every DMR ham subscriber is assigned a unique ID number; every DMR repeater is assigned a unique ID number, and there are hundreds of rooms (Talk Groups) available, all assigned a unique ID number. For instance, my ID is 3138407 and my repeater is 311795. A popular TG in Michigan is 3126, which is the Michigan Statewide Talk Group (TG 3126)– every state has their own statewide group.

In conclusion- an example:

Sticking with the “91” repeater example, above, I am the repeater builder and I decided to set the Time Slots the way I wanted to, based on popular demand of the local DMR hams.

  • TS1= 3126 (the Michigan Statewide TG)
  • TS2= Local 9 (TG 9), Tac310 (TG 310), North America (TG 3169)

Oh, by the way, yes I can assign more than 1 Talk Group per Time Slot, but only 1 of those TGs can be active (turned on) at a time.

So, to program your new DMR radio (by the way, the program in the DMR radio is called a Code Plug) to use the above Time Slots on the “91” repeater, each Talk Group would be programmed in as a separate channel in the radio. For instance:

Channel 1 (Mich State)
146.910 MHz, offset -0.600 KHz
TG 3126

Channel 2 (Local Chat)
146.910 MHz, offset -0.600 KHz
TG 9

Channel 3 (Tac 310)
146.910 MHz, offset -0.600 KHz
TG 310

Take notice that each channel (on the radio) in this example is programmed with the same basic repeater information- frequency, offset, and Color Code- but the Time Slot and Talk Group are different. So, unlike analog radio memory channels, a DMR channel determines the Talk Group being selected on the same repeater <head explosion>. Cool, right?

So there you have it. I hope this gets you started as an introduction to DMR. Once you begin thinking in these terms, exploring DMR further will be easier and programming your new DMR radio (creating a new code plug) will make more sense.

73 de KB0p