DMR Repeater Talk-Around

Status
Not open for further replies.

chief21

Member
Premium Subscriber
Joined
Mar 2, 2004
Messages
1,469
Location
Summer - Western NC; Winter - Tampa Bay FL
I've recently been following a thread on the MD-380 Yahoo group regarding the fact that the Repeater Talk-Around function (T/A) apparently does not work on the TYT MD-380 and its variants. More precisely, a radio monitoring a particular DMR repeater channel/talkgroup will not receive any signal from another radio on the same repeater channel/talkgroup operating in T/A (direct) mode. Direct radio-to-radio comms are possible only if BOTH radios are set to T/A mode by advance arrangement.

At least one other person has reported that the T/A function does work as expected on major-brand DMR radios (Motorola, Hytera, etc).

I'm curious if these statements are accurate and if so, is this a well-known issue?

Additionally, is the issue limited only to chinese radios and is it possible that it could be resolved by a current or future firmware upgrade?

Thanks in advance for any insights.

John AC4JK
 

Raccon

Member
Joined
Mar 1, 2005
Messages
408
If Hytera radios work, how can it be an issue limited to Chinese radios?
 

com501

Member
Joined
Sep 28, 2003
Messages
1,365
Location
127.0.0.1
One should NEVER use talkaround on a repeater frequency. 2-slot DMR does not support talkaround when a repeater shares the same frequency. The repeater ALWAYS supplies the timing for 2-slot operation. A simplex radio will interfere with BOTH slots on the repeater as it's timing is not in alignment with the repeater. MotoTrbo radios and some other manufacturers have 2-slot simplex in their newer offerngs. HOWEVER, the mobiles will use their own timing for that funcstion, not that of the repeater.

Talkaround is not recommended in the system planner for that reason.
 

JRayfield

Member
Joined
Jul 31, 2009
Messages
797
Location
Springfield, MO
Sometimes, a person may want to use Talkaround, if the repeater is 'down' (off). And then it is very good if the radios that are still set to the 'repeater channel' can receive a unit that is transmitting in T/A mode. And the Motorola radios will do that.

John Rayfield, Jr.

One should NEVER use talkaround on a repeater frequency. 2-slot DMR does not support talkaround when a repeater shares the same frequency. The repeater ALWAYS supplies the timing for 2-slot operation. A simplex radio will interfere with BOTH slots on the repeater as it's timing is not in alignment with the repeater. MotoTrbo radios and some other manufacturers have 2-slot simplex in their newer offerngs. HOWEVER, the mobiles will use their own timing for that funcstion, not that of the repeater.

Talkaround is not recommended in the system planner for that reason.
 

N4GIX

Member
Premium Subscriber
Joined
May 27, 2015
Messages
2,011
Location
Hammond, IN
Er, "Talkaround" takes place on the output frequency of the repeater, not the input frequency. Therefore it will not "interfere" with the repeater's timing since it's not keying up the repeater...
 

buddrousa

Member
Premium Subscriber
Joined
Jan 5, 2003
Messages
8,938
Location
NW Tenn
In talkaround mode the radio is looking for DMR no time slot. I have played with my MD380's and it will not receive the repeater which is DMR tier 2 because the radio is in DMR tier 1 if this make sense to you.
 

N4KVE

Member
Joined
Mar 1, 2003
Messages
3,487
Location
PALM BEACH, FLORIDA
Motorola, & Hytera radios will talk to each other on the output of a repeater channel. When a bunch of us guys go out of town to a small Hamfest, we go to our local repeater freq which is out of range, & use talk around on our repeater freq. The reason this affects all Chinese radios except Hytera is because all CCR's use the same consulting company to write their CPS.
 

com501

Member
Joined
Sep 28, 2003
Messages
1,365
Location
127.0.0.1
Just DO NOT use talkaround when in the repeater coverage area. And -duh, I know T/A is on the repeater output and not the input, but you WILL interfere with repeater ops if anyone else is using the repeater.

If you use talkaround in my repeater's coverage area on the output, and the site is NOT down, I will ban your ID from my system.

