Testing GPS Antennas

I did a search and didn't find anything that appeared directly applicable. I am servicing mobile location reporting devices, a component of which is a power injection board feeding active antennas. This is nothing unusual, however I want or need to develop a reliable way to compare antennas and determine whether a particular antenna installation has problems, or if the problem arises elsewhere.

I read another thread discussing the inability of using a spectrum analyzer in this pursuit due to the GPS signal being so far below the noise. For individual dis-connectable components, I could use a VNA to measure loss/gain, however essentially there are only two components (ignoring interconnects): the antenna with built-in LNA and coax and the power injection circuit.

Can anyone provide a relatively inexpensive system for doing these measurements to create a pass/fail system to rule out the antenna system as a problem?

I was about to pull the trigger on a relatively inexpensive spectrum analyser, which *could* indicate if there were strong signals near the GPS frequency (cellular in particular) interfering, but that apparently (for the purposes of this discussion) would be its' only use.

Thanks!

 

Wouldn't it be possible to use a GPS receiver that outputs NMEA sentences and a simple program like VisualGPS to display signal levels? If you want pass/fail, you could write a simple BASIC program to read the applicable NMEA sentences, parse them and just print pass or fail after a few minutes of collecting signal strength data. Or am I totally misunderstanding your needs?