Just before my 1st RV8 test flight at the start of a simple ground run all the GPS systems in my RV8 would not boot up (in total I think I have 5?). All the systems showed No GPS satellites and zero signal strength. To me this looked like a severe case of GPS Jamming (and it was)?? After some trouble shooting I found that when I turned off my GNS430W all the other GPS systems suddenly came back to life. I then swapped the GNS430 with one from another plane and same thing happened, all the GPS systems were dead?
Figuring an antenna cable or something went bad I did some testing and as best i could tell the antenna cable checked good, this only left the GA35 GPS antenna. I swapped a hockey puck $15 GPS antenna (I was using with my G5) with the GNS430W's GA35 antenna to the BNC connector on the 430 unit and it booted up normally and all the other GPS systems also. So my first RV8 test flights flew good using the $15 antenna on my 430. When I had my next chance I swapped the GA35 antenna with a GARMIN GA56 teardrop GPS ANTENNA (same hole pattern) using the same GA35 coax cable with a TNC to BNC adapter and again the 430 operated good.
In my GNS430W installation you can't just turn off your 430 NAV/GPS and leave the COM system operational, If I was on the road and experienced this problem and was able to trouble shoot as far as I did just swapping antennas would have been difficult since all my GPS systems use a different coax connector (TNC or SMA). So what would have been the fall back solution would be to just disconnect the GA35 antenna from the 430 (I didn't test this) to allow the Comm Radio to remain functional but not allow the 430 GPS to Jam all the other planes GPS receivers. I would think the VOR/ILS would also remain functional. The GA35 TSO'd GPS antenna currently sell for $309 on Aircraft Spruce. And yes they are the worse performing GPS antennas I have on either of my planes.
I have asked several avionics folks if they had ever seen a Garmin GPS antenna go this bad before and they all said No, so lesson learned is that GPS systems are far from being bullet proof and some of your most expensive trustworthy avionics can turn on you in surprising ways. So take this story as a documented worst case of what can go wrong with your TSO'd Garmin IFR rated GPS antenna and how it can affect all your GPS systems. I've not seen any Garmin published GPS failure mode that addresses this type of failure that will JAM all your GPS systems at once.
I'll let you know if Garmin wants this antenna back to analyze it and adds total GPS systems jamming as a possible GA35 failure mode?
Figuring an antenna cable or something went bad I did some testing and as best i could tell the antenna cable checked good, this only left the GA35 GPS antenna. I swapped a hockey puck $15 GPS antenna (I was using with my G5) with the GNS430W's GA35 antenna to the BNC connector on the 430 unit and it booted up normally and all the other GPS systems also. So my first RV8 test flights flew good using the $15 antenna on my 430. When I had my next chance I swapped the GA35 antenna with a GARMIN GA56 teardrop GPS ANTENNA (same hole pattern) using the same GA35 coax cable with a TNC to BNC adapter and again the 430 operated good.
In my GNS430W installation you can't just turn off your 430 NAV/GPS and leave the COM system operational, If I was on the road and experienced this problem and was able to trouble shoot as far as I did just swapping antennas would have been difficult since all my GPS systems use a different coax connector (TNC or SMA). So what would have been the fall back solution would be to just disconnect the GA35 antenna from the 430 (I didn't test this) to allow the Comm Radio to remain functional but not allow the 430 GPS to Jam all the other planes GPS receivers. I would think the VOR/ILS would also remain functional. The GA35 TSO'd GPS antenna currently sell for $309 on Aircraft Spruce. And yes they are the worse performing GPS antennas I have on either of my planes.
I have asked several avionics folks if they had ever seen a Garmin GPS antenna go this bad before and they all said No, so lesson learned is that GPS systems are far from being bullet proof and some of your most expensive trustworthy avionics can turn on you in surprising ways. So take this story as a documented worst case of what can go wrong with your TSO'd Garmin IFR rated GPS antenna and how it can affect all your GPS systems. I've not seen any Garmin published GPS failure mode that addresses this type of failure that will JAM all your GPS systems at once.
I'll let you know if Garmin wants this antenna back to analyze it and adds total GPS systems jamming as a possible GA35 failure mode?