Not a single radio that leaves our shop gets T/A on Trbo systems. Even the customers with 4k-8k radios.
 

Ghstwolf62

Member
Premium Subscriber
Joined
May 23, 2006
Messages
1,352
Location
Clifton Forge Virginia
There are national simplex freqs for that and they should be used. There was a big discussion about this a couple of years back and it had something to do with somehow being on TA on the repeater output messed with the repeater. Don't ask me to explain it just take it as a big no no.

Lot of tech talk but just not a good idea. Program the national simplex channels in and use them if you want TA capability. TG 99 is the standard.
 

N4GIX

Member
Premium Subscriber
Joined
May 27, 2015
Messages
2,011
Location
Hammond, IN
TA on amateur repeater frequencies is totally unnecessary to begin with. It really shouldn't even be an option. That's what simplex frequencies are for.

For fixed frequency PS and business use however, TA would only be potentially desirable if for some reason the repeater(s) were down.
 

notwenif

Member
Joined
Feb 21, 2010
Messages
5
Location
Elkhart Indiana
Just DO NOT use talkaround when in the repeater coverage area. And -duh, I know T/A is on the repeater output and not the input, but you WILL interfere with repeater ops if anyone else is using the repeater.

If you use talkaround in my repeater's coverage area on the output, and the site is NOT down, I will ban your ID from my system.

Not a single radio that leaves our shop gets T/A on Trbo systems. Even the customers with 4k-8k radios.
You are wrong. T/A is quite simply, well...simplex. using talk around will NOT interfere with repeater operation.
 

kc9bxx

Member
Joined
Oct 30, 2004
Messages
23
Location
steuben County indiana
To get onto original topic. I have a MD390 and a CS800. The TA works, on both, however you have to have both radios on TA, if only one radio is in TA then you will only see signal on your meter, but no audio.

and anyone involved with emergency communications should know the benefits on TA, if you do not then I think you should reeducate yourself with the benefits.
 

chief21

Member
Premium Subscriber
Joined
Mar 2, 2004
Messages
1,469
Location
Summer - Western NC; Winter - Tampa Bay FL
That's how mine work as well... but it's not true talk-around. IMHO, one of the best features of TRUE talk-around is the ability to be able to communicate with other units in the event that, for whatever reason, contact with the repeater is lost without notice.

Example: My friend is parked nearby, monitoring a repeater channel. I have gone into a building to retrieve something. Due to the type of building, I am no longer able to reach the repeater but need to contact my friend outside (who is unaware that I am unable to reach the repeater). With true talk-around, I would be able to contact him directly, via talk-around (without any pre-arrangement), and have him switch to talk-around (or another frequency) to re-establish 2-way communication. (a simplistic example, I know.)

When using some DMR radios, as you mentioned, talk-around can only be used "with notice" or by pre-arrangement... not in a circumstance like I have described.

John

To get onto original topic. I have a MD390 and a CS800. The TA works, on both, however you have to have both radios on TA, if only one radio is in TA then you will only see signal on your meter, but no audio.
 
Last edited:

N4KVE

Member
Joined
Mar 1, 2003
Messages
3,487
Location
PALM BEACH, FLORIDA
When using some DMR radios, as you mentioned, talk-around can only be used "with notice" or by pre-arrangement... not in a circumstance like I have described.
Exactly. Everybody I know has some prearranged simplex freq's in their radios to talk to their wives, or unlicensed friends in simplex at the mall. So John's 3 radios can talk to each other, & Mike's 3 radios can talk to each other, & Bob's 3 radios can talk to each other. BUT, John, Mike, or Bob's radios can not talk to each other. Too many different freq's, CC's, & TG possibilities. But when John, Mike, & Bob are in a situation where they need to talk to each other in simplex mode, they all have the same local repeater in their radios, & the T/A mode on the output of the repeater is common to all their radios. When some locals drove 150 miles to the Tampa ham fest, where our repeater was out of range, the only common freq in our radios was the Miami repeater. Since that freq was not in Tampa, we pushed the T/A button, & spoke to each other. Since we all use Motorola radios, T/A worked just fine. I can assure you none of my simplex freq's in my radios are in my friend's radios. Same with them.
 

