AnRegs
2020-11-25, 07:20 AM
Hi all!
I am involved in ham project. I am working on long range TETRA DMO-Repeater communications. What mean long range in case of TETRA DMO? It's any DMO communication longer than 5 km. LOL. Yes, just above 5 km. It doesn’t look like a record for LMR, but it’s a serious achievement for TETRA DMO that usually can’t reliably cover 2 km radius.
Why we stick with TETRA DMO? Because the idea sounds amazing! One frequency, no duplexer needed, good (a-la natural; better than DMR and P25) voice quality, small and nifty terminals. Often can be obtained for a grab price, like $100.
We installed a few of DMO repeaters in the city. They have very good conditions, like 50-70 meters’ height towers installed on 200+ meters height above sea level. 7-8 dB base antennas, 5-10 meters’ height masts with a good feeder. RF PO was set to the HW maximum (10W). One 4” cavity was used to prevent possible interference from other sites (full RF path loss is near 3-4 dB).
And I see no reasons why 2 of TETRA DMO BS cannot talk up to theoretical limit of 58 km (or something like this). But they cannot show even 25 km! Any other digital standard, like DMO or P25, will show you 15 km+ coverage with portables and 40-70 km+ with mobiles (even when BS RF power limited to 10W).
But the problem is that TETRA DMO shows only 5-10 km even when other radio is 10W base station! After 10 km radio link fails in the most of cases. And it fails NOT for signal strength reason! RSSI can be -70-80 dBm, but link fails. You have 25-30 dB margin, but radios can't talk. You can switch to DMR or P25 and get link that 2-3 times longer than TETRA DMO link (with the same antennas and power output).
All looks like TETRA standard is very complex and something happens with it making the link impossible . It confirms by ******** gear that fails first. ******** mobile radio can fail even when only 7 far from BS and with RSSI -74 dBm. So you have a good reception, but radio falls to BS-BS mode (no repeater) immediately or shows you “LINK TO REP FAIL” message after a few seconds of comms.
We tried SELEX FC3000 and SRG3900 as repeaters. Repeaters used on their native frequencies inside the ham band. There are no frequency hacks were applied. Radios programmed properly for using DMO repeater only.
We got best results with SEPURA SRG3900 repeater, but SELEX is very close to it by coverage (but less stable and can show hangs when SEPURA terminals trying to access it). BTW, SEPURA run DMO system code Edition 1, but not v1.2-1.3.
The best terminals for SEPURA are SEPURA as well (STP8000/STP9000). As stated above, ******** MTM800E is the poorest terminals for this task. Also we tested ******** MTP8550Ex, but they didn’t show anything new (even when ‘pimped’ via LAB to the 3W of PO). Hytera PT580H is similar to any average terminal. Sadly, we run out of 800FuG/MTM5400 and cannot test them as repeater nor as mobile terminal.
We have already tried range for SEPURA firmware from 10.14 through 10.22 and wide range of ******** firmware from 5.12 to 5.14.10_. MTP8550Ex were used on very fresh FW (I believe MR19.0). But all the same.
Looks like ******** has poor interoperability or/and some specific time settings in codeplug. But differences cannot be easily located because ********, SELEX and SEPURA radios using only about 70% of settings than can be directly compared. E.g. DN208, DN209 and DN213 are missed in ********, but SEPURA has i’s own unique DN213n and DN213e parameters. And many other different parameters.
Questions:
Do you guys have your own experience with DMO-R mode? What was your personal and the best results (it case of long-range / high towers)?
Any particular tips and tricks to improve DMO-R comms, like particular timer settings?
Especially we are interested in things hidden in Moto codeplug and available through LAB mode only? They exist and can be changed, but testing of all of them will take forever.
Any special firmware to improve this mode (I know it does exist even for SELEX, because I heard about their sea experiments whey they got results up to 80-100km)?
I am involved in ham project. I am working on long range TETRA DMO-Repeater communications. What mean long range in case of TETRA DMO? It's any DMO communication longer than 5 km. LOL. Yes, just above 5 km. It doesn’t look like a record for LMR, but it’s a serious achievement for TETRA DMO that usually can’t reliably cover 2 km radius.
Why we stick with TETRA DMO? Because the idea sounds amazing! One frequency, no duplexer needed, good (a-la natural; better than DMR and P25) voice quality, small and nifty terminals. Often can be obtained for a grab price, like $100.
We installed a few of DMO repeaters in the city. They have very good conditions, like 50-70 meters’ height towers installed on 200+ meters height above sea level. 7-8 dB base antennas, 5-10 meters’ height masts with a good feeder. RF PO was set to the HW maximum (10W). One 4” cavity was used to prevent possible interference from other sites (full RF path loss is near 3-4 dB).
And I see no reasons why 2 of TETRA DMO BS cannot talk up to theoretical limit of 58 km (or something like this). But they cannot show even 25 km! Any other digital standard, like DMO or P25, will show you 15 km+ coverage with portables and 40-70 km+ with mobiles (even when BS RF power limited to 10W).
But the problem is that TETRA DMO shows only 5-10 km even when other radio is 10W base station! After 10 km radio link fails in the most of cases. And it fails NOT for signal strength reason! RSSI can be -70-80 dBm, but link fails. You have 25-30 dB margin, but radios can't talk. You can switch to DMR or P25 and get link that 2-3 times longer than TETRA DMO link (with the same antennas and power output).
All looks like TETRA standard is very complex and something happens with it making the link impossible . It confirms by ******** gear that fails first. ******** mobile radio can fail even when only 7 far from BS and with RSSI -74 dBm. So you have a good reception, but radio falls to BS-BS mode (no repeater) immediately or shows you “LINK TO REP FAIL” message after a few seconds of comms.
We tried SELEX FC3000 and SRG3900 as repeaters. Repeaters used on their native frequencies inside the ham band. There are no frequency hacks were applied. Radios programmed properly for using DMO repeater only.
We got best results with SEPURA SRG3900 repeater, but SELEX is very close to it by coverage (but less stable and can show hangs when SEPURA terminals trying to access it). BTW, SEPURA run DMO system code Edition 1, but not v1.2-1.3.
The best terminals for SEPURA are SEPURA as well (STP8000/STP9000). As stated above, ******** MTM800E is the poorest terminals for this task. Also we tested ******** MTP8550Ex, but they didn’t show anything new (even when ‘pimped’ via LAB to the 3W of PO). Hytera PT580H is similar to any average terminal. Sadly, we run out of 800FuG/MTM5400 and cannot test them as repeater nor as mobile terminal.
We have already tried range for SEPURA firmware from 10.14 through 10.22 and wide range of ******** firmware from 5.12 to 5.14.10_. MTP8550Ex were used on very fresh FW (I believe MR19.0). But all the same.
Looks like ******** has poor interoperability or/and some specific time settings in codeplug. But differences cannot be easily located because ********, SELEX and SEPURA radios using only about 70% of settings than can be directly compared. E.g. DN208, DN209 and DN213 are missed in ********, but SEPURA has i’s own unique DN213n and DN213e parameters. And many other different parameters.
Questions:
Do you guys have your own experience with DMO-R mode? What was your personal and the best results (it case of long-range / high towers)?
Any particular tips and tricks to improve DMO-R comms, like particular timer settings?
Especially we are interested in things hidden in Moto codeplug and available through LAB mode only? They exist and can be changed, but testing of all of them will take forever.
Any special firmware to improve this mode (I know it does exist even for SELEX, because I heard about their sea experiments whey they got results up to 80-100km)?