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Thread: Linking two Quantars in P25 mode Over IP

  1. #1
    ev351 No Longer Registered

    Default Linking two Quantars in P25 mode Over IP

    Hi all, I have been hunting around for the most cost effective ( Tight ***) way of linking two Quantars in P25 mode over IP. I don't care about analog. I am struggling to get any good results from searching things like link qauntars ip etc etc. If anyone has any info on the most straight forward way to achieve this it would be greatly appreciated. There is nothing special like simulcasting or voting involved, just two diffrerent bases linked together on different frequencies over and IP network. If only it was TRBO. Ev.


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    The Quantars (and all ASTRO generation Motorola P25 gear) uses V.24 Synchronous Serial 9600 RS232 comms. You need something that will do V.24 over IP.

    Unfortunately this requires Telco grade gear which isn't cheap.

    Are you looking to do this over the internet? or leased line? or ATM over fibre etc?

    Cheers,
    Matt

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    ev351 No Longer Registered

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    HI Matt, It would be preferable to use the internet for the link path. I did say tight *** I know that you can use Astro Modems to link them together, but they need 4 wire audio do they not? I wonder can that be directed over IP at a better cost? Ev.

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    I use a V.24 daughterboard on the wireline card, to interface with a DIU3000. The DIU3000 is then interfaced with an IRLP (www.irlp.net) server. I can patch to any other IRLP server.

    But this doesn't sound as good as it could and embedded digital signalling isn't preserved. This is why I've decided to move away from Quantars/IRLP and adopt TRBO for my needs. The Quantar (and P25 in general) is not easily linked to other machines with reasonable budgets. If I was you, I'd seriously consider dropping P25 and going TRBO. You also get two talk-paths with TRBO and audio quality (depending on opinion) is slightly better, due to the AMBE+2 codec.

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    cyrus's Avatar
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    I believe you could use v.24 to Ethernet asynchronous converters.

    The only problem is finding someone who's done it because not all converters work.
    Cyrus

    Bubbles: I'd like to see that Red Blue Green c***sucker put one of those together, duct-tapin' it.

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    ev351 No Longer Registered

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    THanks for the replies. Do you mean Syncronous converters Cyrus? If not, then it would be fairly easy, but if you do mean syncronous, then from what io can see it can be pricey and difficult.

    Mars, Yes, we are indeed thinking TRBO, I have been messing about with it, and its just so easy to link with ip.. shame about all the astro gear that will go to waste...

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    Nope, pretty sure you need asynchronous v.24.

    Prices on EBay seem to be a few hundred dollars each. Too much money for me to take a chance on something which might or might not work.
    Cyrus

    Bubbles: I'd like to see that Red Blue Green c***sucker put one of those together, duct-tapin' it.

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    syntrx No Longer Registered

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    The quality of the link will be an issue even once you get the hardware. Jitter will apparently upset it pretty quickly.

    Private IP (or commercial connectivity with QoS) will be OK. Internet will probably be problematic.

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    Quantars are 100% synchronous v.24 - I have checked this on a DSO and all the clock lines are all active and in use.

  10. #10
    ev351 No Longer Registered

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    I thought as much... that pretty much makes it a no go over the net..... which is a shame.. Its been a great ride P25.... but maybe its time to move on. Its just so straight forward with TRBO.

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    This looks interesting - http://www.advancedrelay.com/ci/products/products

    These guys develop synchronous serial adaptors that can work over ethernet, IP or USB.. maybe theres some potential there..

  12. #12
    syntrx No Longer Registered

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    Circuit emulation over IP on Cisco routers is an option. I work in the banking industry, we used to do this a lot for legacy ATMs and other systems before we finally got rid of all that old ****.

    http://www.cisco.com/en/US/docs/ios/.../bbfeamod.html

    The routers themselves are cheap, but the NM-CEM-4SER module you need to do CEoIP with synchronous serial lines is not common, and is therefore hard to find at a reasonable price.

