DMR Roaming

There are 2 DMR Roaming systems of which only one is currently functional:

  • Tier 2 IP Site Connect Mode Roam
  • Brandmeister Based Roam (not yet functional)

The idea is that as you travel from one repeater’s coverage to another, much like cellphones do, the HT or Mobile radio will automatically change to the new repeater frequency and maintains the same Talk Group and thus QSO. N1ATP repeaters are a combination of Motorola and Hytera. The system is really cool. By programming a Motorola or Hytera HT or Mobile by Talk Group and a roam list the radio switches frequencies accordingly to maintain the same talk group.

Knut uses this method as he travels between his two repeater’s coverage. With this said, the radio must have roam capability. The “$100” TYT MD380/390 level of radios do not support, only the more expensive radios.

In Connecticut, a statewide ARES system has been implemented with this capability. In theory, a user can simply turn on his Motorola or Hytera radio and select a Talk Group and the radio will automatically figure out which repeater to use.

The COMMUTER

A commuter who travels through several repeater’s coverage could have an automatic switchover between the sites. No need to run out of coverage, then switch Zone and Channel to match up to the next repeater’s frequency etc. I am sure you have heard that guy who disappears for a few and comes back to explain why he was gone.

MOBILE

CT ARES holds a net on Sunday night about the time I commonly travel from North Central Connecticut to Western Massachusetts (the Berkshires). The net is on the CT ARES UHF DMR system which covers the state pretty much from corner to corner. My travels is just north on a westerly “course” (MA-57) through very hilly terrain. It is common that my Motorola XPR4550 switches between 4-5 repeater sites on an ongoing basis and I maintain connection 95% of the time. The signal strength varies from 0 to 5 bars, but with perfect audio. It is fascinating to watch the radio picking the repeaters on the fly.

PUBLIC SERVICE EVENTS

I have used the feature during Public Service Events where I travel back and forth between the Start Area and Finish Area repeater coverage. Much simpler than manually changing channels or “flipping” to the fill-in X-Band repeater commonly used in events. Roaming is seamless to the user, much like a cellphone system.

Great Presentation on a Ham Event Utilizing ROAM

The YouTube video presents an event where balloon chasers are remaining on the same TG while automatically switching between 3 repeater-sites as they are chasing. All without touching the channel selector….. The better part is towards the end of the movie.

Watch Video on YouTube

The Video is from www.livefromthehamshack.tv

TO ROAM…..

Create a channel with the correct CC, TS and TG for each repeater you will be traveling between. Make sure IP Connect is checked. This will only work with “real” DMR Repeaters which has IP Connect like a Motorola XPR or SLR series or Hytera RD series. It will not work with hotspots and most home-brew repeaters.

Create a ROAMing list.

Add the channel in the same way as a scan list, however as a TG specific roam list. Name the roam list the TG, E.G.: TG3100.

Build Sequence from left to finally use >>>>>>>>>>
  Channel List Details   Roam List TG3100 Roam List TG310 Roam List TG311 Roam List TGxxx   Zone Roam
Ch 1 Rptr 1 Freq CC TS IP Site Connect TG3100   Ch 1 Ch 21 Ch 31 Ch x1   Roam TG3100
Ch 2 Rptr 2 Freq CC TS IP Site Connect TG3100   Ch 2 Ch 22 Ch 32 Ch x2   Roam TG310
etc etc   etc etc etc etc   Roam TG311
Ch 21 Rptr 1 Freq CC TS IP Site Connect TG310             Roam TGxxx
Ch 22 Rptr 2 Freq CC TS TG310   RSSI should be round -108. Experimentation may be needed.     These are the channels you actually use
etc etc            
Ch 31 Rptr 1 Freq CC TS IP Site Connect TG311            
Ch 32 Rptr 2 Freq CC TS IP Site Connect TG311            
etc etc            
Ch x1 Rptr 1 Freq CC TS IP Site Connect TGxxx              
Ch x2 Rptr 2 Freq CC TS IP Site Connect TGxxx              
etc etc              

As you move and loose one repeater, the radio will switch to the next repeater in the roam list with adequate signal (usually better than -108db) while your main on the same talk group. Your radio will actually ping the repeater and log on (register).

The difference between scan and roam is that Scan keeps scanning until a signal is received, while a roam radio checks in with the repeater in the roam list and remains locked on that channel until the signal is too weak.

I have personally maintained the same QSO while traveling from southwest Connecticut up north through the state never really knowing which repeater I was on. This is not totally true since the radio display will tell you based on your naming convention of each channels. Point is, it is very much like a cellphone. It just works when the repeaters have some overlapping coverage! It also conveniently works as you travel from one coverage to another. Again, the difference is from scan is that the radio registers with a usable repeater on a TG as you specify.

MOBILE HOTSPOT

A Mobile Hotspot can kind of accomplish the same thing provided cell data coverage is seamless. Through Brandmeister both worlds can be combined for max flexibility. They both have independent advantages.

REPEATER OWNER

Since I don’t have access to prime repeater locations (mountain peaks or tall towers), I can place the repeaters at a more moderate elevation and re-use the frequency pairs in cells like a cellphone system. Takes more hardware which may still be easier than getting access to the prime locations. This also simplifies temporary event repeater kits which may connected together with cell data modems for ad-hoc use.

I Love The Roaming Feature!

I don’t like home-brew repeaters which do not employ standard DMR Tier 2 options!

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