ACK E-04 ELT

What is everybody using for a ground on the ELT. Two wires are supplied (shielded WH-F395 GPS data Out and WH-P325 ELT power). I've been told to braid off the shield and use it to ground the ELT. I've always understood not to land (ground) the shield at both ends of a wire and not to use it as a signal (current) carrying wire.

You already have a ground.. Your shield rule doesn't work for antennas, where the shield must carry current. So the antenna coax must be grounded at the base of the antenna, and at the box.

ELT Ground

Thanks Bob. It's not the antenna that I've trying to ground but the pin #3 on the ACK plug

PMLviator said:

Thanks Bob. It's not the antenna that I've trying to ground but the pin #3 on the ACK plug

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Put an ohmmeter between pin 3 and ground, I'll bet the pin shows that it is already grounded, via the braid on the coax going from the board ground to the airframe ground at the base of the antenna.(The coax won't work correctly unless it is grounded at both ends like this.) Unplug the coax, pin 3 will show infinite resistance to ground then, unless some mounting screws are grounding the circuit to the airframe.

If you sleep better at night with two grounds, run a wire from pin 3 to your ground buss. There's a small chance the ground loop may introduce some noise in audio circuits, but I doubt it.

PMLviator said:

What is everybody using for a ground on the ELT. Two wires are supplied (shielded WH-F395 GPS data Out and WH-P325 ELT power). I've been told to braid off the shield and use it to ground the ELT. I've always understood not to land (ground) the shield at both ends of a wire and not to use it as a signal (current) carrying wire.

Click to expand...

The ACK E-04 that I acquired has the ant jack (BNC), a flat telco cable with a rj-11 jack for the control head, and a flat telco cable with a molded DIN plug that connects power, ground and rs-232 GPS signaling. The instructions have the installer fabricating a 3-conductor shielded cable to connect to power and the GPS. Pin 1 is for power, pin 2 is for the test lead (rs-232 out/tx), Pin 3 is ground, and Pin 4 is rs-232 in/rx. The instructions imply the the cable shield should be connected to a shield ground. In my installation, the Wh/org conductor is power; Wh is rs-232tx (which is connected to pin 4); Wh/blu is ground; and pin 2 is a short test lead. The cable shield is grounded to the backshell of the device providing the GPS signal.

As best I recall, I just ran a ground wire to an existing screw that was in the vicinity of the ELT. Any fastener will do, just check continuity to ground (any bare metal on the airframe) when you're done.

I have not had any noise issues. I'll try to remember to look at my installation when I'm at the hanger on Monday.

I did the same as Rick. The magnetic reed switch for the right wing pin grounds to a screw located close to the ELT. Put your ELT ground wire on the same screw. Worked fine for me.
Alex

WH/blu wire

maus92
I have the WH/ORG power and WH rs232 but where did you get the WH/BLU ground wire?
Thanks guys about using a separate wire to a screw,I'm not worried about noise on such a short run.

ELT ground

I was not sure what to do about the ground.
The ELT instructions ask for a groundwire to be installed but Vans instructions do not mention it.
I looked at the wiring diagram and noticed that only the wire shield is connected as ground at the ELT plug without a separate ground wire at that location.
The shield of that wire is grounded somewhere in front of the plane.
I hope I did the right thing only connecting the shield as ground,without an additional ground wire at the ELT,since I have already sealed the plug.

Ueli N said:

The ELT instructions ask for a groundwire to be installed but Vans instructions do not mention it.

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Working from memory here, but I believe that Vans instructions refer to doing the installation per the [ELT] manufacturer instructions. The ground wire in question is in the ACK booklet.

This was one of the rare instances in the RV-12 instruction where there is a detail that was missing.

Yes Rick you're right, follow the instructions from the ELT manufacturer, fig.13 But I still only have two wires from the Skyview harness. BTW how's your sells going any bite's

PMLviator said:

Yes Rick you're right, follow the instructions from the ELT manufacturer, fig.13 But I still only have two wires from the Skyview harness. BTW how's your sells going any bite's

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Leon, The wires from the Skyview harness should be the power and GPS output. Power goes to Pin 1 on the ACK connector and GPS out goes to Pin 4. The Ground wire is not in the harness. You make it up yourself (#22 will work fine).

Thanks for asking about my 12. I had one very strong prospect but he backed out because he developed a fear liability associated with Experimentals in general. I think he was just over thinking the whole thing and got some bad legal advise.

I think it will be more appealing after it's painted. In the mean time, I enjoying flying the 12 and getting to play with the G3X system.