I am in need of testing a GPS antenna and cable assembly after installation at a reasonable cost.
I have a GPS antenna installed on an airplane, then the coax cable from the antenna goes down to the receiver. The system is already assembled and validated technically and in production, but we find that after some shipments around the country something goes wrong in the cable assembly.
We are testing out a complete system inside of a metal hanger so there is no available sky view for real satellite reception. Besides we are trying to control the test and provide a go/no-go simple automated test.
We really want to know that we have not pinched the coax cable and confirm that all the connections are still good from outside the antenna through the aircraft and all the way down the cable. I am thinking it should not be necessary to pass a GPS capture and location measurements. I am thinking that I can find a simple method to transmit an RF signal in the GPS range and then receive it on the other end of the cable to confirm the antenna and all the connections and the cable are still good.
I am thinking that I could attach an instrument on the receive end of the coax cable to detect what is transmitted from a non-contact transmitting antenna held a few inches above the GPS antenna.
Any ideas out there? Any simple equipment that does this already that can be connected to a Windows or Linux PC to initiate the test and read back the response signal if not to say go or no-go?
—– edit of March 25 —–
At this point, I believe the best way to go on this test effort is to provide a signal generator driving an antenna, then provide a receiver / detector at the "bottom" end. Now I need to find hopefully a single PCIe card that will give me an L-Band range signal generator and a receiver with an API to control and read from s/w. I think the SDR version is more complex than it needs to be but that still may work. And since the quantities of those are high, that may get those prices down to a good range anyway.
Any ideas out there? I am looking at Pentek, Agilent, NI and any others that may be appropriate. I haven't yet figured out what to call it to do my search for what I need, other than a Signal Generator and Receiver.
Best Answer
A TDR (Time Domain Reflectometer) would seem to be the answer here - we used these in the Navy to ring out long RF cable runs/transmission lines. It will tell you if there are any shorts or opens (and where they are) and whether the end is terminated in a proper load (antenna connected).
Its a relatively pricy piece of equipment at about $1500-$2000, but its a huge labor saver.