Intermittant pulses from stick inputs

Having trouble with a frsky receiver Using a T8SG Plus (Now my favorite TX and all the spektrums sit on the shelf). I can bind the radio and see reactions to input in Betaflight but have never got it to arm (switch arming). For whatever reason my inputs all work, but in 30 ms intervals. The throttle goes between 885 and 1260 (when left low) and the other inputs stay stable at 1500 but only bounce when moved. The screenshot below is BF with the throttle left low and the aileron held full right.



The blue line at the bottom represents the throttle and the orange line bouncing from center to high is the aileron. If I center all sticks the lines (inputs) all stay centered correctly and the CH5 and CH6 switches stay where I put them (the green lines on the top)
This transmitter is fantastic on five other receivers, all DMSX, but this is my first attempt to bind it to frsky.

Need Help, going crazy trying to figure out what is happening!

Hello SteveB,

Looks like I have hit the same issue, "..can bind the radio and see reactions to input in Betaflight but have never got it to arm (switch arming) ..."

Still playing around the settings, and no clue how to fix it.

Just like to see if you had finally got it work, and possible to share your solution here.

Many thanks

Haven’t figured this out yet. Have now bound my T8SG to other FrSky rx’s with no problem but I have two receivers that do this. Still trying to figure out why.

What type of receiver has these symptoms? All the same? Any of that type that do work?
What is the receiver output format (pwm, ppm, sbus)? How many channels enabled in the model? Same issue with a freshly created model with default mixers?
Has the Freq-fine option been optimized with the problematic receivers?

hexfet wrote: What type of receiver has these symptoms? All the same? Any of that type that do work?

They have all been integrated (on FC). Two that did work were from Banggood; the one on KingKong 125 and one on an E010. The ones that did not work were from BetaFPV betafpv.com/products/f4-brushed-flight-controller-frsky-rx-osd and the “SharkWhoop” from Banggood that says Lemon FrSky on it.

What is the receiver output format (pwm, ppm, sbus)?

Sbus

How many channels enabled in the model?

Can’t remember but i think they both bound to the D8 mode with at least 6 channels enabled (4 + arm and mode switches) and more would be added if they worked.

Same issue with a freshly created model with default mixers?

Yes

Has the Freq-fine option been optimized with the problematic receivers?

No. Researched this a bit but a little out of my league.

With integrated receivers especially try the Freq-fine setting. Adjust positive and negative in steps of 10 until bind is lost, then set to a value in the middle. Is there a receiver LED that indicates bound? It might start flickering when close to losing bind.

That said, the symptom of channel values not being stable doesn't sound like a frequency mismatch.

No, I agree that it doesn’t seem to be an issue of poor reception. The results are very consistent and repeatable.

One thing I wondered about was the frequency hopping sequence; it’s as if the radio communicates, then goes to failsafe value, then repeats in quarter second intervals. However the receivers I have that work have identical hop list.

Answers to the questions,

I have two models , ELf Dys (stock frsky D8 ) and a BNF model with Queen SPR F3 receiver (I think it is)

They use SBUS, 8 channels. Binding works , all switches responsive showing in BF, no clue why the arming won't work.

I do not know if this is reception issue, I may go ahead to find the centre frequency as suggested. Thanks

I might figure out the fix with help from other forum.

The additonal setting required is to set the 'scale-' of THR to 125, in order to get it armed. I don't yet know the exact technical reason behind. Hope it helps

Give it a try, happy flying