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Thread: Quantar simulcasting question/setup

  1. #1
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    Default Quantar simulcasting question/setup

    Hey everyone,

    Ok so what hardware is required to get conventional p25 simulcast working?

    I have 2 quantars setup and working with an ATAC3k in conventional p25 repeat. Works great!

    radio keys in site A area and radio in site B area hears it and vise-versa and both can talk/hear the DIU.

    I have GPS 10mhz and 1PPS refs connected to all the hardware and options set and i set the ATAC and Quantars to simulcast and i get nada. I've played with the launch time but no luck.
    Both quantars have been set to the same TX/RX freq and there is a 30% overlap in coverage area.

    We want to simulcast so we don't have to change channels when we hit the boundary from one area to the other area. 1 channel to rule them all.

    Any thought are greatly appreciated!

    Thanks
    J


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    P25 only?

    At the ATAC3k; 1PPS into the comparator
    Comparator set to Conventional / Standard / Simulcast Enabled
    Trying setting the launch delay to 200 for now. (you can dial it down once you calc the link delays)
    Under conventional system make sure both default transmitter steering and HDLC addresses are 3F (hex)

    For the quantars;
    10Mhz and 1PPS to each Quantar
    Quantar V.24 to the ATAC3k
    Quantars are set to simulcast
    Each device has their own unique site ID
    Configured as base, not repeater

    In the comparator you should look at the status panel to make sure the links are there (to all devices)
    In the comparator, you can look at the status report screen to see what errors exist while trying to transmit, etc.

    (there is an assumption you don't have v.24 linking issues since you already have a cross site connection)

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    All of the above is correct.

    You also want to make sure both modulation compensation adjustments in the Quantars have been performed and are set as well as you can get them. There really isn't any "phasing" to P25 simulcast like there is with analog.

    Use the tools in the comparator to measure and set your link delays.

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    When you say "simulcast is nada", do you mean that only one TX comes up at a time or that you have distortion in the overlap?

    Sent from my SM-T350 using Tapatalk

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    Simulcast was nada. Only one TX came up, but with the help of Phantom and d119 both sites are working now, kind of.[Thanks for the help!]
    The 2 site are connected via IP STUN over IPSec VPN so we are dealing distortion and TX sync timing due to IP network latency issues but i think we can work past that with some adjustments and fine tuning. We are slowly adjusting the launch time and working on reducing the network latency.

    On a side note: I got a Quantar VHF R1 receiver im looking to trade for an R2 if anyone has a lead.

    Thanks again everyone for the help!
    J

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    Since you mention IPsec VPN, I am guessing that youíre running this over the public internet?

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    Yep
    But i think we might ditch that and move to a radio shot. I'm in Alaska and T1's circuits cost an arm and both legs here and nobody sells fractional T's here and the sites sit in different telcos serving areas.
    Capture.JPG

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    You wonít get an ATAC 3000 to work in simulcast via public internet. You need fixed latency with no jitter as thatís what the synchronous V.24 links that the ATAC was design around can provide for you.

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    How far apart are those sites?

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    30.91 Miles apart.
    Anchorage Site is 199 Feet high building and 85 Feet ASL - 61-13-09.0 N, 149-53-30.5 W
    Wasilla Site is 125 Feet high tower and 459 Feet ASL - 61-36-46.5 N, 149-27-03.8 W

    We got a new pair of Ubiquiti AF5U radios that are good for 60 Miles(more like 45) that we are contemplating using.

    Thoughts?

    Thanks
    J

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    Anything that gives you something resembling fixed latency will work with the ATAC.

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    Quote Originally Posted by syscon411 View Post
    30.91 Miles apart.
    Anchorage Site is 199 Feet high building and 85 Feet ASL - 61-13-09.0 N, 149-53-30.5 W
    Wasilla Site is 125 Feet high tower and 459 Feet ASL - 61-36-46.5 N, 149-27-03.8 W

    We got a new pair of Ubiquiti AF5U radios that are good for 60 Miles(more like 45) that we are contemplating using.

    Thoughts?

    Thanks
    J
    The simulcast delay spread is going to create time differential interference TDI, problems unless there is some significant terrain barrier in between. Radios used in aircraft, or otherwise able to receive both transmitters are going to be affected.

    Sent from my SM-T350 using Tapatalk

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    I have apparently frightened the OP off the topic. There are several solutions.

    1) linear simulcast to improve the situation. But this is not going to help significantly in the overlap zone, it will only minimize it.

    2) directional antennas, but these will remove the overlap coverage.

    3) multicast on different talk out frequencies. This will allow reception in the overlap and if the radios are set to scan, this will make the coverage seamless. You also will not have to be concerned with jitter and packet loss.

    #3 might be your friend.

    Sent from my SM-T350 using Tapatalk

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    Quote Originally Posted by RFI-EMI-GUY View Post
    1) linear simulcast to improve the situation. But this is not going to help significantly in the overlap zone, it will only minimize it.

    Hmmm, how does one achieve LSM on a Quantar?

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    Quote Originally Posted by MattSR View Post
    Hmmm, how does one achieve LSM on a Quantar?
    With that site seperation it won't buy much anyway.

    Sent from my SM-T350 using Tapatalk

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    Quote Originally Posted by MattSR View Post
    Hmmm, how does one achieve LSM on a Quantar?
    Assuming you are running an already functioning simulcast set-up; in the Quantar RSS > RF Configuration change ASTRO Tx Filter to Narrow Pulse.
    Wide = C4FM
    Narrow = CQPSK (LSM)

    Max Site Separation:
    Wide = 8 Miles (at 12.5khz)
    Narrow = 15 Miles-ish (at 12.5Khz) (13-20 depending on engineering factors)

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