What’s a 3DR radio ?
3DR radio is a product from 3D Robotics which provides a telemetry link, and is often used by APM users. It is sometimes sold as a combo with APM.
The main differences between 3DR radios and Ultimate LRS are the following :
Ultimate LRS is much faster, here’s a comparison of connection speed between Ultimate LRS and 3DR radio :
3DR radio : 100 milliwatts
ULRS : 400mW, can easily be modified to 1 Watt.
3DR radio : $100 for two modules.
ULRS costs $57.90 for two modules (OrangeRX 1W)
It’s also possible to use a 1W module + a 100 mW module for a cost of $48.94
3DR radios : only a telemetry link, RC must be transmitted by another mean.
ULRS transmits telemetry linke and RC signals.
RSSI is an indicator of signal strength : it allows to know when we are at edge of reception.
ULRS provide RSSI on the TX and on the RX, which can for example be shown on an analog meter, a voltmeter, or an OSD.
ULRS provides an acoustic signal when a packet is lost, which gives a real time feedback of the link quality (for long range).
3DR radios have built in USB connectivity, while ULRS requires an FTDI (USB to serial) adapter.
3DR radios has a sensitivity of -117 dBm.
ULRS has a better sensitivity of -120 dBm.
The power difference of 10 dBm (1000mW = 30dBm) – (100mW = 20 dBm), and the sensitivity difference of 3 dBm (-120 dBm – (-117 dBm)), makes a total difference of 13 dBm, which gives ULRS a range of more than 4 times the range of the 3DR radios.
Good antennas allow to go even further : a user reached 40 km with Ultimate LRS.