Repeater DR3000: When a network needs its own tower
There is a limit beyond which “just buy a two-way radio more powerful” ceases to work: the site is built up, the relief closes direct visibility, and people travel for tens of kilometers. This is when the network is completed by repeater and Motorola DR3000 It's a workhorse of this class. We understand when he is needed, what is required for him and what to expect from him.
When communications are lacking without a tower
The handheld station in the field can be heard for several kilometers, the vehicle-mounted with a good antenna - further, but it rests on the horizon and obstacles. Typical symptoms: at the edge of the territory, the voice breaks, in the lowlands and behind metal structures, the connection disappears, and an increase in the transmitter power does not help - it is not the weakness of the signal that prevents it, but the lack of line of sight. If humans and machines are constantly operating in such conditions, repeater pays off faster than any amplifiers and amplified antennas.
What the DR3000 can do
DR3000 – repeater standard MOTOTRBO: operates in the range VHF 136-174 MHz, leads 16 channels and receives a signal from subscriber stations, immediately transmitting it further from a high point. The main thing is three modes of operation: pure DMR numeral, classic analog and mixed mode, in which digital and analog subscribers coexist on the same network. In digital mode, one pair of frequencies carries two simultaneous conversations – TDMA technology divides the channel into two time slots. For the sprawling network, IP Site Connect (several repeaters combined via an IP network) and Capacity Plus (trunking on one site) are provided. The case is a standard 19-inch rack with a height of 3U, weighing about 14 kg, power supply unit 100-240 In built-in: it is placed in a server rack or in a cabinet at the facility.
Antenna and place decide more than power
The range of the repeater is determined not by the passport, but by the height of the antenna suspension and the relief: the antenna raised on the mast “sees” where no handheld station can see. Therefore, first choose the installation point and height, then consider the coverage area, and only then buy equipment. Important: the antenna, feeder, thunder discharger and duplexer are not included in the repeater supply - this is a separate set that is selected for the object. Reception and transmission are combined through a duplexer on one antenna; without it, two spaced antennas will be required.
Frequency and resolution – without it we will not start
The repeater needs a pair of frequencies: one for reception, the other for transmission, with the mandatory spacing between them. Frequencies should be allowed to use – this issue is decided before the purchase, not after, because the set of available pairs depends on the region and already occupied networks. If there is no permission, the correct way is to contact the regulatory authority or use the permitted range with respect to power: we will tell you how to arrange frequency support for your task.
A couple of practical points that are easy to miss. First, frequency coordination takes time, so the application for permission is submitted in parallel with the selection of equipment, not after it is received. The second: in a mixed park, where other people's networks work nearby, it is worth putting filtering and proper wiring of the antenna path in the kit - this is cheaper than then dealing with mutual interference at the working facility.
Who works on the DR3000 network
Ideal Digital Subscribers for the DR3000 – MOTOTRBO Family Stations: Vehicle-mounted DM4401 and DM2600 In digital, both data transfer and all network functions are received. Legendary analogue GM340 The handheld GP340 over the DR3000 also works, but only in analog or mixed mode – it is a convenient bridge for the transition period while the fleet is updated. It is important not to confuse standards: TETRA terminals, such as the MTM5200 and MTP6550, with the DR3000 are incompatible.
Where to start?
Describe the task: where will stand the dot, what height of the mast is available, how many people and cars are on the network, whether you need a connection between several sites. According to these introductory estimates of the coverage area, set (repeater, duplexer, antenna, feeder, lightning protection, subscriber stations) and availability in the warehouse - everything is specified by e-mail, the equipment is considered to be under the object, not from the shelf.
