DMR Question

[tvengr]

What happens when two users attempt to talk at the same time with different TGID's assigned to the same slot?

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Harrisburg School District​

Frequency	License	Type	Tone	Alpha Tag	Description	Mode	Tag
462.0125	WQYY723	RM	CC 4 TG 2011 SL 1	Harr School 2011	Operations 2011	DMR	Schools
462.0125	WQYY723	RM	CC 4 TG 2016 SL 1	Harr School 2016	Operations 2016	DMR	Schools

 

[GTR8000]

If both talkgroups are truly strapped to the same slot, they'll get a busy bonk. Seems odd that they would do something silly like that, completely defeats the purpose of having a TDMA repeater. Of course there may well be additional talkgroups that aren't documented, all sharing the same repeater, and so it would be first come, first serve with regards to the assignment of available slots.

 

[RaleighGuy]

Just because they were submitted (and monitored only on) slot 1 doesn't mean they aren't authorized to use slot 2, there just may not have been enough traffic to push them onto slot 2.

 

[tvengr]

Thank you! I agree that it defeats the purpose of TDMA. Even if there are more TGID's, there is less chance of a conflict if all TGID.s are mapped to any slot.

 

[RFI-EMI-GUY]

If both talkgroups are truly strapped to the same slot, they'll get a busy bonk. Seems odd that they would do something silly like that, completely defeats the purpose of having a TDMA repeater. Of course there may well be additional talkgroups that aren't documented, all sharing the same repeater, and so it would be first come, first serve with regards to the assignment of available slots.

If you have low priority, low traffic talk groups, they can share a slot. No different than a community repeater or simplex with different CTCSS tones. It is making best use of resources.

 

[RFI-EMI-GUY]

Thank you! I agree that it defeats the purpose of TDMA. Even if there are more TGID's, there is less chance of a conflict if all TGID.s are mapped to any slot.

You would soon run out of slots as there are only two per RF repeater channel.

 

[Ubbe]

You would soon run out of slots as there are only two per RF repeater channel.

I have seen that configuration used at several places. If a radio tech are replacing a system of several standalone analog repeaters using subtones, he sometimes just copy that system configuration into a new DMR system as if each old channel are a time slot in the DMR system.

The radios and basestations with controllers are then not costing much at all and are just a plug&play into the old antenna system and users have prior to that been given new DMR radios with analog channels programmed to work in the old system. At a certain date and time they switch over to DMR and users just use the new radios in the exact same way as they did in the old system, except now they need to count "Mississippi One" when they push their PTT button until their voice are heard on the channel.

/Ubbe

 

[IC-R20]

I have seen that configuration used at several places. If a radio tech are replacing a system of several standalone analog repeaters using subtones, he sometimes just copy that system configuration into a new DMR system as if each old channel are a time slot in the DMR system.

The radios and basestations with controllers are then not costing much at all and are just a plug&play into the old antenna system and users have prior to that been given new DMR radios with analog channels programmed to work in the old system. At a certain date and time they switch over to DMR and users just use the new radios in the exact same way as they did in the old system, except now they need to count "Mississippi One" when they push their PTT button until their voice are heard on the channel.

/Ubbe

They don't have that *Bleep!* option like P25 radios do? That way you can just tell people to talk after the beep.

 

[Ubbe]

I guess they have those ready-to-talk tones but I have one user that was part of a MPT-1327 system but now have their own conventional DMR channel and often I can hear something like "nt shoot" and the other guy asks him to repeat and it's the same "nt shoot" and then he is asked to speak more slowly and "o-n-t s-h-o-o-t" are heard. It's difficult to re-learn something they have been doing for 10-15 years. It's easier if they never have used an analog radio prior to go digital.

Memory chips are relative cheap so why doesn't digital radios have an audio delay function that instantly captures the mic audio when PTT are pushed and delayed by 300mS into the codec and transmit are held 300mS after the PTT are released. I did something like that for a repeater that used subtones, that I used a $100 delay unit for home studio work to delay the audio from the receiver so that the transmitter had time to generate a subtone and the mobiles open up their audio and then the delayed audio where transmitted.

/Ubbe

 

[IC-R20]

Nice. A local System Fusion repeater in my area does something like that with a 2 second delay between I/O