Hello all
The last in the series of articles on light aircraft audio was published this month. This time it was about installation. Any comments and thoughts you have are welcome.
Ian Fraser
Wired for Sound article in March magazine
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Wired for Sound article in March magazine
Ian Fraser
019212
019212
Re: Wired for Sound article in March magazine
The article in the March magazine was most helpful with great advice as to planning from the block diagram through to the design detail of the harness. I shall definitely use the modular approach in the future.
Screening was mentioned, with some manufacturers specifying a strange arrangement where each connection has two wires (signal and common) and an extra screen is added. It was pointed out that this was not always necessary if the input common and the device's ground were electrically connected. The use of cheaper and lighter cable without a second common return wire seems good advice in a metal aircraft.
I used this approach in a wooden aircraft and found some problems with electrical noise. The first was noise from the alternator and the turn and slip motor in the audio from the radios. With a single signal wire, it seems that the signal common was being shared with the power return of the other aircraft systems through the limited ground network, injecting noise. The second problem was RF noise pickup from the transponder transmission (clicking). These were solved by connecting the signal common and using shielded cable, the shield being grounded at one end for RF. A second shield grounded at both ends may be needed if there is a requirement for lightning protection in a certified aircraft.
Hope this helps if someone is struggling with noise problems.
Screening was mentioned, with some manufacturers specifying a strange arrangement where each connection has two wires (signal and common) and an extra screen is added. It was pointed out that this was not always necessary if the input common and the device's ground were electrically connected. The use of cheaper and lighter cable without a second common return wire seems good advice in a metal aircraft.
I used this approach in a wooden aircraft and found some problems with electrical noise. The first was noise from the alternator and the turn and slip motor in the audio from the radios. With a single signal wire, it seems that the signal common was being shared with the power return of the other aircraft systems through the limited ground network, injecting noise. The second problem was RF noise pickup from the transponder transmission (clicking). These were solved by connecting the signal common and using shielded cable, the shield being grounded at one end for RF. A second shield grounded at both ends may be needed if there is a requirement for lightning protection in a certified aircraft.
Hope this helps if someone is struggling with noise problems.
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