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Problems with FRSky Module and or receiver

bogner

Junior Member
#1
Yesterday I lost my second tricopter to this radio setup. I was in a hover about 5 feet off the ground right in front of me and the tricopter just slowly started to climb. I couldn't stop it. I flicked my transmitter off and on after it gained 30 ft or so and it started to fall. I raised the throttle and it started to shoot off to the side and up and again wouldn't let me control it. I had to shut the transmitter off and on again and finally got the motors to almost shut off. It wound up crashing into the ground from about 50 feet up. Thankfully I didn't have my camera gear on it. This happened before but I wasn't sure exactly what was happening the first time because it happened so fast. This time it took about 30 seconds from losing control until the crash so I know it was a transmitter/receiver issue.

I am using a Futaba T9CAP with an FRSky DFT RF module. I cant remember the FRSky receiver I am using and I lost the top to it in the crash. It is a 9 channel receiver that has two whip antennas coming out of it. The second crash happened after only about 5 minutes of flying. I started with a fully charged 3S battery and the transmitter battery still had over 12volts.
It couldn't have been a range issue because It started less than 15 feet from me. Everything else on the tricopter is pretty standard. KK2 board RCtimer ESC's and motors. I had 5 of the 9 channels in use. 4 standard flight functions and one auto pilot. Is this a recurring problem with FRsky? I couldn't find posts about it. If FRSky isn't reliable any recommendations on a different module system that has solid reliability. Thanks in advance for any feedback.
 

bogner

Junior Member
#3
I have a couple of FRsky receivers but I just checked the first one I crashed and I used the same receiver on the second one. So the same receiver was on both. I had probably 4 or 5 dozen flights on the second tricopter before the glitch with the receiver.
 

xuzme720

Dedicated foam bender
Mentor
#4
This is the first Frsky glitch I've ever heard of. I've never had an issue with mine. I am using the JR type module though in the 9X but that shouldn't matter, the protocol is the same. I'm leaning towards crash damaged Rx as well. I've my share of 72mHz Rx's that "seemed" good, let me down in a model.
 
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Tritium

Amateur Extra Class K5TWM
#5
I read of a problem last night somewhere (RC Groups possibly). The user had modified his Futaba and the FrSky kit to be switched in and out. The popular consensus was that the issue was the installation rather than the FrSky parts. I am not saying this is applicable to the OP though! ;)

Thurmond
 

bogner

Junior Member
#6
Been flying rc for years and haven't had my old 72 MHz let me down too much. Yes the receiver I used in the second tricopter was from the crash of the first. I had the same issue when the first one crashed and the receiver was brand new when I installed it in that tricopter. I read something awhile back in another forum about the ppm signal used for FRSky was not done properly where if you were using more than 6 channels you could have an problem. I don't remember exactly. Something about the CPPM signal not being long enough to allow the signal to transmit fully. I don't know if this can affect something that is only using 5 channels though.
 

xuzme720

Dedicated foam bender
Mentor
#9
This might just be a case of bad component, namely Rx. Electronics aren't infallible and we've all seen out share of failures. I would take a few of your Rx's and do some range checking (not in the air!) on both the uncrashed ones and the crashed one and see if you can isolate the issue. It might be some local interference creating a dead zone for you or possibly just a bad Rx.

Also check the modules antenna connection, I believe that is also a weak point with most systems...
 

bogner

Junior Member
#10
No Doubt it could be just a bad receiver. The problem with range checks is that it is intermittent . I got well over 50 flights on it after setting up the second tricopter until it showed up. Thats the problem . You can range test once , or twice and say your ok to go but when it takes 50 flights to rear its ugly head how do you prepare for that. It defiantly was not a local interference because when it happened the second time it was right in front of me just over 10 feet away. I am reluctant to get one of these up and flying again and stick on a different FRSky receiver and have the same thing happen in a few weeks. I figured I would just ask and see if someone out there that knows a whole lot more than me would read this post and have some words of wisdom. Thanks guys.
 

xuzme720

Dedicated foam bender
Mentor
#11
I was only suggesting the range checks to make sure it wasn't an interference issue but you are correct about an intermittent problem, they are definitely the hardest to track down! I know being close would seem to rule out interference but that is not always the case, although if it was in your case, something strong enough to cause it from that distance would likely show up much more often. So it still looks like a gremlin in the Rx...The only problem with that is it's passive and would need some very specialized equipment to check the components. Maybe use that Rx in a foamy or plane where you can set the fail-safe and would be more forgiving if the problem comes back? Just trying to help...
 

bogner

Junior Member
#12
I have found a couple of threads on other forums referring to FRSky problem with the PPM code. It is set up at 18ms and to properly transmit all the information and start again a ppm signal should be 20ms. I have read there is a firmware fix that sets the FRSky to 27ms and that fixes the issue. The problems I have read about are freezing and locking. Most of these threads are a year or older. Does anyone here know about this and what it is all about. To upgrade the firmware for the receivers you need a special patch cable so want to make sure this is the way to go. Just google FRSky CPPM problem and there are a few different ones.
 

Tritium

Amateur Extra Class K5TWM
#13
Like Bruce (RC Model Reviews) said of his HK FrSky Tarannis that lasted a few minutes before dying then suddenly came back to life later: He could never trust it to fly with an intermittent issue. Just put up the suspect receiver and see if the problem ever happens again with a different receiver. If so then FrSky Module or Futaba is the issue.

Thurmond
 

vk2dxn

Senior Member
#14
Tell you a quick not so funny story about local interference (long ago when I was a meanie).
Back when I used to operate 27mhz cb a lot a few of the local kids had cheap plastic rc's that was centered on 27.145mhz, the am call channel is on 27.085mhz and the rc transmitters would overload the front end of my radio to the point where I could not hear the person I was talking to so I used to tune up onto 27.145 and lock the ptt with only 4w mean (average) power output and it would literally stop the little rc in its tracks. The rc transmitters are really low power and the new 2.4ghz transmitters are even lower power. There is a lot of rf traffic on 2.4ghz from high power microwave ovens to relatively low power wifi node's and even 2.4ghz ham band. I don't know how good the filtering is in the front end of the frsky receivers but if it is poor even an average power adjacent signal could be enough to make it play up.
I would suggest trying a different receiver and give it another shot
 

bogner

Junior Member
#15
I have two other receivers on quads right now that have been doing ok but I don't fly the quads as much. I will keep going with those two and if it doesn't happen again great . If it does I will let you all know.