Portable DMR Single Frequency Repeater
I recently wrapped up a project for a customer which I wanted to share with you on the blog. The customer requested a portable repeater which could be deployed quickly in regions with no infrastructure, charged via solar, and be resistant to inclement weather.
The design was a delicate balance of size, weight, and power. The platform was designed and built to accommodate a Pelican Storm iM2075 form factor.
Solar Charging input is provided by a Neutrik Powercon connector, which was selected for its superior weather resistance. A custom cable accompanies the repeater to match the customer’s solar power connector. The unit utilizes a boost solar charge controller which enables it to accept a wide range of input voltages from various panels on the market and effectively provide charging voltage with low voltage inputs.
The integrated Protection Circuit Module of the battery protects the system from over discharge and other forms of abuse. Should the system be overheated by direct sunlight, it can simply be disconnected from power by the button on the panel shelf and then turned back on to restart the system.
The battery monitor enables the user to accurately monitor the charging or discharging state of the battery.
It automatically sleeps after 10 seconds to conserve power.
The repeater is based on the Maxon MDM-4000 mobile radio. It is available in either the VHF or UHF range and provides the Single Frequency Repeater (SFR) capability. This enabled the small form factor and more efficient power consumption of the build, without having to rely on separate RX/TX radios and a repeater controller. The SFR mode is a two-slot TDMA design that works by receiving on one timeslot and forwarding voice traffic to the second timeslot. This is best employed in conjunction with Hytera handhelds, which are capable of listening to both timeslots simultaneously utilizing Hytera’s Pseudo-Trunking technology.
Specifications
Size: 11.8 × 9.8 × 7.7"
Weight: 13lbs 1.8oz
Battery Voltage: 14.2V (12V Nominal)
Battery Capacity: 20Ah LiFEPo4
Rated Panel (Input) Current: 8A
Input Voltage Range: 0-60V
Max Recommended Panel Power: 105W
Frequency Range: 136-174Mhz
TX Output Power (Max): 50W
Temperature Rating: 14°F to 140°F (-10°C to 60°C)
Power Consumption
12A - 50W Max TX Power Output
8A - 25W TX Power Output
800mA - RX @ Max Audio
300mA - Standby
Inputs/Outputs
BNC Antenna Port
12VDC Charging
Neutrik Powercon (Solar Input) *Adapter Required