ImRich
Veteran
Location: Derry, NH USA
My Posts This: Topic Forum | We all know that the lawyers are too active in the USA these days, so most companies are simply trying tol cover their assets. 
On the other hand, there are good engineering practices and guidlines. Yes, you can get away by pushing the limits, but often when you do, your safety margin is a lot smaller.
Not to get into such a debate here, I thought I'd just point out some backround facts that I found.
If you are personally comfortable with your low level receiver electronics being close to your high energy ignition system, then don't worry about this!
I have some experience with radios, electronics and computers (both software and hardware). Does this mean anything? NO!  But I do strive to keep all of my receiver electronics and any associated wiring as far from my ignition system as I can. There is all sorts of methods where an ignition system can interfere with a receiver. From electical impulse noise degrading your SNR (signal to noise ratio), to EMP (electro-magnetic pulse) creating surges or 'noise' indirectly or directly in your wiring or electronic components.
If you're flying and your happy then
But if you're trying to setup some new options, I'd take the conservative route and keep things as far from your ignition system as you can.
For those who might wonder how to be sure, I would reccomend that you perform what I call an 'extreme range test'.
The following works or both PCM and PPM systems (note, both are FM but many people refer to PPM systems as simply 'FM'). With PCM you have to pay close attention to notice the point where servo response is starting to slow down, or you lose control competely. It depends on how you have your 'fail safe' setting programed in the PCM receiver (do you have it set for 'hold' or for 'fail safe'). I have my throttle programmed to a 'fail safe' setting of IDLE, and all my other controls set to 'hold'. This way if I get interference, the engine will go to idle. But the other controls will hold the last good position. If you prefer for this test only, set your pitch to "fail safe" at a slightly negative pitch so the heli will stay on the ground if some interference happens.
Here are the steps:
1) With your engine OFF, set your heli on the ground. Either extend one section of your TX antenna or keep it collapsed (per your radio's manual). Start to walk off in one direction while watching your control surfaces. You want to move the control surfaces regularly and notice both how fast they respond and how smoothly they respond. Also notice if there is any jitter in any control surface.
2) Keep walking away while watching your control surfaces. You may need a helper to watch the heli as you may get too far from it to see the control surfaces. At the point where you start to some jitter in your control surface (for PPM/FM systems), place a mark on the ground. If you are using a PCM system, you need to watch for the servos to start acting slowly, or at complete loss of control. Again, mark this position on the ground. Then move a few steps closer to your model to see that the control comes back, then return to your mark to see that the control is consistantly lost or erratic at this point.
3) Now, return to your heli, and start the engine. This is the dangerous part!! Your heli is going to be running, and you may lose control so be quick to get closer to it if it starts to act erractic (or quickly extend your TX antenna)!!!!
4) Walk away from your heli with the engine running in the same direction as you did in step 1 until you find the point where you start to lose reliable control (or complete control). Then step a few steps closer to verify that control returns and then step back again to see if you found the range at which you lose control with the engine running. If you are very brave you should do this with the engine running and the blades at hovering or even your idle up 2 speed!! Of course, I don't know how you can safely do this with blades on the heli. I have heard of people using a head loading device instead of actual heli blades, but if you keep a slight amount of negative pitch, the heli should stay planted if you have a PCM system. I would hesitate to even attempt this with a PPM
Is the point in step 4 the same distance as in step 3?? If so then you are not experiencing any ignition interference. If it is very close to the same point, then you have some minor interference.
However if the point in step 4 is not very close to the point in step 3, then perhaps your SNR is not what it should be!! Start moving things away from your ignition system wiring to determing what is causing the problem. Check your spark plug to see that the correct gap is there and that the plug is clean and in good shape. Check your other ignition system items to be sure all is in good shape (wires, grounds, connections, coil, etc.).
I hope this helps someone. It's a lot of info, I'll have to review it a few times to check for errors and edit it to fix them.
---
Rich |
