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Capacitor Installation for Ignition Noise

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dwwilt

Joined: 06 Dec 2010
Posts: 192

Posted: Thu Apr 12, 2012 11:08 am Post subject: Capacitor Installation for Ignition Noise

I made a search of the forum and could not find this, so I am asking the group.



I have ignition noise in my radios.  I have the Jabiru 3300 in an Arion Lightning.  My radio stack has a PS-Engineering PMA5000EX with a SL-30 and SL-40.  I know where to install the capacitor on a standard type alternator, but the built in alternator for the Jabiru makes it kind of hard to decide where to put it.



Has anyone had this issue and solved it with the capacitor?  And if you did, how did you install it?



Thanks,

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Dennis

pete(at)usjabiru.com
Guest

Posted: Thu Apr 12, 2012 11:29 am Post subject: Capacitor Installation for Ignition Noise

I don't think a capacitor on the charging circuit will do anything for noise

from the ignition.  If the noise is from the alternator or regulator then

maybe it might help.  It sounds somewhat like you are trying to slice an

orange by cutting into a watermelon. (forgive my awkward attempt at humorous

analogy).



Pete



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BARRY CHECK 6

Joined: 15 Mar 2011
Posts: 738

Posted: Thu Apr 12, 2012 11:43 am Post subject: Capacitor Installation for Ignition Noise

Dennis:



What value is the capacitor?

Is it a low value such as 0.2 uF?

Or a high one such as 25,000 uF (or greater)?

The small value goes right next to the OUTPUT of the alternator.  Keep the leads SHORT.

 The High value - Well, there you have some options. You can put it right at the B+ Buss to Ground.  That way it removes the noise and filters all of the electrical system.

OR, you can also put it right at the alternator - The SAME as the low value capacitor.

 But there it will not do as much to remove noise entering the radios.

The BEST of both worlds is to use BOTH value capacitors... Small value at the alternator and the larger at the B+ Buss.

AND... One more trick... Install a ferrite (snap on) bead on the alternator wire as close to the battery as possible.  The bead must be a TIGHT fit over the alternator output wire.  

 Question: What type and where is the ACU (Alternator Control Unit) located?

Barry

Electrical Engineer



On Thu, Apr 12, 2012 at 3:08 PM, dwwilt <dwwilt(at)aol.com (dwwilt(at)aol.com)> wrote:

 [quote]--> JabiruEngine-List message posted by: "dwwilt" <dwwilt(at)aol.com (dwwilt(at)aol.com)>

  

 I made a search of the forum and could not find this, so I am asking the group.

 

 I have ignition noise in my radios.  I have the Jabiru 3300 in an Arion Lightning.  My radio stack has a PS-Engineering PMA5000EX with a SL-30 and SL-40.  I know where to install the capacitor on a standard type alternator, but the built in alternator for the Jabiru makes it kind of hard to decide where to put it.

  

 Has anyone had this issue and solved it with the capacitor?  And if you did, how did you install it?

 

 Thanks,

 

 --------

 Dennis

 

 

 

 

 Read this topic online here:

 

 http://forums.matronics.com/viewtopic.php?p=370618#370618

 

 

 

 

 

 

 

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vvkidd(at)mindspring.com
Guest

Posted: Thu Apr 12, 2012 3:37 pm Post subject: Capacitor Installation for Ignition Noise

Check out your grounds.  You must have a common ground to ensure a no noise 

enviornment.  

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dwwilt

Joined: 06 Dec 2010
Posts: 192

Posted: Fri Apr 13, 2012 12:43 pm Post subject: Re: Capacitor Installation for Ignition Noise

For a composite aircraft, I have fairly good grounds.  I have an Arion Lightning.  However, grounding is always an issue for composites.  Using a capacitor for ignition noise in the radios has been a standard for many, many years.  They take the ripple out of the alternator output which can and does transmit RF.  In a composite aircraft, this is a real issue, more so than in an aluminum skinned aircraft where the radios are basically shielded by the airframe.  



Barry is spot on with his discussion and I need to determine what size capacitor would be best.  Cessna uses a 5.72 microfarad capacitor in it's system.  And yes, the leads need to be very short to reduce the capacitor's resonance frequency.  We don't want it transmitting in the audio or Nav/Comm range.  I suppose using both a large and small capacitor would be best as Barry suggests.  



I assumed that since I have a Jabiru 3300 the ACU is a Jabiru unit and came with the engine.  I installed the engine, but the engine systems were installed by the dealer.  



Barry, are you speaking about installation on a Jabiru Engine or in general?  BTW, I am also an Electrical Engineer, but my design work was on integrated circuits in the 80's.

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Dennis

psm(at)att.net
Guest

Posted: Fri Apr 13, 2012 1:08 pm Post subject: Capacitor Installation for Ignition Noise

Dennis,



I've been about half following this discussion, and I too am a retired 

EE.  Let me make a few quick comments.



If you want to add a filter capacitor to the alternator I would be sure 

to keep it small.  If you put a large capacitor on an AC circuit it will 

load it down rather than providing the RF filtering you seek.  Large 

caps can be put on DC circuits like your 12V supply, but you probably 

don't need this.  The power supplies in quality radios like your SL-30 

will filter the input power quite nicely.



I think the key to getting rid of radio noise - especially when you have 

high quality equipment - is to make sure you have a very firm ground 

connecting all the electronics to the system ground point.  You also 

need to be sure you have properly shielded and grounded the audio cable 

from your headset to the radio.  This is usually isolated from the 

system ground.



Good luck,



Paul

Camas, WA



On 4/13/2012 1:43 PM, dwwilt wrote:

 	  Quote: 	
		   



 For a composite aircraft, I have fairly good grounds.  I have an Arion Lightning.  However, grounding is always an issue for composites.  Using a capacitor for ignition noise in the radios has been a standard for many, many years.  They take the ripple out of the alternator output which can and does transmit RF.  In a composite aircraft, this is a real issue, more so than in an aluminum skinned aircraft where the radios are basically shielded by the airframe.



 Barry is spot on with his discussion and I need to determine what size capacitor would be best.  Cessna uses a 5.72 microfarad capacitor in it's system.  And yes, the leads need to be very short to reduce the capacitor's resonance frequency.  We don't want it transmitting in the audio or Nav/Comm range.  I suppose using both a large and small capacitor would be best as Barry suggests.



 I assumed that since I have a Jabiru 3300 the ACU is a Jabiru unit and came with the engine.  I installed the engine, but the engine systems were installed by the dealer.



 Barry, are you speaking about installation on a Jabiru Engine or in general?  BTW, I am also an Electrical Engineer, but my design work was on integrated circuits in the 80's.



 --------

 Dennis





 Read this topic online here:



 http://forums.matronics.com/viewtopic.php?p=370729#370729

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