Push to talk wiring

[Jerry Carter]

Almost done with wiring, but I need a little help on wiring the push to talk switches. My Stark-supplied harness has two bundled wires of six wires each coming from the PMA9000X audio panel for the headphone and mic jacks. I have wired the phone jacks with no problem. The three wires for each of the mic jacks are labeled Hi, Lo and Key. I understand where these wires go on the mic jacks. My question is where to put the PTT wires from the sticks. If I attach one of the wires to the key terminal on the mic jack along with the other wire from the audio panel, where does the other wire from the stick go? Can it just go to aircraft ground, or should it run to the mic jack and attach to the common terminal there?

I can call Stark tomorrow, but I thought the issue may come up for others, too.

Thanks!

[L.Adamson]

The PTT wires go to key (which is labeled on a PS Engineering schematic as Pilot/Co-pilot PTT) & mic lo.

I just recently installed a PS Engineering 8000B. It works great.

edit. That means two wires soldered to two terminals on the mic jacks

L.Adamson ---- RV6A

[Jerry Carter]

Thanks for the quick reply!

[breister]

Just to complete the thought:

"Low" is actually a ground. If you wire the PTT wire onto the mic receptacle, it is assumed you are using the sort of headset with a PTT switch on the cable. Most of us mount a remote PTT switch on the stick or throttle quadrant, so that is where this wire needs to go - and the PTT switch therefore needs a ground wire returning to the same ground source used by the audio panel to avoid stray electrons.

[Jerry Carter]

Originally Posted by breister

Just to complete the thought:

"Low" is actually a ground. If you wire the PTT wire onto the mic receptacle, it is assumed you are using the sort of headset with a PTT switch on the cable. Most of us mount a remote PTT switch on the stick or throttle quadrant, so that is where this wire needs to go - and the PTT switch therefore needs a ground wire returning to the same ground source used by the audio panel to avoid stray electrons.

So, if the audio panel is grounded at the firewall ground block, I can just run the second wire from the stick to the firewall ground block? And the other wire attaches to the PTT terminal of the mic jack along with the PTT wire from the audio panel?

[L.Adamson]

Originally Posted by Jerry Carter

So, if the audio panel is grounded at the firewall ground block, I can just run the second wire from the stick to the firewall ground block? And the other wire attaches to the PTT terminal of the mic jack along with the PTT wire from the audio panel?

That's the method that my SoftCom intercom used. And for all I know, the mic lo pins might just go directly to the radios ground also. However, I just used the wiring diagrams supplied with the audio panel. For instance, the "mic swap" switch just grounds to the aircraft, rather than returning to a audio panel pin.

L.Adamson

[breister]

Originally Posted by Jerry Carter

So, if the audio panel is grounded at the firewall ground block, I can just run the second wire from the stick to the firewall ground block? And the other wire attaches to the PTT terminal of the mic jack along with the PTT wire from the audio panel?

Yes. Theoretically, any other perfect ground would work, too - but grounds in real life are funny. Small changes in resistance / location can cause weird effects. I don't know how sensitive the PTT is to these effects.

[Alan W.]

Always run all mic / headset / PTT grounds to the same point as per the reason stated by breister

[Walt]

Any good ground is ok for the PTT.

[Rodney]

Wired PTT and shows TX but sidetone goes away and doesn’t transmit.
Two wires to PTT. Does it matter which wire goes to which terminal on switch ?