Splitting GPS can be done, but practically you might not want to
Hi Nitty,
I know you said disregard ... however, dealing with GPS is my day job. You can easily split the signal from a good quality GPS antenna and feed multiple receivers. We do this regularly at the office, splitting one active antenna to 8+ receivers with no practical effect on receiver performance. The noise figure of the system is set to a very high degree by the first amplifier in the system, which is the low noise amplifier integrated into the antenna.
To split the signal, you will need to provide power to the antenna, usually through a special "bias tee" upstream of the splitter; normally, the GPS receiver provides this itself for a direct connection to the antenna, but many splitters don't pass this bias voltage through. And then, you need the splitter to send the signal to the various radios.
All together, you are talking a price tag of at least -- if not more -- of what a separate additional antenna will cost. This fact, plus the added complexity of the setup, and the potential signal point failure of a single GPS antenna, argues strongly for the installation of an additional antenna. Easy, simple, and likely cheaper. If you had 8 GPS receivers in the plane, that might be a different story, but for two, use two antennas. That's my $0.02.