---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Sat 05/03/08: 1 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:38 PM - Help with radio intereference (Andrew McMenamin) ________________________________ Message 1 _____________________________________ Time: 11:38:36 PM PST US From: "Andrew McMenamin" Subject: Avionics-List: Help with radio intereference I hope someone can help me! I have little technical knowledge and may have some of the technical terms incorrect but would appreciate any advice. I fly a Skyranger with a Simonini engine, at a controlled airfield. The Simonini is an Italian two cylinder, two stroke liquid cooled engine with dual Ducati ignition; two plugs per cylinder. It performs best at over 5000 rpm. I have significant problems with noise on the radio. I have a microair radio and a DRE 4000 headset. The radio is beautifully clear on the ground with the engine not running. After start up, I get an RPM - related interference which makes the radio very hard to hear over 5000 rpm - i.e. at cruise. I am also told the Tower find it hard to hear me. I can overcome it by reducing RPM to 4000 before transmitting but this is not desirable!. The interference reduces noticeably as I cut each magneto in turn at the full power ground run up (when listening to the ATIS). This makes me think it is ignition related. The spark plugs are NGK resistor plugs. The plug caps are standard, no resistor and non-shielded. The HT cables are NGK "racing" - i.e. copper core, no apparent shielding. The radio is positioned beside the two magneto switches on the dash, and shielded by the aluminium firewall from the mags. It is not shielded from the mag switch wires. I suspect the problem is to do with the HT cables, or the plug caps, or possibly the wires to the mag switches. I have read that I should not use resistor caps when already using resistor plugs. Should I use different HT leads?? Andrew ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message avionics-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/Avionics-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/avionics-list Browse Digests http://www.matronics.com/digest/avionics-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.