Frequently Asked Questions
Questions frequently asked about all aspects of a GPS Repeater System.
Ideally the antenna should go at or near roof level to provide an uninterrupted view of the whole sky.
To obtain an accurate posistional fix most GPS devices need to receive signals from at least four satellites.
It may be that the only place available to install the antenna is on the side of a building, which means that there is line of sight to only half of the sky.
Before going to the lengths of installing an antenna and feeder cable (and possibly finding out that the antenna location is not suitable after all) there is a simple test you can do with a standard satellite navigation device such as a TomTom:
- Switch it on and stand out in the open, as close to the intended antenna location as possible.
- When the satnav device has acquired enough satellites to get a positional fix, tap the main screen to gain access to the screen behind it.
- It will tell you how many satellites it is receiving at that location.
The GPS satellite signals are picked up by an outdoor antenna, preferably mounted at height and in free space so as to “see” as much of the sky as possible. The received signals travel down a low-loss coaxial cable to a repeater unit inside the building or area that needs the coverage.
The repeater amplifies the signal and re-radiates it inside the building so that GPS devices in that space can lock on to the Global Positioning System as if they are outside.
Any GPS devices within the coverage area will be “locked on” to the GPS signal; hence when the device is taken outside the building it doesn’t take any time at all to acquire the signal and obtain a location fix.
This is particularly useful for GPS systems in emergency vehicles that would otherwise incur delays when leaving the covered area.
In a commercial situation, such as a laboratory where GPS-enable equipment is manufactured, tested, repaired or serviced, there is no need to take it outside the building in order to receive a live signal.
Any number of GPS-enabled devices can receive the signal from a repeater unit, so only one outdoor antenna and feeder cable would be needed per system, as opposed to a tangled mess of multiple antennas and cables in a workshop.
The repeater unit runs off a 12V DC supply, via an AC/DC adapter similar in size to a mobile phone charger.
This is the only part of the system that requires a mains power supply; however the GPS antenna has an built-in Low Nose Amplifier (LNA) that receives a 5V DC power supply from the repeater via the coaxial feeder cable.
Additionally, the Splitter, Amplifier and Amplifier/Splitter units derive their power supply from the 5V DC emitted by the repeater.
Absolutely – you can use a splitter unit (with an amplifier if needed) to feed the incoming GPS signal to multiple indoor repeater units.
This approach is generally outside the scope of a standard GPS Repeater Kit and would be classed as a custom-designed system – either way just get in touch with FalTech GPS and ask for advice, it won’t cost you to talk to us!
Depending on the actual distance from the outdoor antenna to the space where the signal is required, there are a number of options – contact FalTech to ask advice on the best approach for your situation.
You could use low-loss coaxial cable with GPS line amplifiers, or if the distance is too great for that we would specify some fibre-optic equipment that can effectively extend the length of the feeder cable up to several kilometres if needed.
Yes – SBAS stands for satellite-based augmentation system; it is a system that supports wide-area or regional augmentation through the use of additional messages broadcast by satellites.
Typically the information comes from multiple ground stations located at accurately-surveyed points, and is sent to one or more satellites for broadcast to end users. Sometimes referred to as WADGPS (wide-area DGPS).
These signals pass straight through the GPS repeater system to the interior where needed – contact FalTech for further information.
