DMR: Need Some Help Understanding

[Colin9690]

I'm looking for some help understanding what type of DMR this system is using, and how to program it into my SDS-100. It's not yet in the database, and I'm intending to submit it to the database when I get this figured out. The system in question is: Worthington City Schools.

On my first programming attempt I created the system, entered all of the frequencies listed, and set the "System Type" as "MotoTRBO Trunk". I made sure that the ID Search is ON. When I scan the system, I hear nothing. Using my SDS-200, I parked it on 152.420 and I hear voice loud and clear, and the DMR icon toward the top right of the screen flashes. So I obviously don't have the system programmed correctly, as I hear nothing when I scan it as a MotoTRBO Trunk system and my other scanner is picking up voice on one of the frequencies at the same time.

I attached a PDF of my results of monitoring the entire system for a day, using Proscan. Per advice in the Wiki I set up a favorites list containing all the system frequencies, and programmed the system as conventional (since I don't know what type of DMR this is). The only other option for programming it is "DMR One-Frequency". Looking at the attached spreadsheet of the results, they are using at least 2 different frequencies (I assume 157.680 is an input frequency?). It doesn't make sense to me for this to be DMR One-Frequency, if they are using more than one frequency.

Two more things -- it should be noted that I heard a user transmitting on 152.420 say "switch to Channel 2". I then picked them up on 160.200, using a different color code (as shown in the PDF). Lastly, I'm curious as to why some transmissions on 152.420 don't have an associated slot number. Most of the transmissions are using slot 1 or 2 (152.420/1), but there are several at the top of the page with no slot indication.

I would appreciate any pointers or insight. I confess that I am somewhat new to monitoring DMR, this is the first time I've tried to submit a DMR system to the database. I apologize if there's something simple I've overlooked.

 

[rf_patriot200]

I'm looking for some help understanding what type of DMR this system is using, and how to program it into my SDS-100. It's not yet in the database, and I'm intending to submit it to the database when I get this figured out. The system in question is: Worthington City Schools.

On my first programming attempt I created the system, entered all of the frequencies listed, and set the "System Type" as "MotoTRBO Trunk". I made sure that the ID Search is ON. When I scan the system, I hear nothing. Using my SDS-200, I parked it on 152.420 and I hear voice loud and clear, and the DMR icon toward the top right of the screen flashes. So I obviously don't have the system programmed correctly, as I hear nothing when I scan it as a MotoTRBO Trunk system and my other scanner is picking up voice on one of the frequencies at the same time.

I attached a PDF of my results of monitoring the entire system for a day, using Proscan. Per advice in the Wiki I set up a favorites list containing all the system frequencies, and programmed the system as conventional (since I don't know what type of DMR this is). The only other option for programming it is "DMR One-Frequency". Looking at the attached spreadsheet of the results, they are using at least 2 different frequencies (I assume 157.680 is an input frequency?). It doesn't make sense to me for this to be DMR One-Frequency, if they are using more than one frequency.

Two more things -- it should be noted that I heard a user transmitting on 152.420 say "switch to Channel 2". I then picked them up on 160.200, using a different color code (as shown in the PDF). Lastly, I'm curious as to why some transmissions on 152.420 don't have an associated slot number. Most of the transmissions are using slot 1 or 2 (152.420/1), but there are several at the top of the page with no slot indication.

I would appreciate any pointers or insight. I confess that I am somewhat new to monitoring DMR, this is the first time I've tried to submit a DMR system to the database. I apologize if there's something simple I've overlooked.

I'm guessing Uniden's way of interpreting Tier 3, is no slot shown in which Both timeslots are used . My old High School & district does something similiar on 852 mhz. on Dmr.

 

[Ubbe]

the DMR icon toward the top right of the screen flashes.

Then it's a conventional DMR channel and not trunked. It should says CAP or D3 if it's trunked. If you park on a channel doing Channel+frequency+Channel it will decode all signals and indicate what type of system it is if you park on the control channel. If can't hear any control channel idle data bursts then it's for sure a conventional system.