    Think minimum $600 per end using a 3640 or similar and one of these modules, but the cool thing is you can do analog voice on the same equipment if you add voice cards, if you're running a mixed mode system. Probably need a 3800 series router to do "proper" LMRoIP, which will add to the cost.

    An alternative might be to pick up a couple of old sun4m SPARCstations with the Zilog 8530 SCC (which does synchronous V.24 and HDLC in hardware), and write your own software to haul the data across from one box to another. Hardware wise for this you'd be looking at $30 per end, assuming your time has no value.

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    I have a side plan to use a Zilog 8530 SCC with an Atmel AVR and an ethernet module as another idea..

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    Maybe forget about the Z8530 try the Open HDLC project:

    http://sourceforge.net/projects/opensourcehdlc/

    This can be run on a PC and I think the parallel port will be fast enough. Another option is one of the small microcontroller boards with an Ethernet port, the Ardinuo is probably too slow so a Cortex or similar is in order as the sync port is emulated software. The PC will be cheaper. Also you don't need the V.24 daughter board as a 50 pin two row header can be pushed into the socket on the Wireline card and the necessary TTL level signals picked up. Will post a bunch more when I can get to a PC instead of a tablet.
    Last edited by Astro Spectra; Dec 13, 2012 at 05:12 AM.

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    The trick for networking multiple Quantars together is to first lean down the HDLC traffic before sending over IP as UDP so you're not wasting bandwidth just keeping the link up (necessary for linking over the Internet, not necessary for point to point over unlicensed radio).

    Each Quantar directs UDP packets to a central server that emulates a single DIU or Quantar to each connected Quantar. In the background the server replicates LDU frames received to all the other Quantars. Kind of a Quantar version of IP site connect... A high level overview but you get my drift.

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    Yes - thats kind of the idea but I need to see more whats going on inside the HDLC frames first..

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    Just a quick comment on CEoIP you need to keep the buffers very small. A 512 byte buffer will introduce an unacceptable delay in the audio of more than a half second.

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    Maybe time for a new thread to share the learning...

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    Let's say you have two Quantars in the same rack.. would a straight-through serial connection get you linked in P25 and analog, or just P25? If there's a tutorial out there for the specific hardware connections and programming configuration necessary I wouldn't mind reading it.

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    The serial V.24 port will only give you P25 ASTRO linking. To do analog you need to hook them up using the wireline interface on the back or the 50 pin telco connector will also have the required connections.

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    Gotcha, thanks. That sure makes trying to get v.24 connectivity at remote sites less appealing.

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    Config for two co-located stations is as follows:

    Join CTS to RTS on each station and then jumper over to the CD on the other station. So when the Quantar wants to send (RTS) it gets the OK (CTS) and the other station sees carrier detect.

    TXD crosses over to RXD on the other station - obvious.

    Now in Win RSS go to Wireline Config, Wireline and set Astro to Wireline to Enabled (can't remember if that's required).

    Now decide which station is 'master', not critical but don't choose one that might get turned off. Connect the master's TDCLK to master's RXDCLK, and to slave's RXDCLK.

    Now on Wireline Config, Astro set Wireline Interface to V.24 Only and set the master's External Transmit Clock to disabled and the slave's External Transmit Clock to disabled. On same screen set RT/RT config to enabled.

    If the stations are linked via a V.24 circuit over microwave or telco then the clock wiring and settings will need to be changed to suit.
    Last edited by Astro Spectra; Dec 17, 2012 at 06:44 PM.

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    Working:

    TD ---> RD
    RD ---> TD
    RTS ---> CD
    CTS (jumpered to RTS on side 1)
    GND ---> GND
    CD ---> RTS (RTS pin jumpered to CTS on side 2)
    RCLK ---> RCLK
    TCLK ---> TCLK

  25. #25
    ev351 No Longer Registered

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    I have managed to get my hands on a pair of simrex SNRDS serial 900mhz modems, so I think I will have a go with these: http://www.simrex.com/site/products/licensed.htm

    They do syncronous serial, so hopefully, should do the trick.