---------------------------------------------------------- Avionics-List Digest Archive --- Total Messages Posted Sun 12/10/06: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 01:45 PM - Garmin GNS430 Nav board repaired twice (=?ISO-8859-1?Q?Andr=E9_Beusch?=) 2. 09:56 PM - Re: Garmin GNS430 Nav board repaired twice (John Rippengal) ________________________________ Message 1 _____________________________________ Time: 01:45:56 PM PST US From: =?ISO-8859-1?Q?Andr=E9_Beusch?= Subject: Avionics-List: Garmin GNS430 Nav board repaired twice I have a Garmin GNS430 in my Glasair Super II. The comm is connected to a dipole antenna in the vertical stabilizer, the nav is connected directly (no splitter) to the dipole antenna in the horizontal stabilizer. Both are the antennas that were provided by Stoddard Hamilton, the kit manufacturer, and were installed as per the instruction manual. The antennas perform well. Both times, the VOR/LOC lost 30 dB of sensitivity, apparently the input stage was destroyed. The first repair cost me about $1000, the second was warranty. I wonder if someone had this problem with any kind of nav receiver. Garmin said that it could have been overloaded by the comm transmission because the antennas are to close to each other. (they don't say anything about this in the installation manual) Many people use a splitter for NAV/glideslope, so their receiver gets less signal and would perhaps not be exposed to this problem. As an electronics engineer, I'd like to understand this and will make a measurement of the power that actually gets in the Nav receiver. I have a 250 MHz oscilloscope for that. This nav receiver should pass RTCA DO-196, if someone has these documents handy, I'd be interested to see what the damage input power should be. I also consider putting a 6dB attenuator or an RF limitter on the Nav antenna input. Any opinions? Thanks, --Andre Beusch ________________________________ Message 2 _____________________________________ Time: 09:56:52 PM PST US From: "John Rippengal" Subject: Re: Avionics-List: Garmin GNS430 Nav board repaired twice Bite the bullet Andre and change the position of the Nav antenna. John From: "Andr Beusch" > > I have a Garmin GNS430 in my Glasair Super II. > The comm is connected to a dipole antenna in the vertical stabilizer, the > nav is connected directly (no splitter) to the dipole antenna in the > horizontal stabilizer. > Both are the antennas that were provided by Stoddard Hamilton, the kit > manufacturer, and were installed as per the instruction manual. The > antennas perform well. Both times, the VOR/LOC lost 30 dB of sensitivity, > apparently the input stage was destroyed. > The first repair cost me about $1000, the second was warranty. > I wonder if someone had this problem with any kind of nav receiver. > Garmin said that it could have been overloaded by the comm transmission > because the antennas are to close to each other. > (they don't say anything about this in the installation manual) > Many people use a splitter for NAV/glideslope, so their receiver gets > less signal and would perhaps not be exposed to this problem. > As an electronics engineer, I'd like to understand this and will make a > measurement of the power that actually gets in the Nav receiver. I have a > 250 MHz oscilloscope for that. > This nav receiver should pass RTCA DO-196, if someone has these documents > handy, I'd be interested to see what the damage input power should be. > I also consider putting a 6dB attenuator or an RF limitter on the Nav > antenna input. > > Any opinions? > > > Thanks, --Andre Beusch ------------------------------------------------------------------------------------- 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.