Issues with RFD868x-EU Telemetry

I’m part of a team of university students that realizes fixed wing drones with autonomous flight capabilities, in order to participate in an international universities competition I’m here to ask if anyone have ever experienced the same issue.

First of all I have the RFD868x-EU version with stock antennas, and I use the Mavlink protocol for the telemetry data and commands for the autopilot. The size of the message that must be transmitted should be 264 byte every iteration of the model that is 0.02 seconds, so 105.6kbps.

The main issue is apparently due to the limitation of the Low Power mode for EU modems.

In practice when we have LoPEU set on the Firmware using the RFD900Tools we can use duty cycle at 100%, but the power is limited to 5mW if I’m correct, with this parameters the telemetry visualized in QGroundControl is fast and fluid and everything seems fine, the issue is that the range is really short, we lose connection after only less than 100m in flight, so it’s completely useless for our use (we must have a range of at least 800m-1.5Km).

So we tried to set the modem in HiPEU, we have the duty cycle at 10% and the TX power to maximum, the range increase in this case but the biggest issue is that the telemetry is very slow and laggy, and it’s visualized in QGroundControl (or Mission Planner) at about 1Hz or less.

In both cases, all the rest of the parameters are set to defaults, and Mavlink option is enabled, we tried to change some, like airspeed etc but apparently nothing changed.

So the question is, is there a way to use this version of the modem for our case scenario?

I think we would not have issues with the unlocked modem (non EU).

If so, we would want to obtain good range and decent transmission speed as well, could you please suggest me some parameters we can set, can we use HiPEU, or we should use them in LoPEU and for example but with different antennas and play with some params of the firmware?

Consider that we also use some standard Holybro Sik Radio, that have a power of 500mW, and since we can use 100% duty cycle we have none of this issue, the only issue is that we obtain a range of 700m with them, and we thought the RFD868x-Eu could do better with almost the same settings, we would want to use the RFD but we can’t at the moment so any help would be very appreciated.

I had the same problems with 868 version. Tried different parameters, but it was still too slow. The RFD900 works a lot better. Don’t know much about the max range yet tho.

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