Citywide173

Member
Premium Subscriber
Joined
Feb 18, 2005
Messages
1,947
Location
Attleboro, MA
You are wrong. T/A is quite simply, well...simplex. using talk around will NOT interfere with repeater operation.
This is the way I understand what those saying it will interfere with repeater operations are saying:

When you are using a DMR radio on simplex, it creates it's own timing that will most likely be in conflict with the repeater's timing, meaning that if there is a user using the repeater within range of the person on simplex, there will be a timing conflict created and it WILL interfere with repeater operations, at least for the repeater users in range of the simplex operator.
 

kc9bxx

Member
Joined
Oct 30, 2004
Messages
23
Location
steuben County indiana
That's how mine work as well... but it's not true talk-around. IMHO, one of the best features of TRUE talk-around is the ability to be able to communicate with other units in the event that, for whatever reason, contact with the repeater is lost without notice.

Example: My friend is parked nearby, monitoring a repeater channel. I have gone into a building to retrieve something. Due to the type of building, I am no longer able to reach the repeater but need to contact my friend outside (who is unaware that I am unable to reach the repeater). With true talk-around, I would be able to contact him directly, via talk-around (without any pre-arrangement), and have him switch to talk-around (or another frequency) to re-establish 2-way communication. (a simplistic example, I know.)

When using some DMR radios, as you mentioned, talk-around can only be used "with notice" or by pre-arrangement... not in a circumstance like I have described.

John
You are right, apparentaly I misread some of the words in the origional post. :) Thank you, I do agree that
TA is not as easy on DMR as analog, but I guess that is where having a communications plan pays off.
 

IAmSixNine

Member
Feed Provider
Joined
Dec 19, 2002
Messages
2,103
Location
Dallas, TX
May not be the best or easiest option. But if you have a device (all of some of them) that does not pick up TA on the same frequency as the repeater out it may be helpful to program a different channel as the TA you want.
Then create multiple scan lists. Match the scan lists to the repeater channel you are currenty using and add the corresponding talk around channel.
So add all 4 of the national direct channels, then the couple you and your group use plus the direct / out put of the repeater your using.

Example, where i am in dallas we have 2 as metro, 3148 as texas state wide.
If im sitting on 2, i would have it scan that channel from repeater, have the 4 nationwide channels and the 2 direct as well.
I also have a different channel with multiple TG plus the directs. Sure it takes a bit more time programming but if direct doesnt work like it does with analog then we as users have to adjust as well.
Just my 2 cents.
 

notwenif

Member
Joined
Feb 21, 2010
Messages
5
Location
Elkhart Indiana
This is the way I understand what those saying it will interfere with repeater operations are saying:

When you are using a DMR radio on simplex, it creates it's own timing that will most likely be in conflict with the repeater's timing, meaning that if there is a user using the repeater within range of the person on simplex, there will be a timing conflict created and it WILL interfere with repeater operations, at least for the repeater users in range of the simplex operator.
In Talk Around mode a Tier-2 DMR system the simplex characteristics are quite similar to standard analog or conventional simplex operation. that is, their is only one voice path available in 12.5khz spacing during talk-around mode. Whereas the repeater and only the repeater performs the "Slotting" or FDMA timing which affords 2 voice paths in the same allotted bandwidth.

I understand the theory of repeater output interference. However, in the DMR world this has not been verified. Quite simply, if using talk-around on the output frequency of a repeater causes interference, then stop. As to the best of my knowledge, no rules exist governing talk-around in this manner.
 

kayn1n32008

ØÆSØ
Joined
Sep 20, 2008
Messages
6,303
Location
Sector 001
In Talk Around mode...their is only one voice path available in 12.5khz spacing during talk-around mode. Whereas the repeater and only the repeater performs the "Slotting" or FDMA timing which affords 2 voice paths in the same allotted bandwidth.
This is not accurate.

some radios are capable of 2 slot simplex operation. there is also some radios that can act as a repeater on a somplex channel as well.
 
Status
Not open for further replies.
Top