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Clicking Sound in Headset

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JCurtis:
If powered from the aircraft, check the ground connection of the power supply. If you can measure it how many ohms between  ground at the power supply and the battery?

Sparky67:
Thanks all, some useful suggestions there. It’s going to be a couple of weeks now until I can get over to the hangar but will take those with me.

It’s easy enough to wire in an audio transformer (recovered from an old ADSL router) so will look at that first. There is some very low-level data noise present too, not too noticeable when the engine (O-200) is running, which that might help with.

We have an electronic reg, switching the dynamo field off makes no difference and the clicks don’t coincide with it stopping and re-starting charging. I did think about RF getting into the audio wiring so fitted bypass caps in the PAW audio amp. The P3i data bursts do sound about the right timing, but why so intermittent?!

I now have the parts to build a (5A max) analogue 12-5V converter and a heavier-duty USB power cable, so that will be trying that too - after soak-testing it on the bench. And I will certainly have a closer look at the Pi out of the aircraft.

Thanks again.

Martin

exfirepro:
Hi Martin,

Thanks for the feedback. I can’t at the moment think why the clicks (if PAW generated) should be intermittent. As you are obviously aware, electrical interference is usually specific to the individual vehicle/installation, but I will give it some further thought.

You obviously have a good handle on the issues involved and potential ‘fixes’. Please keep us ‘in the loop’ so we can all learn from whatever you may find.

Best Regards

Peter

Paul_Sengupta:
Sometimes the clicking caused by RF breakthrough from the PAW antenna into the audio system, can be intermittent depending on head position, etc, especially with ANR headsets which can be particularly susceptible to RF.

Sparky67:
It’s certainly a possibility Paul. If I knew when it was going to happen, and it lasted longer when it did, I could remove the P3i antenna connector and see if that stopped it. The connector is just accessible under the panel.

The dedicated supply for the PAW box has now been fitted (a deconstructed and hard-wired Anker unit as described on this forum) and the audio isolation transformer has been added between the PAW box and the audio amplifier. The intermittent regularly-spaced clicking hasn’t been reported since, although to be fair, the aircraft hasn’t flown many hours since the work was completed. So I’m keeping an open mind on a working result at the moment!

I’m also now wondering whether this could possibly be interference from electric fences. The airfield is surrounded by farm land and the clicks seem to be heard the most just after taking off, or on approach. Does anyone know how often electric fences pulse their volts into the wire? If it’s around two seconds I will go and look for one in the same area with an am radio!

Thanks.

Martin

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