Question about TalkGroups

[G6FIR]

Hi everyone, I'm a return-to-the-hobby after decades out, got the kids off to Uni now so am playing again.
I came back to the QRP CW rig and antenna construction, but got a cheapo Baofeng FM handheld to see what the community was talking about. Actually quite shocking, when I used to operate over PI back in the day we had to ask for a break to get a call over the repeater and calling channel 145.500 was constantly busy. Now I listen to a "CQ" over a 70cms repeater, about every 30 minutes, rarely getting answered.

So, I thought maybe there might be a bit more action on DMR with its wider cast net. To be honest, I was quite shocked at all the development and confusing number of digital modes that used the net as a medium. I was also shocked at SDR and the WebSDR stuff like Hack Green. Absolutely amazing, it's like I've returned from a another planet to find this one had changed beyond recognition. It's all good though, I absolutely thrive on learning. I've gone the cheap route for now whilst I'm in the discovery phase. Baofeng DMR handheld, special offer from Emporium. Then ChinaSpot MMDVM clone thing, with a little OLED on it mounted to a PI GPIO with Pi-Star. Until I get a new 2m/70cm roof antenna up I am out of range of digital repeaters. A couple of evenings fiddling with these virtually undocumented gadgets and I hit my first QSO on DMR mode. Very low error rate and I didn't even need to set any offsets. Possibly the MMDVM clone and the Baofeng are equally off

Anyway, that's enough back-story waffle. I am left with some questions.

The first is talkgroups. I have configured Pi-Star with Phoenix F DMR Master and these options:

"StartRef=4400;RelinkTime=60;UserLink=1;TS1_1=9;"

However, Pi-Star is configured for TimeSlot 2, the MMDVM thing is simplex. This option string I found using search engines, seems to imply TimeSlot 1 (TS1_1=9).
Is this correct? I know I'm not supposed to be using TS1 and my list of activities on the dashboard suggests that I'm not.

The StartRef=4400 reflector option is for TG235. This is slot 1 according to Phoenix website? I don't know if this slot the same as timeslot. I am using a codeplug digital channel on the handheld set up for TG9, yet I am hearing the call outs for TG235, and these are showing as Target 9 on Pi-Star activity. And TG9 is shown as slot 2. On Phoenix website, there doesn't seem to be a reflector number for TG9.

Can anybody clarify what I should be using?

Thanks everybody, for getting through my waffling post!

[AF6VN]

The StartRef=4400 reflector option is for TG235. This is slot 1 according to Phoenix website? I don't know if this slot the same as timeslot. I am using a codeplug digital channel on the handheld set up for TG9, yet I am hearing the call outs for TG235, and these are showing as Target 9 on Pi-Star activity. And TG9 is shown as slot 2. On Phoenix website, there doesn't seem to be a reflector number for TG9.

{One reason I'm somewhat glad that US Brandmeister masters have totally disabled usage of reflectors -- since every reflector was mapped to a unique talk group anyway}

In most cases, the time slot used by the hot spot is independent of the time slot used by a repeater. Just as the color code is independent. Once the data reaches the network, about the only information that transfers is the talk group, and maybe the reflector (though that may just be something in the master, filtering what traffic it sends back to your hot spot, since the hot spot is a discrete IP/port pair -- the master just needs to track linked reflectors by that IP/Port combo). Pretty much all hotspots are ONLY time slot 2 -- so any channels you defined in the radio for use with the hot spot should be configured as TS2.

European DMR repeaters tend to be configured to use just two channels (per time slot?). One channel is used to send the reflector link request, and the other is TG 9 for use after linking. Time slots often appear to be dedicated to, say, local-only (TS1) and linked (TS2) usage. In contrast, US Brandmeister users will have a channel configured for every talk group of interest per repeater and time slot, and the time slot allowed for a talk group is controlled by the repeater operator. That said -- it does appear that the Phoenix group does have specific talk groups, rather than the "private call to link reflector, group call TG 9 to converse".

