Does DMR simplex use 1 time slot or 2?

[n1das]

I have experimented with the DMR simplex modes in my Hytera portables. These are the 3 modes we are talking about here and getting them mixed up.

DMR simplex modes:
1. Plain old DMR simplex mode. I don't know the exact name for it.
2.. TMDA direct mode.
3. Single frequency repeater (SFR) mode.

In what I called plain old DMR simplex mode, a subscriber transmits on a time slot tagged as either slot 1 or slot 2. There is no synchronization available to receiving radios due to no repeater being used. If you listen with an analog receiver, you will hear the chattering of a single slot transmitting. Simplex radio to radio will work but no TDMA operation is possible if you try talk with another pair of radios tagged to the other timeslot. Receiving radios will respond to either timeslot tagging. I think this is what NE1B refers to as simplex always being dual slot operation.

Hytera has TDMA direct mode where the radios interpret the timselot tagging received from another radio and respond accordingly. I have verified this by testing with 4 Hytera PD982 portables on simplex on the same frequency in TDMA direct mode. Radios in pair A will talk simplex to each other on slot 1 while the radios in pair B on slot 2 remain silent, and vice versa. Talking with a radio in pair A while simultaneously talking with a radio in pair B works like normal 2-slot operation does on a repeater. I've had 2 separate simplex conversations simultaneously on the same frequency, using 4 PD982i subscribers. The radios dynamically serve as a timing master for the other receiving radios for 2-slot TDMA operation. In TDMA direct mode, this is where it does matter which timeslot you select for simplex use. When listening on an analog receiver, when a single slot is being used, you will hear the chattering of a single slot. When both slots are in use like when I simultaneously transmit with a radio on in pair A on slot 1 and a radio in pair B on slot 2, you will hear the normal TDMA buzz which sounds like a repeater transmitting.

Single frequency repeater (SFR) mode works as speedway_navigator described and demonstrated in the video. I don't have SFR in my PD982i UHF portables. That's my next upgrade.

 

[speedway_navigator]

I've had 2 separate simplex conversations simultaneously on the same frequency, using 4 PD982i subscribers.

When I was testing this last night I kept talking across both slots, then I removed my cranium from my rectal cavity and realized I had the same TG in each personality. I also forgot to select the designated TX slot for pseudo trunking during a test which also didn't work.

 

[n1das]

When I was testing this last night I kept talking across both slots, then I removed my cranium from my rectal cavity and realized I had the same TG in each personality. I also forgot to select the designated TX slot for pseudo trunking during a test which also didn't work.

During my 4 radio testing, all radios had the same TG (99) in each personality. The difference between personalities was the timeslot selected. I had to specifically select the timeslot to be used and had TDMA Direct Mode enabled. I found TDMA Direct Mode did not work with pseudo trunking selected.

I just checked my Hytera PD982 programming to refresh my memory. I found Hytera took the TDMA Direct Mode away with the latest firmware updates which made the radio into a PD982i. I suspect the change was due to features which had to go away because of the settlement of the Motorola/Hytera lawsuit.

 

[speedway_navigator]

I suspect the change was due to features which had to go away because of the settlement of the Motorola/Hytera lawsuit.

Yes, that went away with v9, the eye series...
Pseudo trunk does the same thing but it's not in the BD series. Haven't heard anymore about the suit recently, I'm sure the PR battle will start before the next round of litigation does.