I have little insight on electromagnetic compatibility. Please help.
I have read Aero Electric Connection cover to cover, some of it four times. I know that I am supposed to keep wiring for DC power to stuff like motors separated from avionics, but am struggling with knowing what is what and how much they matter. I am trying to wire my fiberglass airplane with internal antennas properly.
Here is what we have in the aft fuselage:
Oh, just to make it interesting, I can pretty easily rout two bundles from the aft fuselage, but three or four will be a “challenge”, so I want to keep all this coppery stuff to two bundles if it makes sense to do so. Also, since aft fuselage is a pretty tight space, I really do want to do this just once. Rearranging it later is an exercise I would love to avoid... Rearranging wiring through the baggage bay and cockpit would still be a major pain, but a lesser challenge than the aft fuselage.
So, how do I bundle this stuff to stay quiet on signal and radios?
What say you guys? It sure would help if I can bundle the servo position signals with either the power wires or with the coax cables and still have it behave nicely.
Billski
I have read Aero Electric Connection cover to cover, some of it four times. I know that I am supposed to keep wiring for DC power to stuff like motors separated from avionics, but am struggling with knowing what is what and how much they matter. I am trying to wire my fiberglass airplane with internal antennas properly.
Here is what we have in the aft fuselage:
- Trim Servos – Two power wires to run a DC motor and three wires for servo position - high reference, low reference, and potentiometer. The maker puts all five 24AWG wires on a flat cable, no shield. Max 1 amp for power. Three sets of these, just to make it interesting. Is it wise to leave these cables whole or split them up into signal and power sets?
- ELT, has power, ground, and GPS data, all 22 AWG in a shielded cable gounded in the cabin, 1 amp fuse. There is also an RJ11 connector cable to the control box forward. No motors, just electronics;
- Three RG400 coax antenna cables, two TX/RX for COM, One RX for GS;
- Aft white and strobe, LED continuous and flashing - continuous 1 amp and momentary 6 amp. Powered by a two conductor 22AWG shielded cable, grounded in the cabin;
Oh, just to make it interesting, I can pretty easily rout two bundles from the aft fuselage, but three or four will be a “challenge”, so I want to keep all this coppery stuff to two bundles if it makes sense to do so. Also, since aft fuselage is a pretty tight space, I really do want to do this just once. Rearranging it later is an exercise I would love to avoid... Rearranging wiring through the baggage bay and cockpit would still be a major pain, but a lesser challenge than the aft fuselage.
So, how do I bundle this stuff to stay quiet on signal and radios?
- Does it work OK to bundle coax with power wires? Or will electric motors mess up the Voice and GS stuff?
- The makers of the servos and ELT seem to bundle up power and signal – should I keep them that way? Or should I separate power from signals as close to the servos as I can?
- The ELT instructions direct us to run power and data in the same shielded cable, so I am guessing they can stay together... Or do we run power for ELT and LED’s and servos together then bundle signals together and run them separately?
- Do I run coax cables together but away from a power bundle for ELT and LED and servos and away from signal bundles?
- I have a dipole on each fuselage wall that tends to use the whole vertical height available. I plan to run my wiring along the fuselage walls and through the center of the dipoles. That gives me a place for two bundles, not three.
- Putting a third bundle at say top or bottom of the fuselage has been warned against - Jim Weir says it will mess with my COM antennas. I could suspend a run of wiring down the middle of the fuselage, next to the big push-pull tube for the elevators. That only gets me about 4” separation between two of the bundles and would get interesting to work the support. A fiberglass wand supported at bulkheads and by some triads along the length could work. I do not have any desire to do that…
What say you guys? It sure would help if I can bundle the servo position signals with either the power wires or with the coax cables and still have it behave nicely.
Billski
