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The "iCall" Talkgroup

The iCall Talkgroup Project has been shelved on DCI due to lack of interest - this is now legacy page.

The "iCall" (Travelers) talkgroup was the first conceived in September of 2015 in an effort to address the problems of traveling DMR hams to be able to (seamlessly) make contact back home to their local repeater(s).  The current international talkgroups are generally language specific and/or on PTT.  This does not provide the ability to be able to "phone home" or an effective hailing talkgroup for travelers, tourists or hams in general wherever they are located in the world.  With the availability of a true hailing talkgroup, even those in the same country can use the TG to make contact back to their home repeater and then the participants can switch to TAC 310, 311, 312, etc. in the USA, TAC 1 or other PTT talkgroups that they may have in common around the world.  Obviously, the key is the hailing talkgroup first, then the alternative PTT talkgroup to switch to for the conversation.

At this time, the closest international option already in place, is TAC 1, which is PTT on most or all c-Bridges.  What is lacking is the full time hailing channel.  iCall would address that key issue.  Once contact has been made on iCall, hams should switch to TAC 1 or other appropriate talkgroup to continue their conversation with no additional impact to all the iCall repeaters which have adopted this service for the benefit of all DMR hams.  For this talkgroup to work effectively for everyone and to minimize the disruption to the repeaters supporting iCall, this should be used as a hailing talkgroup ONLY, then conversations can move to TAC 1.  This policy is already in effect on many wide area talkgroups as TAC 310 has shown.  In effect, iCall and TAC 1 will operate as a talkgroup pair, so both will be needed on participating networks and their repeater managers.

Included below is that that Email proposal.  At this time, the concept has met with little support among the independent c-Bridge operators (ICBO's).  But then TAC 310 was greeted with active hostility before and after it's introduction but ultimately has become one the the most useful talkgroups (now with 311 and 312).

Changes have been made to address the concerns raised by the original proposal.  Those changes hopefully will bring forward more c-Bridges to adopt the proposal.  If it does not work for your c-Bridge or your managers, then go PTT or dump it.  But why not give the proposal a chance to work?  Remember TAC 310 had a huge hurtle being adopted but it succeeded over the course of several years.  This idea is not designed to benefit the adopters generally but more the wider DMR community.  Maybe that is the problem; few want to (proactively) better the environment for the larger DMR group, unless there is something in it for them, directly and immediately.  I choose not to have that myopic view and am willing to foster something that holds promise to many over the few.

The initial and primary concerns appear to center around adopting this TG as a full time talkgroup with less to no opposition voiced against the concept if the talkgroup is carried as PTT.  But PTT undermines the usefulness and TAC 1 is already adopted for PTT International, any language.  So more work on the FT/PTT aspect will need to be pursued to assuage the community concerns.  The concern seems to be primarily that of a negative traffic impact locally and dismissing or ignoring the positive benefits  more generally.  The concerns can be addressed and mitigated, hopefully to the point that c-Bridge admins (and their repeater owners) would be willing to try it and provide input on any further needed mitigation.


  • TG is for hailing only, conversations are to move to TAC 1 immediately (or other talkgroup in common between the parties).  International use would be common but some hailing within the USA is possible if no other talkgroups are available

  • The iCall Talkgroup ID is: 8952  (TAC 1 is 8951)

  • The CC is 93 available from: icbo-2 and the secondary server is pending until service is provided  by a TG server  (minimum of 5 c-Bridges must carry iCall before it can move to a talkgroup server)

  • Suggested iCall settings are full time for all repeaters, either TS is fine

    • Ideally, iCall and TAC 1 (TAC 310, TAC 311, TAC 312, etc) should be on the same timeslot

      •  This would assure that TAC 1 is available if iCall hailing was successful, but optional

    • Use a very short hold-off timer of 1 minute for iCall to further limit potential misuse or longer conversations on the hailing talkgroup

      • Creative use of priority and "and" logic in Super Groups will further lessen misuse

    • All repeater may use an overnight mode for PTT local time if that will address concerns

    • Short talk timers may be used for easy break-in/turn off by local users not in the conversation

      • Remember:  use the non-default 1000 millisecond "Group Call Hang Timer" in your repeaters

    • Other mitigation options as desired to increase acceptance/adoption of TG

    • Remind users to move to TAC 1 (or other PTT TG) if they seem to be unaware of this need to switch

    ...more to follow as it develops

ORIGINAL EMAIL PROPOSAL, September 27, 2015  (Little interest initially)

I would like to have the DMR community adopt an international travelers talkgroup, especially since TAC 310 got the MARC axe last April.  So here is a rough proposal that I'd like to you to consider with and for, further discussion.

