Few days ago I mentioned that I'm working on my own DIY long range radio system (LRS) that I named QuadMeUp Crossbow LRS. Today I will share some more details about it.

First of all, I'm not creating anything new or "amazing". There are plenty of "DIY" or OpenSource LRS systems. OpenLRS for example. Or QCZEK LRS that is made from almost nothing at all. And amazing commercial systems like TBS Crossfire.

Is there a place for something else? I think there is. For example, I was so pissed of by complexity of OpenLRS. So many options, so hard to understand. Or do you know how much micro RX for Crossfire costs? And that you do not need 2W of power to fly up to 5km? And most of pilots owning Crossfire never flied > 2km?

This is why, my idea for DIY LRS is:

  • You can build TX and RX module without superb soldering skills or ordering PCBs from somewhere. All you will have to do is to order generally available development boards, maybe universal drilled PCB, buzzer and some cables. That is all
  • No fancy GUI. Hell, no GUI in the beginning at all. All options will be configured during flashing with Arduino!
  • 868MHz, 815MHz and 433MHz versions. Whatever suits you!
  • LoRa modulation and low power output. You can do amazing distances at 50mW and LoRa modulation
  • Practical range up to 5km. More than 2.4GHz systems, less than full scale systems
  • 10 channels will be fully enough, no need to send more and increase delays
  • 20Hz update rate in standard mode and 10Hz in long range mode (above 5km)
  • telemetry downlink
  • $15 for a RX module and slightly more for TX, but still < $25 for it
  • First versions based on LoRa32u4 II 868MHz LoRa boards. In a future maybe more powerful LoRa32 ESP32 boards
  • RF link will be handled by Semtech SX1276 or compatible RF chipset. Probably in a form of HopeRF RFM95W and Shenzhen HPD Technology's HPD13

Current state of the project

Current state? I'm almost ready to take it into the air. Both RX and TX software is almost ready for MVP. Real telemetry downlink is still missing, but that's a detail. For a few days I'm fighting with over the air performance, link stability and safety (so that Failsafe works in a reliable way).

One RX is already attached to my airplane and awaits for the weather for first flight. In the beginning only to record some data, test interference, failsafe and so on. During first flights RC link will be handled by FrSky X8R.

Crossbow LRS RX module prototype

Final version of TX module will not have OLED display. This is only for testing.

Crossbow LRS TX module prototype

Ah, by the way, Konstantin also known as DigitalEntity, creator of INAV is also working on his own LRS... Coincidence? I do not thing so :)