Ok, you have convinced me to do away with the bellcranks on my 51 and install servos in the wing. My next question is.. I`ll have to use a Y harness and extension since the servo lead will be about 6 inches short of reaching the center of the wing. How long can I go without needing an amplifier or some kind of help without worring about signal loss?
Wait, when you say "ground" you mean the negative side of the battery yes? The same negative as is travelling along one of the 3 wires going to the servo already? Or do you have some kind of earthing system on your aircraft? Also, when you talk about 4 conductor cable, do you actually mean shielded cable?
Thibk of a long pice of wire. Makes a great aerial doesn't it? How DOES it do that since its so thin...and has no effective aera to cover?
Well the tiny currents induced in teh wire by the signal, make a field of their won that radiates out, and cancels the signal all around. So an aerail that is a stragight piece of wire can pick up signals that actually when you measure the power, would seem to come from a big chink of space. If you tune the aerial to the signal you want, the effect is even better.
Now think that this aerial is earthed to the reciever. It sort of damps down energy, directing it to ground, in the vicinity. Not as good as a screen, but still a lot better than nothing. In fact its SO close to the other wires that there is quite a bit of capacitance directly between them, so that shorts out spikes a bit as well.
The maths is horrendous, and I have forgotten all of it, but I remembered the result - derived I think via tensor calculus from Maxwell's equations - but the result - that a load of earthed conductor near 'hot' wires gets rid of interference, is well known and proven.
Whether its the capacitance or the EM effect that dominates depends on geometry. My guess is that capacity does in this case. BUT it also stops the servo wires picking up other stuff that is floating around, and injecting it into the receiver...screening would be the ideal ion this case.