Verifying Performance Improvements of an Existing GNSS Antenna Signal Distribution, Using SkyView

Validating signal quality improvements on a GNSS antenna distribution system, after replacing a passive splitter with an active one. Justifying a relatively inexpensive upgrade for big improvement.

Case 2 - Verifying Improved Performance of an Existing GNSS Antenna Distribution

2.1 What We Started With

We used the SkyView^™ GNSS antenna verification tool to qualify an existing roof antenna installation and distribution system. The antenna was a multi-band quad-constellation, which is a good starting point. However, the relatively short antenna feed (30.5m / 100ft) was all passive, with a 1x2 passive splitter to feed two receivers. Although the initial 72-hour results showed a decent performance, based on the color scale, it also shows plenty of room for improvements.

Original performance of roof antenna with a passive 1x2 splitter.

Signal Quality (C/No) Color Scale:

45 to 52+ dB-Hz, Excellent
36 to 44 dB-Hz, Good
27 to 35 dB-Hz, Fair
18 to 26 dB-Hz, Marginal
9 to 17 dB-Hz, Poor
1 to 8 dB-Hz, Bad

2.2 Improvements

After replacing the 1x2 passive splitter with an active 1x4 splitter, with 10 dB total gain to compensate for the split loss and some cable loss, the overall signal quality improvements are significant, as seen on the second SkyView map results.

Improved performance of roof antenna after installing an active 1x4 splitter, with 10dB total gain.

The new GNSS signal distribution system not only offers better signal quality, stability and resiliency to the receivers/devices connected to it, it also provides two extra ports for new equipment. VeEX's SkyView GNSS reception coverage maps helped validate and document the improvements, as well as justify (bring into perspective) the small investment on the new 1x4 active splitter.

2.3 General Recommendations

Do not use T connectors as RF splitters.
Always terminate unused ports on active and passive GNSS splitters.
Procure good quality active GNSS splitters with enough gain to compensate for the power split and cable losses. Make sure they are multiband and supports all the relevant constellations and bands.

We do recommend testing for 72 hours, to log more data and obtain better coverage, since the SkyView test runs unattended anyway. However, if time is not on your side, one can use a dual-band quad-constellation receiver to run tests for 24 hours, with decent coverage since there are a lot more satellite signals to log (assuming that the antenna under test is also multiband). In single or dual constellation receiver scenarios, 24 hours may not provide enough datapoints for a meaningful coverage map.