Lastly, I'm curious as to why some transmissions on 152.420 don't have an associated slot number. Most of the transmissions are using slot 1 or 2 (152.420/1), but there are several at the top of the page with no slot indication.

Unidens DMR scanners are not 100% reliable in their decode accuracy. You can see that as it sometimes also indicates CC4 and CC10 when it is a CC1 channel.

Sometimes when a radio shop installs a simple DMR system that replaces an old analog one they simply use each time slot as the old analog channel and put a TG on each slot that mimics the old CTCSS code. It's just a way of switching to modern equipment without taking advantage of its (more complicated to configure) trunking capabilities.

If you force a scanner to analog mode and listen to a DMR channel and you hear a constant data flow then it is a repeater but if you hear it using only one timeslot with a 20Hz chopping it is a simplex or the input frequency of the repeater you are monitoring. A SDS scanner would normally not unmute on a single slot transmission in analog mode due to the squelch acting too slow so you'll need to set that to 0.

/Ubbe

 

[Colin9690]

Then it's a conventional DMR channel and not trunked. It should says CAP or D3 if it's trunked. If you park on a channel doing Channel+frequency+Channel it will decode all signals and indicate what type of system it is if you park on the control channel. If can't hear any control channel idle data bursts then it's for sure a conventional system.


Unidens DMR scanners are not 100% reliable in their decode accuracy. You can see that as it sometimes also indicates CC4 and CC10 when it is a CC1 channel.

Sometimes when a radio shop installs a simple DMR system that replaces an old analog one they simply use each time slot as the old analog channel and put a TG on each slot that mimics the old CTCSS code. It's just a way of switching to modern equipment without taking advantage of its (more complicated to configure) trunking capabilities.

If you force a scanner to analog mode and listen to a DMR channel and you hear a constant data flow then it is a repeater but if you hear it using only one timeslot with a 20Hz chopping it is a simplex or the input frequency of the repeater you are monitoring. A SDS scanner would normally not unmute on a single slot transmission in analog mode due to the squelch acting too slow so you'll need to set that to 0.

/Ubbe

Thank you for the explanation, much appreciated.

 

[BinaryMode]

Unidens DMR scanners are not 100% reliable in their decode accuracy. You can see that as it sometimes also indicates CC4 and CC10 when it is a CC1 channel.

QFT

Same for P25. I've tried to change decode threshold (available for DMR ass well) so many times! When mobile it's a PITA. At home there's no issue.

 

[serial14]

Unidens DMR scanners are not 100% reliable in their decode accuracy. You can see that as it sometimes also indicates CC4 and CC10 when it is a CC1 channel.

I agree here. I see this manifest sometimes stopping on the channel, but not decoding the various parameters of the DMR transmission. The scanner just sits there blank. I've also seen where the CC changes with erroneous decodes.

In these circumstances, I've found good gains in increasing the performance/gain/type of antenna I'm using. Increasing the SNR helps the SDS200 a good amount in speed and accuracy of the decode. This is usually easier said than done. As an example, there is a DMR system I listen to when on travel. On an OEM telescoping whip, I can hear the signal but get erroneous decodes. When I change over to a band specific whip or use my travel ground plane, the decode performance increases a lot.

 

[Ubbe]

Increasing the SNR helps the SDS200 a good amount in speed and accuracy of the decode.

Yes, that goes for all Uniden models as they reuse the same kind of code in the firmware. There's some fundamental wrong with the error correction routine in the firmware and will show when there is a weak signal with lots of data errors that needs to be corrected by the forward error correction method. When RAS are detected in a system the error correction needs to be disabled, so it seems that it false detect RAS that makes it decode the data much worse and it will then also false detect encryption that will skip the channel. I hope that Uniden comes out with a firmware upgrade, as promised by JoeBearcat, that correct this behavior.