Browsing the various links, I see only time slot 2 specified for hot spot access. http://www.opendmr.net/index.php/dongle-access/ (http://www.opendmr.net/index.php/reflectors/ implies that Phoenix TG 235 is currently not linked to DMR+ reflector 4400)

Best information I've found so far is https://dmrguideuk.wordpress.com/dmr-ne ... /dmr-plus/
From that -- ignore all the Phoenix talk group numbers. You will only be using talk group 9 on time slot 2 with the hot spot. You make a private call to the DMR+ reflector number (while TG9 is the selected channel?), and use TG9 group to converse. Though a less than clear page https://dmrguideuk.wordpress.com/phoeni ... s-dongles/ (the linked https://github.com/g4klx/MMDVMHost/blob ... options.md indicates that the "static" talk groups are time slot 1 [and that start reflector is TS2], but that hot spot page implies that the traffic still comes over time slot 2 -- making for a rather mess to configure, in my mind). And there is this blurb

22nd August 2018

From the Admin Team via Paul Fuller:

Users can now connect to our Phoenix-E server to get dongle access via MMDVMs. Please set your DMR ID as your personal 7 digit number. You can use up to 9 digits, this is to allow a 2 digit suffix if you have multiple MMDVM devices. Both Dual Hats and single ones are both supported. Duals can access both TS 1 and 2, and access all phoenix talkgroups. Singles will be able to access TS2 talkgroups and reflectors via TG9. Please let me know if you have any questions.

... which just seems to confuse matters even more -- It sounds like the PhoenixF master will only accept TGs on the defined time slot, so using the TG9 and reflectors may be the best solution.

[G8SEZ]

Anyway, that's enough back-story waffle. I am left with some questions.

The first is talkgroups. I have configured Pi-Star with Phoenix F DMR Master and these options:

"StartRef=4400;RelinkTime=60;UserLink=1;TS1_1=9;"

However, Pi-Star is configured for TimeSlot 2, the MMDVM thing is simplex. This option string I found using search engines, seems to imply TimeSlot 1 (TS1_1=9).
Is this correct? I know I'm not supposed to be using TS1 and my list of activities on the dashboard suggests that I'm not.

The StartRef=4400 reflector option is for TG235. This is slot 1 according to Phoenix website? I don't know if this slot the same as timeslot. I am using a codeplug digital channel on the handheld set up for TG9, yet I am hearing the call outs for TG235, and these are showing as Target 9 on Pi-Star activity. And TG9 is shown as slot 2. On Phoenix website, there doesn't seem to be a reflector number for TG9.

Can anybody clarify what I should be using?

Thanks everybody, for getting through my waffling post!

If you are using a simplex hotspot then the timeslot is irrelevant, the radio doesn't care about it and the hotspot will sync with whatever you're transmitting.

TG9 is the talkgroup many repeaters, including those on Phoenix, use for local chats where there is no IP backhaul and the data is sent back out on the repeater RF output. For Phoenix this is on timeslot 2. If you are using TG235 via RF then it will be on slot 1.

The 4400 reflector is connecting TG235 back to your hotspot but the RF from the hotspot is sent out using TG9 (it's a convention as it's a 'local' transmission). Hence you need TG9 to be in your Rx grouplist unless you are transmitting on TG9 (which you probably are) so the audio path will be opened anyway.

There are two ways to use a hotspot, you can either set the destination using a private call to the reflector ID and then transmit to it using a TG9 group call or you can transmit to the TG you want with a group call to the TG number you want, then you will get a response on TG9 which is why you need the TG9 addition to your Rx grouplist.

If you want more info then I think this document should help:

https://dmrguideuk.wordpress.com/terminology/

but note that these things don't stay still for long. It's all very confusing it says here in small print.

HTH etc.

[G6FIR]

Thanks for the replies, you have moved me on a bit and confirmed I had the radio set up right.

I've one more question: if I want to listen to TG1 Worldwide calling group - or any talk group then I believe that I just need to program one digital channel with the contact for that group and include it in the GroupList. Is the correct ?

[AF6VN]

I can't speak for the DMR+ and/or Phoenix F masters, but... Brandmeister masters support (via their "self help" management page) defining static talk groups -- these are talk groups whose traffic will always be sent to the hot spot (and as a result, should probably be limited to talk groups with low traffic but high interest). All other talk groups fall into the "dynamic" category -- dynamic talk groups time out after something like 10-15 minutes, unless kept active by the you sending traffic to the master via the hot spot. BM /does/ keep the most-recent dynamic talk group as a "pseudo-static"; it will not time out on a hot spot (connections deemed to be "repeater" don't get pseudo-static and always time out when no one is transmitting to it).

My normal talk group is BM 3100 (US Nationwide). It appears as a pseudo-static.

