Mix power & serial conductors in multi-core cable?

pmerwood

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Wellington, New Zealand
Best practice question - for serial connections to the SV-XPNDR-261, SV-ADSB-472 and SV-GPS-2020 is it good practice to run the TX/RX conductors in the same shielded multi-core cable with the power connections for each device? Or, should the TX/RX conductors be in their own 2-core shielded cable and the power conductors run as individual wires? Thanks

Peter,
 

Rhino

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Jul 20, 2009
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Really depends on how you want to do things. As a general rule, it's a good practice not to run power alongside signal lines, analog or digital, but that isn't always an easy thing to do. The Dynon cables aren't shielded, but they assume the power wiring is routed separately, at least at some point, because it goes to a different place. It's also generally a good practice to shield any signal lines, but that's less important for digital. Digital signals are less susceptible to induced noise from power wires than analog lines are, so that's probably why Dynon didn't see the need when building their cables. In most instances, it probably wouldn't be necessary, but many builders opt for some level of overkill just to be on the safe side. Personally, I would probably run the data wires in a separate shielded line, and would definitely use a different path where feasible. But I freely admit the shielding probably wouldn't be necessary. It's really up to you.
 

pmerwood

I love flying!
Joined
Mar 4, 2017
Messages
22
Location
Wellington, New Zealand
Really depends on how you want to do things. As a general rule, it's a good practice not to run power alongside signal lines, analog or digital, but that isn't always an easy thing to do. The Dynon cables aren't shielded, but they assume the power wiring is routed separately, at least at some point, because it goes to a different place. It's also generally a good practice to shield any signal lines, but that's less important for digital. Digital signals are less susceptible to induced noise from power wires than analog lines are, so that's probably why Dynon didn't see the need when building their cables. In most instances, it probably wouldn't be necessary, but many builders opt for some level of overkill just to be on the safe side. Personally, I would probably run the data wires in a separate shielded line, and would definitely use a different path where feasible. But I freely admit the shielding probably wouldn't be necessary. It's really up to you.
Thanks. That's the conclusion I'd come to.
The SV-XPNDR-261, SV-ADSB-472 will be mounted beneath the seats in my Vans RV-6 and the SV-GPS-2020 will be mounted on top of the fuselage midway between the tail and canopy. For these long cable runs I've decided to use two-core shielded cable for the TX/RX conductors to each device and separate power and earth wires. It's not easy to separate the power and data conductors but I'm thinking if the data conductors are shielded that should suffice.

Peter,
 

Rhino

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It should, yes. If you can get shielded cable with the data lines twisted (twisted pair), that's even better. It reduces both induced noise and crosstalk.
 
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