J

John Courte

Well Known Member
I've read the various threads on the subject, and it seems to be universally agreed that grounding your PTT button at the airframe is a bad idea.

I wish I'd known this before I ganged all my ground wires in my Infinity stick grip together before running them all out the bottom of the stick tube. So what I have now is a very nice, well-run, organized, and catalogued wire bundle that's probably wrong.

My audio panel is a GMA340, and since that's a fairly modern piece of equipment, is there any hope that I can get away with shorting the mic key circuit to airframe ground via the PTT switch? All the shields for everything else are grounded at the audio panel frame, per manual.

I'm trying to avoid both ripping apart my stick wire heat shrink tubing where it exits the stick as well as running two more twisted pairs forward and out to the mic jacks for the traditional mic key/mic return short the diagram calls out.

I think I probably know the answer to this, but maybe an expert or two can confirm or deny.

thanks,
-John
 
I know you will get a lot of responses contrary to this, but I've had my PTT grounded to the airframe for over 18 years and it's always worked perfectly.
I've also done this on every other airplane I've built. Never been a problem.
 
Although "best practices" say to never rely solely on the airframe as any electrical ground, there are an awful lot of planes out there, both E-AB and factory built, that have been using airframe grounds just fine for a very long time. Myself, I prefer to use deliberate ground circuits wherever practical, especially after encountering a couple of issues with engine sensors that were remedied by adding dedicated ground wires.
 
I consolidated all of my ground wires from the Infinity grip and went to a single airframe ground. I have only flown 200 hours over the last year with it but so far all is good.
 
Just as Mel, Paul and others, my PTT goes to the airframe and have had zero issues but its been only about 350 hours on the plane so I guess we will see.

good luck
 
The PTT line is an exception to the usual noise sensitive audio lines of a nav/com radio or intercom.

It is really a logic signal, and in older radios just provided a ground to a physical relay that switched comm. modes from Rx to Tx. In modern radios it will activate a solid state relay equivalent and should not be noise sensitive.

It really is the exception...:)
 
OK, sounds to me like it's worth the risk of leaving it as is and there's probably nothing to worry about.

I'm going to file this one under "build on." :)


Thanks!
 
Just to echo what the other guys have said - yes, PTT is the exception.

Grounding any wires that carry signals (be it audio or data) is a no-no but the PTT is just a logic switch. It won't be affected.

Cheers,
Matt
 
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