I will approach the initial proposal from the standpoint of "re-purposing" the TAC 1 TG already on the TG server and used relatively little.  TAC 1 (8951) was created to replace the loss of TAC 310 but never caught on like TAC 310 has done.  Certainly a new TG could be created and there would be some value to start from scratch for the user education value of a start-up talkgroup.


TRAVELERS TG: This TG would be carried fulltime on all c-Bridges and their managers and would be used by travelers to "phone home" while out of their home country.  It would not be used intra-state by US hams or when their was another TG path commonly available.  Enforcement of this use should not be of much issue if TAC 1 were to be renamed Travelers (or some similar distinctive label; ET, Phone Home, yada yada).  The folks in Europe (except MARC) are behind this approach generally and have adopted independant intra-country TG's and have been since TAC 310 was created.  The Travelers talkgroup would be created for the entire world of DMR users.


  • TAC 1 to be renamed Travelers (or similar)

  • Travelers to be carried full time by all managers

  • Hold-off timers set slightly longer, possibly 10 minutes

  • Limit conversations to 10 minutes to minimize impact on local use of repeaters

  • Allow 3 or 5 seconds for talk cycles to allow uninterested users to PTT off the Travelers TG

    • Repeaters should have their Group Call Hang timer set to 1 second in this PTT world for easier access to the time slot

    • If a repeater has the stock 3 second hang time, then a 5 second delay in talk cycles would need to be requested

  • Any language may be used


  • Easy use and always on makes this truly an international talkgroup

  • Doesn't require the Slot3/4 approach for handling visitors

  • Destination cities (repeaters) can choose to carry Travelers via PTT if they feel that is a must or to aid in its adoption

    • Hawaii, Vancouver BC, Italy, Seattle, New York, Switzerland etc. could take that approach

    • Littlerock, Mazama, Walnut Creek, Bodega Bay would be full time as they are not considered destinations (PTT would not be very beneficial)

  • 10 minute conversations are reasonable middle ground for a Phone Home conversation and minimal impact to the local repeaters.

  • Can PTT off timer for the Travelers TG if it does bother the local repeaters not participating in the conversation (10-15 minutes suggested if needed)

  • Good will and a better more friendly approach to DMR Ham radio than currently exhibited by many "groups"

  • DCI would host a web page for educating users on the use of the Travelers TG to aid in the proper use and success of the Travelers TG


  • Another TG to carry and program for (less of an issue if TAC 1 is repurposed)

  • Full time can pose issues if misused

    • Enforcement/education a must and gentle reminders over the air suggested (always the potential to upset folks, so a gentle hand helpful)

    • Longer hold-off timers for managers with priority TG's, IE: turn-off Travelers when active if not interested in the conversation

  • Foreign language may be a bother to local users, again PTT it off via timers if desired to mitigate

  • Users need an opening so that repeaters can PTT out to clear the timeslot (this is always problematic, waiting a few seconds)

DISCUSSION:  Fire away...


Robert (N5QM),  as I don't have the list of Emails of c-Bridge admins that currently carry TAC 1 (or the others who may have some interest), would you be willing to at some point send out this or distillation of the proposal for wider consideration if this proposal gets that far down the road?

While I bowed out of the national DMR scene after tiring of the endless and essentially fruitless efforts, some might question why (including myself) I am proposing another idea that will prod the MARC machine, but I see the idea of an international TG that will work for all hams all over the world.  That I think, is one of the things missing from DMR and thought so back when I created TAC 310.  The big difference though is the need for it to be on full time.  I think it is worth a try.  Worst case, if it fails, it can simply evolve to go back to PTT TG as repeater owners/c-Bridge admins choose.  Even that would not be a complete failure and would still provide PTT by schedule or SMS alerts, etc. for the traveling hams.

My thanks in advance for any consideration.

-- Mike, NO7RF, Mazama Washington, no7rf@trbo.orgwww.trbo.org


Revised: 05/21/2017 09:00