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Radio interference. Radio noise, or ignition shielding
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Other related articles: Aircraft
Strobe Noise |
MF-3 Aircraft Magneto Filter
Another magneto filter is the Lonestar LS03-01010-04 (available at Sky Ranch)
| Another source submitted by Jim Weir, VP Engineering, RST
Engineering.
Radio noise that goes up and down in whine with engine RPM can also be
caused by ground loops between the headset jacks and the audio panel/radio
system.
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Radio noise that crackles is from the ignition system.
1. Faulty ignition harness shielding. Check for broken shielding. On Slick harness make to clean the silicone covering off the spark plug end of the wire so that there is good electrical contact between the wire braid and the spark plug attachment hardware.
2. Poor harness electrical grounding. Check ferrule assembly for integrity. Replace if it isn't tightly secured at the magneto cap or spark plug end.
3. Harness clamps or tie wraps too tight, crushing wire.
4. Dirty spark plug inner barrel or failed spark plug resistor (as evidenced by burnt contact button in spark plug barrel). This link has more details.
5. Broken harness shielding at spark plug end. As spark plug is installed or removed, wire is allowed to turn, breaking shielding.
6. The Bendix "Dura-Blue" ignition harness creates ignition noise due to insufficient seating of one or more of the tapered ferrules which provide a grounding path between the ignition cable shielding and the magneto cover or adapter plate. Refer to Bendix Service Bulletin 603 dated November 1978. This bulletin addressed a problem that existed back in 1978 and the problem has probably long since been corrected. However, it does illustrate the importance of achieving a good ground between the ignition lead shielding and the harness cap to prevent radio noise. Download copy of SB603
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