RX connection Dropping

I am having an issue and am not sure why it is happening.

I switch flightcontrollers from librepilot revolution to the pixhawk. I also have the 915mhz telemtry radio other those 2 things everything on my quad is the same. I am running a frsky xjt moduel and x6r rx. Never had an issue with dropping connection with the revolution FC.

It never happened in flight so far but i only have a couple tuning flights. On the pixhawk so far. There have been a few times where the transmitter wouldnt connect to the rx i would move the transmitter around and it would finally link up.

Well i was just outside auto tuning the pitch axis and everything was going well i went to correct some drift and no response. I didnt even get a voice alert telling me that signal was lost. I was 10ft from my quad. It ended up crashing into my neighbors house broke 2 props and knocked my gps puck off the mast. Thank god nothing else broke. I have over 1k in this thing and that would have sucked.

So my question is obvious why am i losing my link to my rx with the pixhawk? I didnt set up failsafes yet because i am not flying more than 20 feet from myself, like i said i am tuning and testing. Didnt think i would need them quite yet. Rx is powered from pixhawk. Pixhawk is powered from power module. Any ideas on this?

Well just found out that crash killed one of my motors…just wonderful! Not sure why i am having random RX issues with the pixhawk…sucks though. looks like quad is grounded until I can afford new motors!

Can you please post a log file from the Pixhawk.

Off hand there could be multiple reasons why this happened but until we can look at the log it would all be guess work.

BIN File
LOG file

I kind of had it happen again while trying to setup a failsafe after it all happened. I say kind of because the quad wasnt flying. I was checking failsafe activity and turned off my transmitter which activated the failsafe. When I turned it back on they wouldnt connect. I had to turn off radio again and then turn is back on.

This doesn’t sound like a flight controller problem but a connection problem with the radio. I use those same modules except I have an X8R and have no issues. I will say that the XJT module plugs into the back of the radio and those pins are not vary secure. It maybe that the module is a little lose on some of the pins causing it to not startup or disconnect.

You should probably check the LED on the XJT module and maybe move it around a little and see if this is where your problem is.


Your receiver input flatlines at about 63000, just after your 3rd pitch correction in autotune.
as @iseries said, it doesn’t look like an FC problem but a radio problem.

I am curious as to why you were giving it yaw correction as well as pitch correction during auto tune though?
CH4 almost matches the input of CH2?

I was having issue with it yawing on its own. I assumed it was a tuning issue. The autotune of the yaw axis was next after the pitch axis. There was a light wind yesterday so I was trying to keep the copter oriented correctly. I hope that answers your question.

I contacted getfpv.com. Thats where i got the module from. We will see what they say. I have not experience these issue with my little 250 size quad yet. Which is why i figured it had to be something with the pixhawk although i wasnt sure what is could be. I might make a quick post on the openrc forums as well about it. I am using a 9xr pro.

The issue is random and rarely happens.I never had the issue with my DJT module. So I guess that narrows it down to the module itself…

On a side note I have new motors coming for my quad since I had one of my old ones fail.
I got 4114 330KV motors on the way. I am going to lengthen the arms and run 15" props on the thing. Should fly nice

The fit of the XJT module in the back of the Turnigy 9XR radio is not a tight fit. I laid tape over the module to ensure it cannot move around.

Do set up the radio failure failsafe (RTL) asap!