Field Observations of Personal Privacy Devices

J.C. Grabowski

Abstract:	Personal Privacy Devices (PPDs) are now recognized as being responsible for causing interference to GPS receivers. However, in November of 2009, when the Local Area Augmentation System (LAAS) Program installed its first Ground Based Augmentation System (GBAS) at Newark International Airport (EWR), this fact was not known. Within the first month of its installation, anomalies in GBAS processing were correlated to the presence of Radio Frequency Interference (RFI). Initial efforts to determine the source of this unexpected RFI were not successful. There was significant FAA interest in finding the source of this RFI and that interest resulted in the deployment of RFI detection and location equipment by a number of different groups. Zeta Associates temporarily installed equipment in early January 2010 that was capable of detecting and characterizing RFI but did not have emitter location capability. Characterization provided numerous clues as to the Radio Frequency (RF) bandwidth, modulation, the time duration of each RFI event, the time of day, and the day of the week when RFI events were observed. Unfortunately this characterization was not sufficient to determine the origins of the RFI. Additional groups using emitter location equipment traveled to EWR with the intent of identifying the location from which the RFI was transmitting. Those efforts from January through mid March of 2010 did not produce sufficiently reliable information to reduce the search area. Zeta Associates sent additional equipment, in March of 2010, with the explicit intent of reducing the search area. This additional equipment not only provided the first evidence that the source of the RFI was from PPDs, but has also provided significant characterization of their transmitted signals. The continuing interest in understanding PPD effects on GPS receivers has led to installation of remotely accessible monitoring equipment that continues to provide detailed characteristics of these devices. This paper describes the methodology that was used in successfully identifying these devices, and the determination that they are transmitting with low power and are in motion. This paper also provides detailed characteristics of observable parameters of the devices that have travelled near EWR and a number of Wide Area Augmentation System (WAAS) reference stations. Characteristics of observed PPD devices encompass a surprising wide variation in both externally observed RF spectra and also internal modulation. Detailed analysis provides an indication as to the quality of the manufacturing of these devices and also the local environment in which they are transmitting. Determining that an RFI transmitter is in motion is more certain if the RFI is observed simultaneously by multiple sensors. However, analysis from hundreds of RFI events indicates that when an RFI source is in motion, observations collected by a single sensor can provide sufficient information to determine that the RFI transmitter is in motion.
Published in:	Proceedings of the 2012 International Technical Meeting of The Institute of Navigation January 30 - 1, 2012 Marriott Newport Beach Hotel & Spa Newport Beach, CA
Pages:	689 - 741
Cite this article:	Grabowski, J.C., "Field Observations of Personal Privacy Devices," Proceedings of the 2012 International Technical Meeting of The Institute of Navigation, Newport Beach, CA, January 2012, pp. 689-741.
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