Intermittent transmitting

[Mcstealth]

My radio(430) is now making it a habit of not transmitting all the time. Interestingly, it does not seem to affect the receiving side of the equation. 

I was on the taxiway, and I could not transmit. I did the run up and I heard in the headset a "change" and I could transmit. During the flight, it was on again, off again with being able to transmit. Upon landing, nothing all the way to the hangar. 

I do not think it is the PTT button because it seems to be doing its job and using the right seat button makes no difference. 

Any thoughts?

 

[N201MKTurbo]

Do you see the transmit indication on the radio when it isn't working?

[N201MKTurbo]

Does your sidetone change?

Have you tried cleaning your headset plugs?

[Mcstealth]

1 hour ago, N201MKTurbo said:

Does your sidetone change?

Have you tried cleaning your headset plugs?

Side tone does change when PTT is engaged. When I push/pull the volume button, the "rx" icon does appear. Don't remember exactly if the ""tx" shows when PPT is engaged. Will confirm that today. 

[N201MKTurbo]

Your sidetone changes when you transmit, it changes from intercom sidetone to radio sidetone.

What I was asking is, does the radio sidetone change when you are having trouble transmitting and when transmitting is working?

[Mcstealth]

17 minutes ago, N201MKTurbo said:

Your sidetone changes when you transmit, it changes from intercom sidetone to radio sidetone.

What I was asking is, does the radio sidetone change when you are having trouble transmitting and when transmitting is working?

Affirmative. Sidetone does change when PPT is engaged but no transmission happens. Tone goes back to "normal" when PTT is disengaged. 

[MikeOH]

42 minutes ago, Mcstealth said:

Affirmative. Sidetone does change when PPT is engaged but no transmission happens. Tone goes back to "normal" when PTT is disengaged. 

I may not be following correctly, but I think what @N201MKTurbo is actually asking is if, when the PTT is depressed, is there is a difference in the sidetone when transmitting successfully and when you can't transmit; not the difference in sidetone when you release the PTT (that's when it goes back to the intercom sidetone).

[Mcstealth]

1 hour ago, MikeOH said:

I may not be following correctly, but I think what @N201MKTurbo is actually asking is if, when the PTT is depressed, is there is a difference in the sidetone when transmitting successfully and when you can't transmit; not the difference in sidetone when you release the PTT (that's when it goes back to the intercom sidetone).

Yes. Sidetone changes when trying to transmit, but nothing comes out. I don't hear myself in the headset. When the issue is happening the sidetone does "click" correctly when pressing the PTT but the tone is different and nothing transmits, nothing comes out from my microphone. Also and I forgot to mention,  when the issue is happening, nothing is heard in my headset from my micrphone at all when the PTT is engaged.  When I hit a bump in the air, I hear a  click  and the system works for a second or two, or five minutes until the next bump in the air. 

[MikeOH]

Since your mic and sidetone work properly when in intercom mode and the intercom 'cuts out' when you key the mic, I think you have an intermittent mic wiring issue between the intercom and the radio.  I suspect you are keying the transmitter (need to verify the TX indicator is active) but the mic signal is not getting to the transmitter.

Have you tried reseating/reracking the 430?  Probably a long shot, but easy to try.

[PeteMc]

The Transmitter and Receiver are different circuitry.  So you could be hearing the side tone and still not be able to Transmit.  You could actually be hearing the Side Tone through your Intercom too.  Also, how's your voltage?  It takes a lot more power to transmit than it does to receive.  So maybe something with the Voltage Regulator? 

First I'd loosen the radio and slide it in an out a few times (5-6) and then tighten it back in and test it again.  Next it sounds like a Bench Test is in order.   If you can get your hands on the same model you have you can also slide it in to confirm the backplane connections, etc. are all good and that the issue is in the radio. 

 

Edited April 15, 2024 by PeteMc

[PT20J]

Depending on the configuration there can be a lot of possibilities because the intercom and audio panel are also involved.

1. What year and model airplane are we talking about?

2. What audio panel do you have?

3. What intercom do you have?

4. Do you have Emergency phone and mic jacks?

5. Do you have a hand mic?

6. Do you have a second com radio?

[N201MKTurbo]

So it sounds like you have an audio issue. The sidetone while transmitting is typically taken from the modulator, so it is as close to the final amplifier as possible.

As stated above, I would start by reseating your radio and your audio panel. The fact that a bump in the air will cause it to change, indicates that it is a mechanical bad connection. Usually at a connector. Reseating them will often fix this.