Originally Posted by rv7charlie
And there are dozens of other serial output GPS modules that will do the same thing, often for <$20.
When I built my RV-7, I used one of these cheap GPS receivers as a second GPS input. One day I was flying along and all of my GPS's failed - I wasn't receiving any GPS serial data on the cheap GPS receiver, and my Garmin 430W was reporting it couldn't lock onto any satellites, along with my iPad mini couldn't get a valid GPS position.
It turns out my cheap GPS failed in a way that it jammed all of the other GPS receivers on my airplane. Since I didn't have a switched power source to that GPS, I couldn't shut it off.
I decided to spend the good money for a Garmin 18X OEM LVC receiver. It has worked flawlessly since I installed it in 2013. I'm not trying to say the Garmin 18x doesn't have the potential of failing the same way the cheap GPS receiver did, but my money is on the Garmin GPS receiver definitely being higher quality and less likely.