Help! Continual suspected radio issues, troubleshooting

Andy.T.

Member
I've been having what feels to me at the controls like complete loss of control events. Several times in an FT P-40 (one being almost a crash, the others were more or less just brief blips), and lately every time I've flown my new FT Cub. I thought I had a pretty good theory and solution that I think I posted about not that long ago (first model OrangeRX that apparently was great at crashing planes), but it happened again with a brand new Lemon LM0080.
I just don't know what to suspect at this point, so any thoughts are welcome. Might be prudent to info dump on setup and situation. I'll go with most recent, as of last night's...event.
TX, DX6i. This one was a hand-me-down (mine's memory is full so for the Cub I switched to this spare) I had to fix the hinge on the plastic exterior for the antenna as it came to me floppy. I mention this because I don't know how likely or possible it is that the radio or antenna are bad.
RX, as mentioned brand new LM0080. Ailerons were set up on separate channels; needed 3" extensions on them.
Motor, FlashHobby 2836 1120kv, ZTW Beatles 60a ESC (I know that's overkill, I had just taken out a different 30a ESC that I didn't like how it made the motor behave and the 60a was just sitting on my bench ready to go so I had popped it in for this flight)
Servos, 4x 9g, MG90S
Field I was at is actually pretty big. It's a track, a handful of soccer fields, and a few conjoined parkinglots. Trees surrounding the whole area, with 40-50ft canopy. I was using the track, and over one of the parkinglots. All in all, I was making rectangular patterns with me in the middle, maybe 600ft x 300ft. There is a water tower that has cell tower repeaters on it, probably 700ft from where I was standing. I don't think I got any closer than 400ft to the tower.
I'm relatively confident something made me lose control as opposed to a stall. But if there's an argument for that, I'd love to learn.
No idea how likely/possible brownout is, but I hear people talk about it. To my understanding of what that is (drop in voltage to the receiver) I wouldn't think this plane, setup, and how I was flying it, would lead to a brownout.
Is not having a satellite a problem at these distances of up to 600ft away and hundred or two ft up?
What seemed...suspect to me, is both times my Cub was brought down by a loss of control, it was at an almost identical attitude towards me. That being, flying perpendicular to me, starting to turn towards me, with maybe 30deg of bank. This time, as I estimate w/ google maps, the plane was only about 250-300ft from me (~450ft away from the water tower).
Based on all this, if anyone cares to apply their own experience to hypothesize, I'd love more input than what I have on my own.
 

Tench745

Master member
Radio issues are probably one of the hardest to suss out remotely.
My first bit of advice is, remove as many variables as you can. Go to to the last known good setup then start adding the variables (components or situations) back in until you get a failure.
As an example: Do what you have to in order to use the old TX and range test it. If it works, fly with it. If you still get a failure it's not the TX's fault. And seeing whether that failure only happens in the air or not gives you additional diagnostic information.

To check for brownouts, if you have a watt meter, check what your power system draws at full throttle. Then see what happens at full throttle with of all the sticks at full deflection.
 

LitterBug

Troll Spammer
Sticks at full deflection is not enough. The sticks /servos need to keep moving for maximum draw. Keep moving the sticks to full deflections at the same time To create max load on the BEC.
 

Piotrsko

Master member
Hmmm cell towers..... 5g has transceivers at 2ghz, and they are high powered looking for any signal in that band to talk to. They don't speak airplane.

No mention of fences on the soccer fields, or other metallic things which will impede a 3" diameter signal stream with sinks and reflections.

First make sure your radio antennas all work and aren't wobbily wires. Second, go to your field with a friend and do a range check looking for erratic operation on the airplane with the transmitter antenna pointed away from the plane. If it passes the range check, then an orbit within the range check area should work with gradually expanding the orbit. Note that the transmitter antenna has to be a right angles and visible to the airplane antenna for maximum range. I suspect the cell towers to be fatal to happy flight, but you could be lucky.
 

Andy.T.

Member
d

I see you found the other post with similar problems.
I did. this problem has had me lose sleep and work productivity. I hate problems without answers and understanding. This obsessiveness is probably one of the things that makes me a nerd :)
 
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Andy.T.

Member
Hmmm cell towers..... 5g has transceivers at 2ghz, and they are high powered looking for any signal in that band to talk to. They don't speak airplane.

No mention of fences on the soccer fields, or other metallic things which will impede a 3" diameter signal stream with sinks and reflections.

First make sure your radio antennas all work and aren't wobbily wires. Second, go to your field with a friend and do a range check looking for erratic operation on the airplane with the transmitter antenna pointed away from the plane. If it passes the range check, then an orbit within the range check area should work with gradually expanding the orbit. Note that the transmitter antenna has to be a right angles and visible to the airplane antenna for maximum range. I suspect the cell towers to be fatal to happy flight, but you could be lucky.
LOL @ "they don't speak airplane"! Yeah, other than the trees on the outskirts of the fields, I had clear line of sight. Was flying a solid 2 mistakes up while I was trimming the plane again and just getting used to flying there.
I bet when I was setting up to practice some landing approaches, I had drifted closer to the water tower and cell repeaters (to get longer approach) than I had when I was just flying some patterns. The water tower was more or less in a line with me and the plane when I lost control. Do we have any suspicions or even better, know how far away those repeaters would be causing noteworthy interference? Are things like wifi networks ever an issue?

I think two procedural things I learned so far that I'll make sure I do more consciously, is the binding thing Bricks talked about in earlier thread (I've always just, stood at my workbench w/ my plane; never walked a dozen feet away and purposefully put my body between TX and RX), and make sure my TX antenna is bent at it's elbow. I'm not sure I've ever paid attention to that, and they probably are usually straight - so when I'm facing the plane the antenna is almost pointing at the plane, not presenting it's length to the plane. But, I will also double check the wires for floppiness.
 

Andy.T.

Member
Sticks at full deflection is not enough. The sticks /servos need to keep moving for maximum draw. Keep moving the sticks to full deflections at the same time To create max load on the BEC.
So, this isn't a big plane nor big servos. I am starting to think that the FT-suggested weights on these planes is a pipedream, though. My Simple Cub came out with an AUW of closer to 700, 750g - a lot like my P-40. Both of those, plans seemed to think somewhere in the mid or upper 400g range IIRC. Not flying it hard and fast (1/2 - 2/3 throttle w/ the orange 2836 1120kv) Full throttle, pretty sure this has been giving my P-40 up to maybe 45mph; the Cub feels a little slower to me), control surfaces are not oversized and just standard 9g MG servos.
How likely ARE brownouts? I am a little annoyed that finding and ESC with more than a 5v, 3a BEC seems to be nigh impossible. I would prefer to be way overkill on stuff like that that could bring a plane down. Maybe there's such a thing as an external BEC? That seems like it's probably overkill for a 1.5 lb foamy though.
 
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