OK. This is all the installation info that comes with my LED lights (nav, position, strobes). To connect this I simply use a 4 conductor wire like this ? Then I ground the shield only at one place, at the main bus in the cockpit compartment for instance?
That looks good.
Where the shield is grounded doesn’t matter because it’s not carrying any current. You are not using it for the DC ground. I would ground it to the airframe at both ends. It’s only purpose is to prevent radiation of any interference which gets conducted into the wires inside the cable. For example typical aircraft LED lamps use a switching power supply inside and that will generate interference which will be conducted into the wires feeding the lamp.
Myself would begin by trying non-shielded cable, saving both cost and weight. Or, if it must be shielded, use the shield for the ground connection to that 3 conductors do the job – still saving some cost and weight. Then again, I would not use the tefzel stuff anyway, but that is up to the builder to decide.
I would shield everything, to give VHF comms the best chance of working in the presence of the various switch mode power supplies.
In a non radio aircraft it of course doesn’t matter.
Troubleshooting interference after the job is done is a huge task.
The weight of the wire is irrelevant.
If one used the shield for the DC return then one must not ground it to the airframe otherwise unless one is very careful some of the ground current will instead flow through the airframe and then you create a magnetic loop which will bugger up the compasses.
That 4 conductor tefzel wire doesn’t cost much, $0.86 per feet. I need about 20 feet.
You may want to consider the voltage drop in it if you have lights that draw a few amps. Ohm’s law, etc. However this issue is not big nowadays. My LED lamps draw 1.5A each (24V).