I mention this as, in my case, I have the BM links to the Mi-5 Statewide-1 and Statewide-2 defined as static. My Receive Group List has all the talk groups I have an interest in. This means I can be dialed up on a channel for 3100, but still hear traffic on the two static groups. Also, should I dial up a channel for a different talk group and PTT, it then becomes the pseudo-static, and 3100 reverts to regular dynamic -- I will still hear traffic on 3100 until the master times it out.

I didn't see anything in the Phoenix web pages describing behavior when changing talk groups. It may be that you will only receive traffic on the talk group (or TG9 and reflector) that you last activated. If that is true, a receive group list may not be of significant use -- you have to dial up a channel/TG (or activate a reflector on TG9) and PTT, and the master only sends traffic on that selection back to you, you will never hear traffic for other talk groups. On that assumption, you would have to have a channel configured for TG1 (to use your example), dial it up on the radio, AND hit PTT to activate the talk group on the master<>hot spot connection. That would then be the only TG you would hear traffic from (again, this is my understanding of how the master behaves).

DMR+/Phoenix does seem to support specifying up to five static talk groups in the configuration option line... BUT it seems those are considered TS1 entries and may not be heard on a TS2 hot spot... I just don't know. After all this investigation, Brandmeister without reflectors seems much simpler to use (once one learns how to program the radio for each "channel" and set up a receive group list so that active BM talkgroups [static or dynamic] pass).

[G6FIR]

Thanks Dennis,
I think my next step will be to give BM a try.

Last night I heard a QSO on the calling channel and they moved off to TG81 (4402) for a chat. This is is very reminiscent of many years ago when people would call on 145.500 and drop down to another 25khz channel for their conversation. So I followed them, using direct dial and punching in 4402 and sure enough there they were. However, having discovered this works I decided to go back to listening on the call TG but there was nothing I could do to stop their conversation dominating my radio and Pi-Star activity. I could not get rid of them by moving channel or dialing in a different reflector or restarting the radio.

I've done a bit more digging and somebody has suggested that I should have a receive group just for the one talkgroup to fix this with this radio.
I'll test BM and see if it suits the radio better.

[AF6VN]

However, having discovered this works I decided to go back to listening on the call TG but there was nothing I could do to stop their conversation dominating my radio and Pi-Star activity. I could not get rid of them by moving channel or dialing in a different reflector or restarting the radio.

That will be a problem with any DMR system/master (actually, any MODE) -- if an active QSO doesn't leave enough time for someone to cut in (and may be compounded by an inherent delay in hot spots -- Mi-5 has a local repeater and I have two DMR HTs; with one dialed to the repeater, and the other to my hot spot, any traffic on the repeater shows up as an echo on the hot spot due to delay), it is difficult to control a hot spot. Unlike a repeater which uses separate Rx/Tx frequencies, since hot spots are simplex, if the hot spot is transmitting from the net to your radio, it won't hear your radio to respond to commands to change talk group or reflector.

I don't know enough about how your connection (Phoenix) handles reflectors -- I'd hope it only processes one at a time, so submitting a link to a different reflector would silence the currently active one. Of course, that still presumes you /can/ send the private call to change reflectors during some gap in the QSO.

It's even worse in my case... my hot spot is configured for both D-STAR and DMR modes, and a mode has to be silent for around 15-20 seconds before the other mode can be used -- the software "locks" the mode to ensure time for a response to be made in that mode. Fortunately the Pi-Star admin page offers direct commands to link/unlink D-Star, and with a registered Brandmeister account and API key, one can manipulate the active talk groups (set/remove static, drop dynamics, change reflector [not of use in US masters]).

[G6FIR]

Hi Dennis, that explanation makes a lot of sense. I'm learning so much from you, thanks again.

[N2KLC]

I am still having trouble with 2 servers configured on my mmdvm.
Everything shows up on BM and nothing is routed to DMR+ ISP2 QUADNET.

here is my Network 2 configuration:

[DMR Network 2]
Enabled=1
Address=168.235.109.210
Port=55555
TGRewrite0=2,8,2,9,1
PCRewrite0=2,84000,2,4000,1001
Password="PASSWORD"
Debug=0
Id=xxxxxxxxx
Name=DMR+_IPSC2-QUADNET
Options="TS2_83150=3150"

At times I can see I am connected to the server but no traffic is routed there.

I am specifically interested in the Vermont TG 3150 because this server does not appear to connected to the BM 3150 and A am told that VT 3150 on DMR+_IPSC2-QUADNET carries most of the Vermont traffic.


What am I doing wrong?

Thanks,
Jim
N2KLC