Sharing headset inputs

[Topper]

i have a 340 audio panel and lemo + regular jacks for the pilot and co pilot. I am traveling and the PTT switch on the pilots yoke failed. Doesn’t sound like I am going to be able get it fixed before I head back home. I just switched headsets with my wife and reached over and used the co pilot switch. Perfect opportunity to get my wife to start using the radio, but she is not ready to take it 100%.

Any issues with impedance or anything else if I plug a lemo set and ga plugs in the co pilot side at the same time? This way we either of us can talk. Both mics will be live but that shouldn’t be an issue.

Thanks,
Jim

 

[bnt83]

no hand mic?

I don't think two mics can share a channel.

The other option is that maybe the PTT wire is actually wired to the mic jack, paralleled with the yoke PTT. If so a portable PTT switch could be plugged into the pilot's mic jack(s) and you're good.

 

[Topper]

I didn’t even think about the hand mic. I honestly don’t remember if it is in the plane. Thanks for the thought, I will use it if it is there.

 

[bnt83]

I didn’t even think about the hand mic. I honestly don’t remember if it is in the plane. Thanks for the thought, I will use it if it is there.

Its kinda funny, some of these old F900 for example have two hand mics, two crew+ headset jacks and even the oxygen mask mics.

 

[MBDiagMan]

Yes, connecting two headsets to the same channel would cause an impedance mismatch. I was warned about this by an avionics shop when they saw front and rear plugs connected to the same channel. It’s a two plac3 plane, so the idea was for both pilot and copilot could plug into front OR rear. After that warning I never tried it so I don’t know the car nsequences.

Sounds like mayb3 you need to head home with your headset connected to the copilot side and ask her to do without unless you want to use this for an opportunity to press her into stepping up her game.

Good luck!

 

[nrpetersen]

The Gods of impedance mismatches are generally quite benign. Try it & see what happens.

 

[flyingbrit]

This^^^^^^^^^
If you connect an 8 ohm headphone to a device designed for 600 ohm headphones you would have a problem, as this would be a 75:1 mismatch. The 2:1 mismatch caused by two normal headsets connected to one channel would likely work just fine.

 

[weirdjim]

The Gods of impedance mismatches are generally quite benign. Try it & see what happens.

WIth constant impedance things like earphones, you are correct. The parallel impedance will suck the audio level down a bit, but they should both be able to hear.

With microphones, not so much. The aircraft radio produces what is in effect a constant current generator and whichever microphone has the slightest impedance advantage will suck the current and the other one will be nearly unreadable. Sad fact of life until the whole world gives up on those stupid carbon microphone hybrid circuits that use a dynamic mic at the headset and morph it into the dinosaur of carbon mic simulation this will continue to be so.

We need a rather deep overhaul of our avionics standards. For years we have said that the AM modulation of our COM bands is mandatory since the weak signal response of an AM detector is better than an FM detector. Since the advent of phase locked loops and digitally defined radio. not true. FM or some digital format would be SO superior to the crackles and pops of the radio listening to the spark plugs would be a thing of the past. And we could actually go to plain old wire plug harnesses and resistor plugs just like the current stuff coming out of Detroit or Seoul or Taiwan. We are the dinosaurs of the transportation industry but there are lots of spark plug, radio, and other industries that have more dogs in this fight than you or I. Who is your Congresscritter going to listen to? You? Or ACDC spark plug company that can afford to give ten grand to a congresscritter's reelection campaign?

And please don't get me started on THAT rant. Know where the word politics comes from? The first part is poli, which is the Greek word for "many". And tics are just blood-sucking parasites.

Jim