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plane has just developed a radio buzz on receive , the buzz goes up and down with the engine revs, volts look ok, replaced reg not that long ago, I have little knowledge when it comes to these problems, hoping someone can give me some ideas. engine is a 914 ,1350 hrs

 

 

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Iv'e heard that sound before!, can't recall wether a bad earth or a bad alternator diode, and don't forget alternators do have brushes.

 

also check the RF capacitor.

 

spacesailor

 

 

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Check the earth shield on the coax hasn't come loose at either the connector at the back of the radio or at the antenna mount. You can use a multimeter to check that out

 

Check the power connections to the radio - in particular make sure the ground connector is clean and making good contact.

 

Try adding a power filter to the line coming to the radio, which may help a bit.

 

 

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sorry, i should have said why to check that stuff. Most often those sounds of noise issues come about due to a grounding problem. Coax connectors are generally pretty reliable, however they can fail, particularly in high vibration environments. I said the power filter may help, but if its a ground issue then basically you have one (or more) part of the electrical system using a ground with a different voltage on it to the rest of the system. The power filter doesn't really address that problem, but if the underlying issue is dodgy power filtering in your radio, it might alleviate the issue a bit.

 

anyway, good luck.

 

 

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  • 4 weeks later...
  • 3 weeks later...

Not sure if it will help but I just brought a tranceiver and it came with a ferrite core to wrap the 12v cigarette lighter charger cable around. Meant to stop interference.

 

 

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Have you wound the radio squelch so far back it picks up all noise? That's a common mistake. You adjust squelch with the motor running so only your voice gets through. Start with the simple sh*t first. Is a hand-held radio close by picking up the noise? Disconnect the antenna - if the noise goes then the interference is coming via the power cable. Hard to help when I'm not there...

 

 

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All low voltage audio cables need to be shielded. The shield MUST be rather at ONE end only. If not you can get earth loops, they will be at a multi of the engine frequency, usually double.

 

 

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