FM30 mavlink range, looking for advice
After testing the FM30 with the regular FR receiver I think I will remove it from my gear of choice again if there is not something I have not yet considered. Should anyone have some advice I am all ears. Note that my focus is mavlink only: The maximum reliable distance possible to achieve. I do not care about the radios used for this test at all. For me they are backup only solution as a last resort should ardupilot fail terribly.
My first challenge is that I am focused on model boats. Receiver antenna usually never higher than max 15 cm above water level. And my tripod with gear is on the bankside, usually max 2 meters above water level: I have seen impressive distances achieved with SIYI with drones high up in the air. But honestly, if I could get mavlink reliable up to 1 km then I would be very happy indeed. Boat on water is a totally different ballgame.
Leading me onto the second challenge. These boats usually (mine always) are equipped with a wifi enabled echo sounder. Usually combined with either a wifi booster onboard, or with a router in boat combined with a router on shore. Typically, such sllutions can get the remote fish finder screen (app running on the tablet on shore) working stable up to 350-500 meters. Add in an ESP to a serial port and mavlink by UDP is also covered for (almost) the same distance.
Now: I had hoped the FM30 to be somewhat robust to this competing 2.4GHz usage as the FM30 is a LoRa solution. So I bought it with the FR receiver and installed for a test. I ended up using SBUS as config as I struggled to configure multi with siyi as choice on the two radios used for testing (radiomaster boxer and pocket respectively). I did not set any other parameter for the external radio module, but did deactivate the internal radio module on my transmitters. As for Radio setup in genersl I only configured sticks and switches so I could control boat and gear in the boat by the transmitter if I should ever need to.
During testing these radios stood upright, 2 meters above water level. Android Tablet on separate tripod some meters aside. Using the GCS app I activated GCS failsafe for ardupilot. Added a waypoint 1 km out in the water and set it as a guided target. And then watched during multiple tests with different radios and even with no radio at all (relying on the ESP), waiting for the failsafe to kick in.
I was very disappointed by the observations. The UDP connection over the ESP for comparison regularly got failsafe around 390 meters (397 max), which is satisfactory and as expected. But my FM30 that I expected to beat this hands down had the best test result on 342 meters only. Not by far what I expected. Note for comparison that I removed the previously built in Skydroid receiver (shipped with their T10) before this test. And in this exact same somewhat hostile 2.4 GHz environment the fish finder always caved in first, while the previously used T10 providing mavlink usually could keep on up until 600 meters.
Let me also add that I have a friend in another country testing a similar setup in parallel. He never uses RC radios. So he set up the FM30 in his “land station” (box with an on shore router for that fish finder). Turned the FM30 dial to UART. And performed range testing. His results were comparable to mine, he was just as disappointed as I.
Could there be some setting on my radio that I have overlooked on my radio transmitter when using the FM30? As it offers the same user friendly mavlink by Bluetooth option as Skydroid my hopes were high. This experience was very disappointing indeed. Being LoRa based I also would not have expected it to be beat by a T10 by such a margin.