---------------------------------------------------------- JabiruEngine-List Digest Archive --- Total Messages Posted Fri 04/13/12: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:44 PM - Re: Capacitor Installation for Ignition Noise (dwwilt) 2. 02:08 PM - Re: Re: Capacitor Installation for Ignition Noise (Paul Mulwitz) ________________________________ Message 1 _____________________________________ Time: 01:44:14 PM PST US Subject: JabiruEngine-List: Re: Capacitor Installation for Ignition Noise From: "dwwilt" 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 ________________________________ Message 2 _____________________________________ Time: 02:08:03 PM PST US From: Paul Mulwitz Subject: Re: JabiruEngine-List: Re: 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: > --> JabiruEngine-List message posted by: "dwwilt" > > 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 > > ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message jabiruengine-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/JabiruEngine-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/jabiruengine-list Browse Digests http://www.matronics.com/digest/jabiruengine-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.