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V16 audio shields - ground location
Posted: Mon Oct 02, 2023 2:43 am
by drancourt3
Hello,
I just got a V16 radio and currently making the harness (I'm new to that radio)
On page 15 of the installation manual, it shows that the shields of the audio wires should be grounded on pins 2,11,13 (headphones or microphones). I was a bit surprised and expected the shield to be grounded on the aircraft ground or power supply ground. Are both options equivalent ?
Thanks
David
Re: V16 audio shields - ground location
Posted: Mon Oct 02, 2023 7:55 am
by rainier
The shield should be grounded on one side only (so no current can flow through the shield). The shield should connect to a ground that is referenced to the most sensitive piece of equipment - as that equipment will use that ground as reference.
In this case the most sensitive piece of equipment is the radios microphone input. So we would like to use the same ground this uses.
Consider what could happen if you use another ground. Lets say the radios ground differs form that of the shield from a high frequency point of view. If the ground is physically far away and just dependent on how your ground are wired and what kinds of equipment are connected it is highly likely that the grounds are different - what I mean is if you connect an oscilloscope you will likely see a surprisingly complex signal between the shield and the ground of the radio. Since the shield is capacitively as well as inductively coupled to the cores it shields - this signal will easily couple to those cores and they will be seen as actual signal at the microphone input.
If you use the microphone input ground (or any signal ground on the radio which is the same) then this does not happen.