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Thread: Long range TETRA DMO-R links. Issues, tips and tricks.

  1. #1
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    Exclamation Long range TETRA DMO-R links. Issues, tips and tricks.

    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 Motorola gear that fails first. Motorola 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, Motorola MTM800E is the poorest terminals for this task. Also we tested Motorola 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 Motorola 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 Motorola has poor interoperability or/and some specific time settings in codeplug. But differences cannot be easily located because Motorola, SELEX and SEPURA radios using only about 70% of settings than can be directly compared. E.g. DN208, DN209 and DN213 are missed in Motorola, but SEPURA has i’s own unique DN213n and DN213e parameters. And many other different parameters.

    Questions:


    1. 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)?
    2. Any particular tips and tricks to improve DMO-R comms, like particular timer settings?
      1. 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.

    3. 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)?

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  4. #2
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Dear friend,

    I can describe to you the experience of the local disaster relief and dog rescue service.
    We have three tetra DMO repeaters. All Cleartone-Motorola.
    One is fix base repater with a piece of CM-9000 set to 8Watt transmit power, with a 10 meter H-2000 coaxial cable, with an 8dBd (10.2dBi) gain antenna over the city (Tatabánya city in Hungary).
    Operating mode 1B, duplex distance 1.6MHz.
    It is on the side of a mountain, so we have a good coverage.
    Where the CM-9000 repeater can't see it even a little bit, we can't use it anymore!
    Our terminals are only handhealds, there is no mobile radio that can be installed in a car.
    Motorola MTH-800, MTP-850S, they have a long 11cm antenna, Sepura SRH handsets with 8cm antenna and EADS THR-9i radios.
    We also have 2 CM5000 DMO repeaters, these are used in relocations.
    They are tuned to 12W, we install an 8dBd gain antenna with a low loss cable on a 6 meter long telescopic mast.

    My experience with a base repeater on a hill above the city:
    Where the repeater can see, inside the city, there is the worst signal level of -78dBm.
    The maximum distance from which we used the system with hand-held radios:
    30km distance.
    Pusztavám city (you can search on Google maps Tatabánya - Pusztavám distance and terrain too).

    Our problems:
    Slow call setup.
    Where the system is only slightly visible, it is impossible to transmit or connect to the system.

    The positives:
    Where the system can see, with only a signal level of -93dBm, from a distance of 30km we can use them with simple handheald terminals.
    Excellent voice quality.

    Projects:
    Upgarde the CM5000's above FW 1.07 to pass through the private calls, becouse below FW 1.19 private call through DMO repeater is not supported.
    Interlink the two CM5000's as in Wienna, Austria (great article about it: https://blog.wq.lc/how-to-link-two-svxlink-repeaters/ ).

    I wish you a pleasant day and good health!
    Gábor from Tatabánya, Hungary.
    Last edited by 580-Gabor; 2020-11-25 at 09:11 PM

  5. #3
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Hi Gabor!

    Operating mode 1B, duplex distance 1.6MHz.
    Thanks for your feedback. But could you please decipher what is the duplex distance? I think that you meant duplex space or duplex shift (1.6 MHz), but how it's possible in TETRA DMO? Because the same frequency is used for RX and TX. There are no duplex space (shift).

    Where the CM-9000 repeater can't see it even a little bit, we can't use it anymore!
    What's happened to it? It's unclear from your statement.

    Motorola MTH-800, MTP-850S, they have a long 11cm antenna, Sepura SRH handsets with 8cm antenna
    Which frequencies are you using with these radios? Approximately, e.g. 410-420 MHz.

    Where the system can see, with only a signal level of -93dBm, from a distance of 30km we can use them with simple handheald terminals.
    It's very good result. In my case if RSSI is below -90 dBm, I only can 'see' repeater, or try to get into it, but voice will not pass at through repeater all. To let voice pass through I need to get RSSI like -78...-85. And use 1/4L handheld antenna in static position (no moves). So your result looks better, but you're using different repeaters.

    Soon I will test CM-9000 at the same position and will improve pre-selector with 10" cavity of 3/4 length. I will share my results.

    P.S.
    Have a nice day too. Take care.
    Last edited by AnRegs; 2020-11-26 at 01:38 AM

  6. #4
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Hi

    there are various modes for DMO repeaters :

    DMR Repeater.jpg

  7. #5
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Hi!

    Good to know. I was too lazy to read about 1B.

    Gabor,

    Which mode are you using? 1A or 1B? Of course, I am talking about 1A (one frequency).

  8. #6
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Hi all!

    Stupid question. What hardware supports 1B repeater mode (uses duplex spacing)?

    I googled a lot, played with RM2 and Moto CPS, and found no mentions about 1B mode. Also, I found some interop test reports, and looks like 1B mode was not tested for Moto and SEPURA. Is it not implemented?

    I found only proofs of 1B support for CLEARTONE CM5000.

    I am not sure about CM9000. One of files has describes this mode, but official CLEARTONE's papers has nothing on this. Also, I see no 1A/1B mentions in Native Programming software (but to be honest, I looked quickly and have never used CLEARTONE; So I admin I can overlook it).

    But what else?

  9. #7
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Hi there,

    Cleartone CM5000 can do 1A and 1B, all versions have 5W output power, but it is easy and secure adjustable to 12W, it is fullband and extendable from 375-435MHz.
    Cleartone CM9000 can only do 1B (no 1A support), there are 3W and 10W versions and are not "fullband" (eg 380-400MHz government version).
    Most important: not all terminals supports 1A connecting (some older terminals can't connect to 1A repeaters).
    So we are using the good old 1B version, it reduces the potential RF interference too.

  10. #8
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    We are using only 1B, 1,6MHz (as in Germany) with the CM5000 repeaters,
    and 4,5 or 8MHz with the CM9000 terninals.
    (CM9000 working only as 1B repeater. With bigger duplex space it is "faster").
    Last edited by 580-Gabor; 2020-12-08 at 05:18 PM

  11. #9
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Can you confirm that CM9000 can't do 1A mode?

  12. #10
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    Default Re: Long range TETRA DMO-R links. Issues, tips and tricks.

    Yes.
    No 1A in the CM9000
    http://www.oppermann-telekom.de/cm9000.html
    I have three of them (2x3W version, 1x10W version).

    (The Nokia THR-4, older THR-880 devices cant work through 1A repaeaters too)

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