If you already have a Motorola Quantar repeater on P25, joining our network is easy. You just need to obtain a few more items:
Of course, you'll also need an internet connection of some kind. Current systems are using everything from DSL modems to cellular connections to 100 Megabit pipes! See the technical info section for more information about how to connect to the system. When you're ready, contact us for the information you'll need for your router.
If you have some other kind of P25 repeater, contact us and we'll see if it's possible to connect it to the system.
If your local P25 repeater is already on our network, using it is easy! Version 1 supports only one talkgroup: worldwide on 10100.
UPDATED Version 2 Talkgroup list:
Under each of these groups are three "tactical" channels. These are:
For example, if you are in New Zealand and want to speak to a US station on the worldwide net, you could use 10101, 10102, or 10103. If you are in Austrialia and want to speak to another Austraila repeater, or even Hawaii, you would use 10401, 10402, or 10403. By doing this, you keep traffic in your part of the world.
10100 will be the default talkgroup for many repeaters, but this will be a local option. To use another talkgroup, just key up on that talkgroup and release, You will be connected to that group and hear a voice announcement. When you're done, just key up again on the main group for your repeater, or let it time out and it will revert. The time out is also set by local option but 1 minute is reccomended.
If you're using our network, program your radio ID with your CCS7 number. You can get the number from Here. Just pick CCS7 as your radio type. (even though it's issued by DMR-MARC, we're using this on P25NX for consistency.)
There are many different radios that are P25 compatible. Most of the users find that the Motorola brand offers the most utility and bang for the buck. There are portable and mobile radios available, and they range in price from about $150 USD up to well over $5000 ! Several options are shown here.
The XTL5000 is a high-end radio. It was mostly used by public safety fleets. There are many options for this radio, including "dash" mount, remote mount, and hand held control head. These come in VHF and UHF bands, in both 45 Watt and 110 Watt versions.
The Astro Spectra is a high-end radio. It was mostly used by public safety fleets. There are many options for this radio, including "dash" mount, remote mount, and hand held control head. These come in VHF and UHF bands, in both 45 Watt and 110 Watt versions.
This is based on the "Astro Spectra" one-chip V.24 design. We have made these available for repeater owners to use instead of the hard-to-locate Motorola V.24 daughtercard for the wireline interface. These come with a 29" cable and db-25 connector, ready to plug into a Cisco router.
At each site is a Quantar repeater. The repeater must have a V.24 interface, either through a Motorola TTN4010 card, or a P25NX V.24 interface board. The V.24 interface is then connected to a RS232 Cisco DCE cable to a WIC-1T card in a Cisco router. The router is typically a 2600XM series, or an 1841. The Quantar provides serial synchronous data in HDLC format. The router can take this data on the serial port, and convert it to TCP/IP data. In this system, the Cisco Serial Tunneling (STUN) protocol is used for the conversion. This is a very lightweight protocol that adds just a few bytes to the beginning of each data packet with a STUN ID, and a count of bytes to follow.
Version 1 of the system uses a central server as a reflector. The STUN destination in each site router points to the central server, and the server accepts the connections. The server makes each Quantar think it’s connected to one single other Quantar. (RT/RT mode). The central server takes the data stream from a receiving Quantar, and reflects it out to all the other connected sites. Some information is pulled from the data stream such as talk group ID, site ID, and radio ID for display on the system website. Code in the central server also handles special cases such as DIU-3000 connections, and Astro-Tac Comparators. Transmission end is also detected in the code as the turn-off message from field units is not a reliable method.
Once the basic V.24 and router setup is done, the system operator needs only the STUN ID assigned to the site, and the server IP address. Once those are configured the Quantar makes the connection and network access is granted.
Version 1 supports only one talk group (TG) – worldwide, on TG 10100. TG1 is not carried over the network, but local users on TG1 do interfere with users on the system trying to communicate on TG10100
Version 2 is shown in figure 2. This version uses a completely different topology and method for network communications
V2 still uses the Cisco setup as shown in V1, but also has an additional piece of equipment. A Raspberry PI (Or Beagle Board Black), which is connected to the 2nd Ethernet port on the Cisco router. We will use a Pi for the purposes of this discussion. The Pi is used as a protocol converter, as explained below.
V2 uses several network technologies. The first is Dynamic Multipoint Virtual Private Network (DMVPN). DMVPN allows a private network to be built between routers on the internet. With this, each site gets a virtual static IP assignment. DMVPN works behind firewalls with no need to open ports for user sites, and has features that allow for both scalability and redundancy. It does require a more complex setup in each router however, but a template file is available to simplify this for site owners. The second new technology used in V2 is IP multicast. Multicast is a method of sending data to only those locations that subscribe to it. This limits network traffic and load on the systems. No central server is required, although centralized routers are used to manage the subscriber tables and direct the traffic. In V2, every talk group gets a dynamically assigned multicast address. For instance, TG 10100 is multicast address 184.108.40.206. The Pi at each site handles converting of the TG ID to a multicast address, and the registering and dropping of that sites’ interest in that talk group/address. If a user wants to change talk groups, they simply key up on the selected TG, and the pi will de-register from the current group, and register with the new group. Traffic destined only for the new group will be sent to that site. This eliminates interference between talk groups, and lets the network handle the routing. The Pi also converts the TCP/IP STUN data to UDP multicast data, and vice-versa. With this setup, intra-regional communications never leaves the region. For example, a conversation between Australia and New Zealand never goes further than the hub in Hawaii. Private hubs are also possible, but discouraged. The same thing can be accomplished with a new talk group, and still take advantage of the system’s redundancy.
Once the basic V.24 and router setup is done, the system operator needs several IP addresses assigned to the site, and the hub router IP address. In addition, the Raspberry Pi needs to be setup and the software installed. A config template for the router will be made available as soon as possible, and the IP addresses provided to system operators. For the Pi, the plan is to use a modified “Crompton Allstar” image, with all of the necessary software installed and mostly configured. This will be made available as a download from the P25NX site for site owners to burn to a microSD card. The config files will not be published for security purposes, but will be made available to system operators. Once the network and Pi are configured, the Quantar makes the STUN connection to the Pi, and the router makes the VPN connections to the rest of the network.
Not known at this time. In theory, it is expandable to no limit of TGs and hubs, although the setup becomes more complicated for each hub. It is currently planned to have 2 hub routers for each region (North America, Pacific, Europe) If one hub router goes offline, the other hub router for the region takes over.
The P25NX system is intended for Amateur Radio use only. You agree not to utilize the P25NX system or any components purchased from this site in any public safety application. This does not preclude normallly accepted amateur radio support for emergency operations. P25NX and it's operators shall in no event be liable for any direct, indirect, punitive, incidental, or special consequential damages to property or life whatsoever arising out of, or connected with, the use of the P25NX system or products purchased from this site.
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