FreeDMR-512.web3 Frequently Asked Questions


Q1. Why are Talk Groups on different Time Slots on different repeaters?

A. FreeDMR has many servers to choose from (three in Australia) and each may be configured slightly differently. Each Repeater or Hotspot can connect to any of these servers world wide, which in turn can also be configured differently. Try to be aware of these differences. For example, FreeDMR allows you to configure Talk Groups as you see fit. (Where you have administrator rights. For example, your hotspot.) There is no matrix to say what TG's are allowed or to specify a time slot.

Q2. Why FreeDMR instead of BrandMeister, VK-DMR, TGIF, or another network?

A. Why not? Just like there are many brands of cars, the same is true of DMR networks. It can be a personal choice. FreeDMR uses open software and has many servers in a peer to peer arrangement which means no single entity can control the network and that ensures the network can develop with competition and offers choice.

Q3. How do I lower my Loss and BEP (Bit Error rate) on my hotspot?

A. The quick and easy way is to make calls to the parrot on TG9990 with the pi-star dashboard set to Expert Mode. Goto the Configuration menu and login, then select the Expert Mode menu, and finally, MMDVMHost. Scroll down to the MODEM stanza. Locate RXOffset and TXOffset settings. Now it is a trial and error process. Note current settings and then change the values after transmitting to the parrot and observe the Loss and BEP on transmit and receive on the dashboard. The goal is to get Loss to 0% and Bit Error Rate (BEP) below 1%. You may have to average the results as they might vary.

Q4. What is a kerchunk?

A. In common usage the definition of kerchunk is, "with a sudden heavy blow or thump". (Wiktionary) For amateur's in general the term kerchunk means to key up the repeater to see if it is there. For amateurs using the digital mode it ois user to user activate a talk group. It takes a few seconds on the Push-to-Talk (PTT) button for the user to activate most repeaters. This results in a kerchunk sound. See: "What is User Activated". The servers connect all the repeaters and hotspots that have connected to them to each other. On a hotspot you select a Server by selecting it in your configuration usually in the DMR Master dropdown box in Pi-Star. On a repeater the server is selected by the administrator. Who gets relayed to who is determined by selecting a Talk Group (TG) in one of the two Time Slots (TS) available. TG on TS can be redirected to other TG's and TS by the Rewrite rules configured into the repeater or Hotspot. To further complicate this Gateways allow for different TG to connect to other modes, For example Yaesu System Fusion, P25, D-Star, NXDN, M17, and even FM. Because audio can be encoded by different methods, Gateway connection often involve transcoding. Digital is a very interconnected mode. A more detailed guide can be found on this Ailunce Page: How to Set RX TX Offsets

Q6.What is the difference between a Static TG compared with a User Activated TG?

A. Hotspots and repeaters can be configured with selected TG's to be static. Static TG's listen to all traffic all the time and are available to transmit on all the time. You will be able to transmit straight off. User Activated on the other hand, require you, as the name suggests, to activate the Talk Group. That is, bring it online, by transmitting to the TG for a few seconds and then stopping for a second before again transmitting with your message. The process is often referred to by the term, "kerchunking". User activation provides for improved network efficiency as only the repeaters and hotspots necessary to connect the parties are utilised leaving the others idle or for use by others.

Q7. What do all those labels in the DMR Options actually do?

A. As an example I will explain this DMR Options string:

"TS1=505,530,2350;DIAL=0;VOICE=1;LANG=en_GB;SINGLE=1;TIMER=10;" Q8. Which Time Slot do I use in the Options String on a simplex Hotspot, TS1=505 or TS2=505?

A. The answer is, it does not matter because your setting is ignored. A simplex hotspot can only transmit on TS2 so any setting is overridden to TS2 as you will see on the server dashboard TS2 is used for both transmit and receive. The time slots are used between the radio and the repeater/hotspot so two conversations can carry on simultaneously, however, on a simplex hotspot you are limited to one conservation at a time.
NOTE. This is not the case on a duplex hotspot where you have to decide which TG's you want to use at the same time and therefore which TG goes on which TS.

Q9. What is User Activated?

A. Some Talk Groups will not be heard or available for transmission until User Activated. Hold the PTT for five seconds then release the PTT. Then successive use of Push-to-Talk will allow communication to occur until the timer expires which is configured on the repeater or the hotspot you are accessing. This is usually 10 to 15 min.

Q10.How do I select Talk Group 5050 on a Retevis RT3s DMR Handheld?


By using the green ”menu/confirm” button and the “up/down” arrows select.    
   Select    ZONE
   Then      ZONE LIST 
   Then      FREE DMR
   Then      ON
The “Free DMR” zone is now selected, this is further 
subdivided into twelve talk groups (below) which are 
arranged in an endless list and selected by the 
transceiver’s rotary talk group selector.  

                              Hot 505-1
                              Hot 5050-1  
                              Hot 5052-1
                              Hot 9990-1
                      RBA 505-2
                      RBA 5050-2
                      RBA 5052-2  
                      RBA 9990-2
                      RDB 505-2
                              RDB 5050-2
                              RDB 5052-2
                              RDB 9990-2 
(Credited to: Rod, VK4RA)

Glenn Lyons VK4PK
Ver:gnl20230308 - published v1.0