Alternator noise!

15 posts in this topic

Posted

I've got a lot of winning engine noise in the headsets! I Beleive its my alternator, the noise increases with rpm. Can anyone tell me what noise suppressor I need for the 912ul alternator? I've read a lot about noise in the system and I've got a filter on the ignition. But I'm looking for a part specific #! Thanks!

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Posted

Have you changed your spark plugs lately? Is there an "R" within the numbers on the spark plug? Almost everything these days use resistor plugs but I still have many motors around that don't use them. It was common years ago to swap out plugs and spark plug wires to get rid of noise in car radios.

Info here on spark plugs and the "R" you may or may not have:  https://www.ngksparkplugs.ca/tech-info-spark-plug-faq.cfm

 

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Posted

Do you have the big electrolytic capacitor on the regulator per ROTAX? Are the wires short from the cap to the regulator and from the cap to ground? Does the regulator have a great ground?

Usually a whine is regulator and a buzz is spark related if you can tell the difference. You can't always tell.

Also i do not remember if the 912 uses resistor plugs or not (and I have one, i should know but I don't) I just buy the recommended plug. The recommended plug does not introduce ignition noise if everything is installed correctly.

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Posted

Thanks! I will check those things out!

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Posted

From what I've read the 22000 capacitor with the voltage regulator is to flatten the current leaving the regulator, not specificly a noise sepressor! I'm receiving whinning noise on the radio.

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Posted

Boy have I been thru this recently. My radios were very noisy and now they are completely quite. After trying several things it came down to four things that made the most difference. Ground: you have to have good grounds to your accessories and antenna. Coax: spent the little extra money and buy the RG400 double shielded coax from your radio to your antenna. You can buy it already put together in various lengths. Antenna: buy a quality antenna and make sure its grounded to a decent ground plane. I mounted mine to my turtle deck and ran separate grounds to the airframe because the fasteners did not provide a good enough ground. RF Noise Suppressor: I installed two different noise suppressors. I tried a smaller one on the power wire running the intercom but ended up buying and installing one to filter the whole system. I put it between the regulator and my main power buss. I bought the 30 amp one off of Ebay. Here is a picture of the kind I bought. This one pictures is the 50 amp but you get the idea. 

I'll say it again because it is the one thing that gave me the most issues...... You have to have good grounds to everything.

Hope this helps. 

Suppressor.PNG

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Posted

You are spot on with good grounds.  Run everything back to one ground buss then connect it to the battery.  If you use your air-frame for ground you will possibly have noise.

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Posted

You are spot on with good grounds.  Run everything back to one ground buss then connect it to the battery.  If you use your air-frame for ground you will possibly have noise.

TJay,

ok for one single, common, ground buss and not use the air-frame for ground. But the air-frame should still be connecte to the same grounf buss, right, or should the air-frame be insulated from the electric cirquit? 

Fred

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Posted (edited)

I usually keep the air-frame completely separate but you may have to run the engine block to the battery I wouldn't run that to a buss. Seems to keep all my stuff quiet. Not saying it will always work but has so far.

Everyone that i talked to said Jabiru and rotax have the noisiest alternators in them so i did use all shielded wiring and ran all the shielded covers to there own ground buss then ran that main shielded buss wire to the air-frame. So I guess I have one hot buss and two ground buses.

Edited by TJay

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Posted

Here is what I used on both of my planes.

http://www.bandc.aero/groundblock2424-tabfirewallkit.aspx

it mounts to the firewall and the ground wire from the battery and then the engine engine ground come off of the other end of the bolt.

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Posted

My plane has two ground points. The engine and main ground buss share a point on the frame at the firewall/engine mount and the Battery has its own point to the frame behind the seat. With the shielded plug caps, noise suppressor, good antenna and double shielded coax I was still getting noise. It was coming from the Belite LED gauge and was so loud it would drowned out the squelch on my radio. After grounding the turtle deck all is quite. 

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Posted

The 22,000 uf electrolytic capacitor filters / smooths the chopped DC from the gated rectifiers in the regulator and provides spike and noise suppression.  

Unfiltered ripple can be a very good noise generator.

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Posted

Like many I have been struggeling with static on the radio and after reading the posts on the topic I got myself a filter... A not too cheap (about 20 USD/Euros), very sturdy in a shielding metal case and I particularly liked the thick copper wires. How could this go wrong?

IMG_3232.thumb.jpg.36f4b3a7c8360923bbe32

The first impression is amazing new and different static in ADDITION to the old static...

I need to do some more investigation (install some switches so I can disconnect the filter and bypass it at will... )

To be followed...

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Posted

Fredstork, I had the same issue when I installed the larger filter. It ended up being the ground. to my antenna.

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Posted

Make sure your headphone jacks are isolated from ground.

John M

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