Possible-yes... Practical?
It is possible to use one GPS antenna for two receivers, but a simple BNC TEE won't do the trick. The problem is that GPS antennas contain small amplifiers that get their power from DC supplied by the receiver over the coax. So you have DC going one way and RF going the other. If you connect two receivers together the DC supplies could fight each other and damage one or both receivers.
The cheap and dirty way around this is to use a DC block to isolate one receiver from the TEE connection. According to froogle, DC blocks start at about $25. Of course, the non-isolated receiver must be operational for either receiver to get a signal in this case.
Having said that, I'd never use this method in a critical application (such as IFR.) To properly split the signal requires a power divider. A simple TEE won't equally divide the power between the two devices. But, if you use a power divider, the DC generally won't pass through. There are commercial devices out there that can accomplish the task in a critical application, but I suspect their prices are probably more than you would pay for a 2nd antenna that could be hidden under the cowl or canopy.
Two antennas also provide a measure of redundancy.
Paige
RV-8A (finish kit)
