Originally Posted by Bavafa
Just wondering if anyone has shared the same GPS antenna from a G3X with G5 successfully. I was thinking of using a splitter to extend the GPS antenna to the G5 instead of yet another antenna so it can work all independently which is it sole purpose to be my back up instrument.
I highly doubt that the internal antenna in the G5 will receive any signal considering that it has lots of metal above it.
We don't recommend GPS antenna splitters, but you have lots of options to consider for the G5.
First and best is to enable the internal WAAS GPS receiver and have an external antenna (glareshield or top of aircraft) connected to the G5. This gives you the most independence and provides the best performance when everything else is unavailable or load shed in a power emergency.
If you want to see how well your internal antenna, glareshield, or externally mounted antenna is working with your G5, you can pull your aircraft outside and use the GPS Configuration page in config mode to tell you if your installation is adequate. Note that this test is only for those using the G5 internal WAAS GPS receiver
The G5 has a very sensitive WAAS GPS receiver, and will almost always have enough signal to receive a 3D or 3D Differential fix to be able to determine and display the basic track and ground speed information, but having the high quality signal necessary for the G5 to use GPS data to improve the attitude measurement is something quite different.
Here is an example of a poor installation that would still provide the basic GPS data on the display.
The G5 can operate without a GPS (see below), but for the best performance, you want to have a 3D or 3D Differential fix with a green check mark shown next to the fix type. If you do not see this green check mark on this page, your installation needs improvement.
You can also disable the internal GPS receiver on the G5 and rely on GPS data provided by the G3X/G3X Touch system (over the CAN bus), or the connected WAAS GNS/GTN using MapMX over RS-232. These are not quite as good as the external antenna since you are reliant on one of these data sources being available at all times for the best performance.
Also keep in mind that in the worst case scenario when the G5 has no GPS data of any kind to use, it falls back to degraded mode operation using air data to correct for attitude sensor drift.
When we fly the 2+ hours of degraded mode flight tests to satisfy DO-334 TSO requirements, we disable the internal G5 GPS receiver, and shut down any external MapMX data being provided by GTX/GNS/GTN and also disable G3X provided GPS data. The DO-334 maneuvers are designed to challenge an ADAHRS while it is using an alternate means of aiding (in this case air data).
Whew, long answer to a simple question.