This is where we get into some compatibility issues as well as some of the FAA regulations for ADS-B. In short, yes, you can use one GPS antenna for multiple devices using an antenna splitter. However, there are a number of issues here. Some GPS antennae use coax. Some use a a 2 or 3 wire serial cable. Multiple devices may require antenna which may be incompatible with each other. A second issue is that most of our GPS units are WAAS. ADS-B requires a High Integrity WAAS GPS, which has a higher level of accuracy. Why the FAA decided 14 cm position accuracy was needed over 1.5M accuracy is fodder for another discussion. Never-the-less, the high integrity WAAS GPS is required, which has a different antenna that is likely not compatible with an older GPS or a standard WAAS GPS. Thus the multiple antenna mounted on several aircraft. Your ADS-B unit reports the accuracy integrity with every broadcast, so if you use the lower integrity antenna on your ADS-B unit, the FAA will be calling (Yes, I've got that call in the past), or more likely, they will disable reporting for your N number in their system and send you a notification of non-compliance. It's been my experience that the high integrity GPS antennae are the ones with 2 or 3 wire serial connections, but that is only an anecdotal observation from doing several installations, and I don't know that to be fact with all vendors.
Early on in the ADS-B implementation, the FAA regulations said the WAAS GPS was acceptable for ADS-B Out position reporting. Then they changed the regulation and decided all units had to be High Integrity WAAS and those that weren't were out of compliance and given a short time period to recall and fix all their existing ADS-B units. Some vendors recalled their units and installed new receivers in their ADS-B units. Does anyone remember NavWorx? NavWorx created a software patch for their units and changed the software to falsely report High Integrity GPS accuracy rather than replacing the GPS units and antenna. The FAA shut them down, then issued an A.D requiring the removal of all affected NavWorx units. -Jeff Scott Arkansas Ozarks > Sent: Friday, October 01, 2021 at 12:46 AM > From: "larry howell via KRnet" <[email protected]> > To: "larry howell via KRnet" <[email protected]> > Cc: "larry howell" <[email protected]> > Subject: KR>Re: New Transponder > > In my previous post I meant to say do any of you use one GPS antenna for > multiple pieces of electronics requiring a GPS signal. > > Larry H > > > On Oct 1, 2021, at 12:37 AM, larry howell via KRnet <[email protected]> > > wrote: > > > > When I saw this post from Luis it reminded me of something I learned at > > Oshkosh this year that I didn’t know. Some or all of you may know this but > > I did not. > > While I was talking to one of the aircraft spruce electronics expert I > > asked him about gps antennas. My question was geared towards adsb in and > > out gps antennas. Did it have to have its own gps antenna? He said no you > > only need one gps antenna for several pieces of equipment requiring a GPS > > signal. All you need is a multi splitter coming off the GPS antenna with > > separate cables going to each piece of equipment. I remember seeing > > airplanes that have two or three GPS antennas mounted on them so I just > > asked to see what answer I would receive. > > I’m wondering if any of you use one GPS for more than one piece of > > equipment and if it works as well as it should. > > While at Oshkosh I purchased the uAvionix echoUAT ADSB in and out package > > which includes the GPS antenna and some wiring for about $1300 or $1400 > > dollars. Jeff Scott told me he has this unit in his airplane and likes it. > > The electronic box is pretty small so will fit in a small place ________________________________ -Please see LIST RULES and KRnet info at http://www.krnet.org/info.html -Change list delivery options at https://list.krnet.org/list/krnet.list.krnet.org/ Affinity List Info Board -Search recent KRnet Archives at https://list.krnet.org/empathy/list/krnet.list.krnet.org/ -Search John Bouyea's decades of archive at https://www.mail-archive.com/[email protected]/
