GTN650 GTX330ES signal wire and grounds

[jeffsvan]

This is a question about using shielded cable, grounding the shield, and using ground wire.

Just trying to get a feel what the majority of you did during your install.

I connected my flight plan out (GTN650) to my Aero 660 portable.
I connected "just one wire" as some of you instructed. It works fine. No shield, no ground.

I now need to connect ADSB out from the GTN650 to an input on the GTX330ES transponder.

I also need to connect serial altitude out from my Encoder to the GTX330ES transponder.

Several folks here are saying "all you need is one wire for each". But the manual is showing I need to use the signal wire, a RS232 ground wire, and shielded cable.

What is the correct answer? Can someone please go into detail

[RV6_flyer]

One wire MAY work.

To get a good signal, one needs a good signal path and a good ground path. The ground path may or may not be there and may or may not be good without the extra ground wire. The ground wire insures that you have a good return signal path.

As for the shielded cable, typically that will be required in a noisy environment. IF you do NOT have any electrical or RF noise in the environment that the equipment is being used in, you MAY be able to save the weight, expense, and extra man power leaving it out. Sometimes, a twisted pair wire will provide enough noise rejection that the shield will not be necessary.

I am one of those lazy people that typically put in the best installation possible by using a shielded twisted pair cable up front. By using the best practice up front, I save labor time and money by not having to do the job twice.

Teaching hat off.

[az_gila]

The RS-232 signal levels are pretty much immune to low levels of interference -



A good technical description here -

http://electronicdesign.com/what-s-d...ial-interfaces

A ground would help, but unless some large voltage spikes are around and your cable length is long, then the shield should not be needed.