Control stick Wiring - what to do with shield?

[Rupester]

I have a shielded 4-conductor wire running from the control stick to the panel area for PTT, flip-flop, etc. I'm not sure what to do with the shield. (I have no diagrams to tell me, nor could I find anything with a Forums search.) I know sometimes you ground only one end of a shield; other times it's handled differently. BTW, one of the four insulated conductors is a ground running to the ground bus on the firewall.

How do I terminate the shield on that wire?

[rleffler]

Originally Posted by Rupester

I have a shielded 4-conductor wire running from the control stick to the panel area for PTT, flip-flop, etc. I'm not sure what to do with the shield. (I have no diagrams to tell me, nor could I find anything with a Forums search.) I know sometimes you ground only one end of a shield; other times it's handled differently. BTW, one of the four insulated conductors is a ground running to the ground bus on the firewall.

How do I terminate the shield on that wire?

Use something like:



These allow you to terminate shields. You can find them at SteinAir. They come in a variety of sizes.

[Sid Lambert]

Ground the shield at the audio panel/intercom. I don't think it is imperative to shield the PTT though. I did because it's the only 2 wire I had.

Originally Posted by Rupester

I have a shielded 4-conductor wire running from the control stick to the panel area for PTT, flip-flop, etc. I'm not sure what to do with the shield. (I have no diagrams to tell me, nor could I find anything with a Forums search.) I know sometimes you ground only one end of a shield; other times it's handled differently. BTW, one of the four insulated conductors is a ground running to the ground bus on the firewall.

How do I terminate the shield on that wire?

[Rupester]

Do I ground the shield only at the audio panel end, and NOT the stick end? (I have a 5-contact terminal strip at the base of the stick, at which I could ground the shield if need be)

[Sid Lambert]

Correct, never ground a shield on both ends. One end only and preferable all at the same place. The intercom/audio panel makers like it to be shielded there.

The purpose of the shield is to stop it from becoming an antenna of sorts. Think wave length. If the wire is 4 foot long then it gets in to COMM frequency. If it's unshielded for 4 inches it would be in a very high frequency that couldn't be heard. So that little bit of unshielded wire at each end won't be heard.

A very smart friend (crazy Electrical Engineer) coached me on this when I recently rewired my airplane.

Originally Posted by Rupester

Do I ground the shield only at the audio panel end, and NOT the stick end? (I have a 5-contact terminal strip at the base of the stick, at which I could ground the shield if need be)

[Sparky]

None of the wires in the control stick (PTT, trim, etc.) really need to be shielded, but it can't hurt. I would just ground the shield at the base of the stick since you have the means and are already using shielded wire.

[Rupester]

I found several references that said shielded wire on the control stick "bundle" was a must, thus I ordered the 4 cond-shielded wire for this specific purpose. Oh well ... live and learn.
Thanks for the advice herein. Tis most helpful.

[Trevor778]

you can even use the shield to provide the ground for your ptt if you need an extra wire. None of the wires going up your stick should need to be shielded, you could just dead end it with heat shrink and carry on.