/Ubbe

 

[BinaryMode]

I hope that Uniden comes out with a firmware upgrade, as promised by JoeBearcat, that correct this behavior./Ubbe

Any chance that happening with the P2's?

 

[16b]

I'm looking for some help understanding what type of DMR this system is using, and how to program it into my SDS-100. It's not yet in the database, and I'm intending to submit it to the database when I get this figured out. The system in question is: Worthington City Schools.

On my first programming attempt I created the system, entered all of the frequencies listed, and set the "System Type" as "MotoTRBO Trunk". I made sure that the ID Search is ON. When I scan the system, I hear nothing. Using my SDS-200, I parked it on 152.420 and I hear voice loud and clear, and the DMR icon toward the top right of the screen flashes. So I obviously don't have the system programmed correctly, as I hear nothing when I scan it as a MotoTRBO Trunk system and my other scanner is picking up voice on one of the frequencies at the same time.

I attached a PDF of my results of monitoring the entire system for a day, using Proscan. Per advice in the Wiki I set up a favorites list containing all the system frequencies, and programmed the system as conventional (since I don't know what type of DMR this is). The only other option for programming it is "DMR One-Frequency". Looking at the attached spreadsheet of the results, they are using at least 2 different frequencies (I assume 157.680 is an input frequency?). It doesn't make sense to me for this to be DMR One-Frequency, if they are using more than one frequency.

Two more things -- it should be noted that I heard a user transmitting on 152.420 say "switch to Channel 2". I then picked them up on 160.200, using a different color code (as shown in the PDF). Lastly, I'm curious as to why some transmissions on 152.420 don't have an associated slot number. Most of the transmissions are using slot 1 or 2 (152.420/1), but there are several at the top of the page with no slot indication.

I would appreciate any pointers or insight. I confess that I am somewhat new to monitoring DMR, this is the first time I've tried to submit a DMR system to the database. I apologize if there's something simple I've overlooked.

The system you're monitoring is already in the RR database as a Capacity Plus system, although it looks like it hasn't been touched in six years so it's entirely possible that something has changed. However, the log that you posted does seem (to me) to be consistent with the system as documented in the database. It looks like the FCC license has six mobile-only frequencies; three of those are going to be input for the three repeaters, which leaves three that are possibly used for simplex. 160.200 "channel 2" might be one of those. It's common for school bus radios to have a simplex channel for bus-to-bus communications on trips outside of the school district where the repeater doesn't cover. Also, I would expect the scanner's ability to decode things like color code and talkgroup IDs to be flaky on weak signals, which is more likely when you're listening to a mobile user on a simplex frequency or a repeater input. I wouldn't trust those color code values until you've monitored them consistently several times.

See Worthington City Schools Trunking System, Worthington, Ohio

 

[Colin9690]

The system you're monitoring is already in the RR database as a Capacity Plus system, although it looks like it hasn't been touched in six years so it's entirely possible that something has changed. However, the log that you posted does seem (to me) to be consistent with the system as documented in the database. It looks like the FCC license has six mobile-only frequencies; three of those are going to be input for the three repeaters, which leaves three that are possibly used for simplex. 160.200 "channel 2" might be one of those. It's common for school bus radios to have a simplex channel for bus-to-bus communications on trips outside of the school district where the repeater doesn't cover. Also, I would expect the scanner's ability to decode things like color code and talkgroup IDs to be flaky on weak signals, which is more likely when you're listening to a mobile user on a simplex frequency or a repeater input. I wouldn't trust those color code values until you've monitored them consistently several times.

See Worthington City Schools Trunking System, Worthington, Ohio

Thank you for the reply and insight. If i remember correctly, I think I was the one that submitted that system years ago. The only reason that lead me to think it wasn’t Capacity Plus was the fact my SDS was always flashing DMR during active transmissions (not CAP +). Thank you for helping me understand. I’ve been using all sorts of scanners since I was 13 and thought i understood everything. But DMR is the one that I can’t seem to wrap my head around yet. 👍