I'm fairly savvy when it comes to basic on-off, DC Circuits, but I'm at a loss for Audio circuits, hoping someone can help explain this to me. I am an amateur Radio enthusiast and enjoy the hobby, as well as tinkering. My latest venture is to create a connection cable that goes from my handheld radios headset/mic/PTT port (3.5mm TRRS) into my mobile phones headset jack (3.5mm TRRS) I have the pinout of both, ends, and I have tried a little circuitry, but I'm not getting anywhere but frustrated. I don't care about the PTT, circuit, I will manually key the handheld, I just want to be able to transfer audio back and forth without outside noise interfering. Attached is what I have that failed.

Any help is greatly appreciated.

 

Could you describe what is happening? You say it’s not working but what does that mean?

It would help to know what you’d like to have happen, exactly, and what is happening instead.

 

Hi Blupanthr2, just to clarify again, you want to feed the audio output from one device into the micro-phone input of the other?
The main problem will be that the audio out signal will be quite powerful and amplified, but the micorphone signal that is expected will be very weak and low voltage, (for computer etc. you use the "line-in" connection, for inputting an already amplified signal.) I am sure if you google it someone will have done it already. But you might try feeding the audio signal in via a resistor or potential divider, to reduce the voltage to something more approaching a microphone signal.

 

But you might try feeding the audio signal in via a resistor or potential divider, to reduce the voltage to something more approaching a microphone signal.

He might need an L-pad in there, but it’s hard to tell yet because whatever the failure is, he’s yet to say.

Really, this should be trivial, so knowing what the problem is will probably clear it up.

 

Hi, Sorry, What is happening is, I am not receiving any audio going from the Phone to the Radio, it is just quiet, even though a continuity tester says the wiring is correct, and there are no shorts. Going the other direction, whenever the radio emits sound, the Phone speaker volume control goes up and down, and sometimes to mute. (very bizarre) I suspect it may have something to do with the fact that the phone reads different resistor values based on buttons being pressed maybe? I did try to put a 10k ohm resister inline on the Phone Speaker to Radio Mic, but still no audio. It's almost like the phone doesn't recognize a device is connected to it.

 

Hi, Sorry, What is happening is, I am not receiving any audio going from the Phone to the Radio, it is just quiet, even though a continuity tester says the wiring is correct, and there are no shorts. Going the other direction, whenever the radio emits sound, the Phone speaker volume control goes up and down, and sometimes to mute. (very bizarre) I suspect it may have something to do with the fact that the phone reads different resistor values based on buttons being pressed maybe? I did try to put a 10k ohm resister inline on the Phone Speaker to Radio Mic, but still no audio. It's almost like the phone doesn't recognize a device is connected to it.

The symptoms you are describing sound like there is a possibility the phone connector pinout you are using is wrong. The volume changes sound like your capacitor is not AC coupling the input to the phone for some reason. The fact that you are not getting input to the radio would tend to suggest you are not getting output on that line from the phone.

I would do two things: first, I would unplug the cable from the radio and see if you get audio on the connector from the phone on the first ring of the radio connector as you are expecting. I would also try to AC couple both lines since they are both trying to provide bias for a condenser microphone.

The diagram you are using is for a TNC cable, and while the signals should be correct the TNC doesn't use control lines on the connector, nor does it provide mic power.

So, confirm each connector, when not plugged in, seems to produce the signals on the other end you'd expect.

What is the model of the phone? I have already checked on the FT-50, and Yaesu agrees with that pinout in the manual.

 

A little follow-up: I toned out a Yaesu supplied packet adapter for that connector and it seems to agree with the diagram. The connections to the TNC input are only common and speaker, and to the output are only common and mic, according to the TRRS pinout. So, for what it's worth, that's some confirmation on the Yaesu side.

 

whenever the radio emits sound, the Phone speaker volume control goes up and down, and sometimes to mute.

Perhaps the radio is over-driving the phone and the phone's AGC/protection can't keep up or cope.

 

You cant just put audio out into microphone in, its overpowers the microphone input. You need some sort of attenuation in place.

You need something like this:

(though why it takes him 10 minutes to explain it...!!)
(simple google search "audio out into microphone in"