Generally speaking, there should be no issues when using a good quality active GNSS splitter, as long as it covers all the satellite systems and bands supported by the GNSS receiver card installed in the test set. However, here are a few things to keep in mind.
Passive Splitters
Generally, passive splitters are not recommended. However, if that is the only option, we suggest using GNSS-specific splitters with proper impedances, bandwidth and no more than 1:2 ratio. Whether it would work well or not will depend on the active antenna's gain as well as main cable feed's length and attenuation. Also make sure that the antenna is still properly powered.
Should you choose to use the passive splitter approach, it is advisable to refer to the test set's GNSS Signal Quality (C/No density) table to confirm the detection of all expected satellite systems, the relevant frequency bands, and, most critically, that the C/No of the satellites directly overhead meet or exceeds 36 dB-Hz.
Refer to the following article to better understand the GNSS Signal Quality levels, according to VeEX's GNSS receivers.
Active GNSS Splitters
Active GNSS-specific splitters are the preferred solution for sharing a single roof antenna among multiple GNSS receivers, including those from VeEX. However, several critical considerations must be taken into account:
- The active splitter must be specifically designed for GNSS application and has the bandwidths to cover all the satellite systems and bands supported all the receivers connected to it.
- Active splitters require power. If it doesn't come with a dedicated DC power supply, it is most likely powered by one of the receivers through one of the ports. So, check the splitter and antenna power consumption, to make sure one of the GNSS receivers can provide enough voltage and current capacity to power both. (e.g., the optional GNSS receiver in VeEX's portable test sets are typically rated to 5V and <60 mA, which may not be enough to power both, the splitter and antenna). A dedicated power supply is recommended, so the system doesn't get powered down by accident (e.g., the GNSS receiver providing the power may auto reboot during a software update)
- The splitter's internal LNA gain must be (at least) enough to cover the loss induced by the 1:N signal split. Ideally, it should offer some extra gain to compensate for the antenna cable feed's loss.
- For Precision Timing applications, it is recommended to source active splitters from trusted brands, which state the internal delay in their specifications. This value shall be added to the GNSS antenna cable delay compensation settings, to keep the 1PPS as accurate as possible.
- The splitter won't allow you to directly measure the antenna cable delay, so you have to measure the segments (main antenna feed and distribution drops) independently using a cable delay meter, such as the TDR-based CX41, then add the splitter delay to calculate total cable delay for each distribution branch.
- Always terminate unused ports in the splitter.