[NSRCA-discussion] electric interference question

[Bob Richards]

"Black Magic"? Hmmm. I hope not! :-)
   
  Ferrite beads are a way of reducing the common mode RF currents on a cable. The problem *might* be common mode, it might be differential mode. Without some expensive equipment (current probe and spectrum analyzer) it would be difficult to determine. Placement of the beads, and the type material they are made of, can have an impact on the results.
   
  Troubleshooting something like this is a process of elimination. The first thing I would do would be to use a seperate airborne rx battery, being sure to isolate the BEC in the ESC. I would use a seperate pack anyway, for the reason mentioned, unless you have to meet the weight restriction. However, even with a seperate battery, you still have the black and signal lead from the rx to the ESC.  If this does not cure it, then I would use a servo cycler of some sort to drive the ESC directly, with no physical connection between the radio and electric system.
   
  If the problem still persists, then you can be assured that the problem is radiated in nature, IOW the coupling path is radiated from the electric system to the radio. It would be best to try to attack this problem at the source (motor, esc). Try the ferrite beads on the leads to the motor (all three leads going through a single ferrite), and to the battery. The reason is that if the coupling path is radiated, it could be picked up by the antenna lead of the rx, and you certainly don't want to put a bead on that!!!
   
  If you do determine that the problem goes away when the electric system is running, but not connected to the rx, then the coupling path is through the BEC circuit (conducted path) which can be filtered different ways, with beads being one option but probably not the best. Using an opto-isolator would probably be the best, but a small filter network might also work well and cost less.
   
  On the other hand, if the ground range is being reduced by 5% or less, I probably would not worry about it. JMHO.
   
  Bob R.
  

John Pavlick <jpavlick at idseng.com> wrote:
    BTW - Any problem that can be solved with Ferrite beads is in fact Black Magic. It's right up there with coiling the scope probe lead in the opposite direction to get a cleaner signal. Who says this is a digital world? <LOL>
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