Melbourne Keilor Park – Major L1 Jamming Event 9 Dec 2024 at 8:37am
Since mid 2024, the Keilor Park GRIFFIN Sensor at Melbourne airport’s southern business precinct (refer earlier), has routinely tracked vehicle L1 jamming privacy devices, weekly driving on the surrounding freeways. Mostly, the RFI levels are relatively minor, which wouldn’t cause much disruption beyond 100m. However, on Monday, 9 December at 8:37am a very powerful L1 wideband jammer was observed and tracked regionally for 80secs.
The recorded event starts on Keilor Park Drive (KPD) with the L1-RFI vehicle heading south at 400m range with it’s signal 10m below the GRIFFIN phased antenna array horizon. GRIFFIN’s automatic tracking beam locks the southbound RFI vehicle. For 10secs, it’s slower moving as it approaches the southern KPD traffic lights, (refer left blue sky-polar plot multiple 3D bearings at 165deg). At this point, GRIFFIN phased antennas have a much clearer Line-Of-Sight (LOS) to the vehicle, but, the vehicle is still below the antenna array horizon so reception is diminished.
As traffic clears, the RFI vehicle continues south across the freeway overpass, and then takes the Calder Hwy on-ramp to head NW at speed. The GRIFFIN Sensor continues to track the RFI Vehicle NW for several kms. Interestingly, as the RFI Vehicle’s height increased while emerging from the Maribyrnong River valley to the west, the received RFI signal becomes much stronger as the LOS is elevated above the antenna array’s horizon plain, even though the distance is rapidly increasing.
For 80secs, this was a very significant L1 jamming event, which clearly disrupted the NovAtel OEM7 GNSS survey Receiver co-located with the GRIFFIN sensor, (refer top right L1 C/No red line chart). Certainly, any aircraft on GBAS vertical guidance finals to MEL airport, approaching runways 34 or 60 during this interference event would have most certainly been adversely affected. With just one additional GRIFFIN Sensor installed regionally, this RFI Vehicle would have easily been accurately 2D geolocated continuously.
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