Is it possible to passively pipe GPS satellite signals indoors via a waveguide, or 2 antennas connected by a coax? If so, with what type of waveguide, antennas, coax, etc. should I try and experiment? Thanks.
We've done this for a development project that involved GPS reception. We just wanted to be able to get a GPS signal indoors at our engineering office, for basic development of the GPS drivers.
We put a good quality GPS antenna on the roof, with coax going down into the office below. On the ceiling of the office, the coax connected to a GPS-band RF amplifier, which output through an antenna also on the ceiling.
It was a low power amplifier, so it only radiated an effective signal over a short distance within the office space--less than 10 metres. But that was enough to serve our purposes.
The other equipment we used sometimes was a GPS simulator, which simulated a bunch of satellites, and could convince a GPS unit that it was at any location of our choosing. It radiated through an antenna, again, at low signal levels so it disrupted only a small area. And we only used it indoors, within our offices.
You could use a large antenna on the roof, pipe the data through an RF channel and then radiate it into the building with another antenna.
If you place an antenna on the roof and pipe signals into the building and then receive them in the building, you are effectively making the point you are receiving at the antenna upstairs. Once they hit this point they are piped in series into the building.
The noise will be a problem, each antenna will lose power and the cabling with have loss. I would suggest an RF amplifier connect at the antenna end on the roof, if not, one inside will still give an improvement. This will make getting a lock much easier (if you do have problems).
I would suggest coax cable, running a waveguide is not very feasible. A waveguide will be easier to pipe the signal in with, but will make your power amplifier hard.
Your antenna on the roof needs to have a wide receive angle. This will take some research, you will probably want a high effective area to receive as much power as possible.
Inside you will want an antenna that is very directed at the location you want your device for the best receive. I would suggest a horn antenna.
I did this quickly, I will spend more time on it later if I can, I think this gives a general idea. Getting this to work will not be easy. Please let me know if there is something specific I can add to help.
We provide equipment that will bring the GPS signal indoors. Yes, you need a passive antenna and an active antenna - you have to be able to calculate the correct amount of cable and possibly the use of an amplifier. All of this is regulated by the FCC. Unless you are a Federal agency, part of the military or using this in an anechoic chamber, you have to apply for a license from the FCC.
This seems like a lot of work, for very little gain, to me. You would have to subtract the lengths of each of the waveguides from the distances calculated by the GPS receiver electronics. In fact it's more complicated than that: the signal would reflect around inside the wave guide, making the apparent length longer than the actual length.
My suggestion: put the receiver on the roof, in a weather-proof housing, and then send the coordinates wherever you need them, wired or wirelessly.
Edit: I think I didn't understand the point of the OPs question. I thought he was interested in putting GPS in a moving vehicle like an RV. If Ian's assumption is correct and OPs goal is to test a GPS from indoors, then my suggestion won't really work either. I think the only solution possible would be to use a piece of coax with an external antenna. But make sure the coax is just the right length for the frequencies used - GPS signals are very weak and any line losses would certainly cause problems.
Note: I think the other answers for this are better than mine. Just wanted to throw this out there, especially if you use an active device.
This is effectively building a GPS repeater. To my knowledge, at least in the US, there are regulations as to when/where you can use one.
It can be done, there are devices to do it if you look around (how else would people design devices that use GPS if they had to be outside all the time???), but you need to meet regulatory standards and the rules so as to not interfere with others.