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Interference at 2,4GHz in McCoy flying field
#1

Because of the incident last December that I almost crashed my Freya helicopter, I endeavoured to do a bit of analysis on what is happening on the 2.4GHz band. I don’t claim that this is accurate but this is how I see the problem arises.

First, I used the spectrum analyser of the TS16S radio to capture the 2.4GHz spectrum. Here’s what I found. There are instances where I got some readings with frequency spikes along the spectrum. Unlike the old days wherein each radio is operating on a fixed frequency, now a days, radios are hopping within the 2.4GHz band looking for a clean signal and will use that signal for a while before hopping to the next signal. The algorithm implemented by the manufacturer are complex but for illustration purpose, say the radio has picked 2.400GHz. So radio is communicating with the transmitter at 2.400GHz. Then before it hops to the next available frequency a strong interference comes in as shown in the spectrum analyser. During this time, you will loose connection until the radio decide to hop to the next available frequency. When it happen, the receiver will go to failsafe settings (usually set to No Pulses). Which means all control signal will go at center stick and throttle at zero. And this is where the OH SHIT moment happens.

   

Here's the actual log when the incident happen. It shows that the throttle went to failsafe but when the radio hops to the next frequency, I was able to gain control to execute autorotation. But for helicopter, when the throttle drops to zero, it will take time to spool the rotor. Before it can generate lift, the heli is already on the ground. The only way out is to AUTOROTATE and land the heli. For plane, it is less forgiving as it will still glide during that short period of time. But check your ESC settings because there are ESC's that once the throttle is lost, you have to go to ZERO throttle before you gain throttle control. No matter how you push the throttle if you did not pull it down to zero, you will never gain power.

   

Maybe its time to run at 900MHz. Crossfire or FrSky R9M module. I like the R9M module cause FrSky has a receiver for this module that supports FPort (Control signal and telemetry signal in one wire). FPort is SBUS plus SPort in a single wire.
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