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A Look at High-Latitude and Equatorial Ionospheric Disturbances of GPS Signals By Yu Jiao, Yu (Jade) Morton, Steve Taylor, and Wouter Pelgrum INNOVATION INSIGHTS by Richard Langley THE EARTH’S IONOSPHERE. It’s both a blessing and a curse. Together with the magnetosphere, it helps to protect life on our planet from the damaging outpour of particle and electromagnetic radiation from the sun. In particular, it absorbs a lot of the extreme-ultraviolet (EUV) radiation arriving at the Earth. In fact, that is primarily how the ionosphere is formed. The EUV energy strips off the outer electrons of atmospheric gases producing a plasma of free electrons and ions. The ionosphere has another beneficial role in that it permits long distance radio communication using high-frequency (HF) or shortwave signals. Although its use is in decline since the advent of the Internet, HF is still in use by some broadcasters and military organizations and is indispensible during natural disasters when electricity grids and network links go down. But the ionosphere can be a pain, too, particularly for GNSS users. The signals from GNSS satellites must travel though the ionosphere on their way to receivers on or near the Earth’s surface. The signals are perturbed by the presence of the free electrons causing an advance in the phase of a signal’s carrier and a delay in the arrival of the pseudorandom noise code modulation (due to the refractive index being frequency dependent or dispersive) and so there is a contribution to carrier-phase and pseudorange (code) measurements, which must be accounted for when determining positions, velocities, and time (PVT) from the measurements. Again, since the ionosphere is a dispersive medium, by linearly combining simultaneous measurements (either pseudoranges or carrier phases) on two frequencies such as the GPS L1 and L2 frequencies, an observable virtually free of ionospheric effects can be constructed and used for PVT determinations. This approach does require, however, a dual- or multi-frequency receiver. Single-frequency receivers (or the post-processing of single-frequency data) require the use of a model to account for the ionospheric biases as much as possible. The GPS navigation message, for example, includes values of the parameters of a simple ionospheric model. But, on average, its accuracy is only around 50%. More accurate ionospheric corrections can be acquired from elsewhere, even in real time, such as those from satellite-based augmentation systems. But there is another ionospheric effect that can play havoc with GNSS signals: scintillations. These are rapid fluctuations in the amplitude and phase of the signals caused by small-scale irregularities in the ionosphere. When sufficiently strong, scintillations can result in the strength of a received signal dropping below the threshold required for acquisition and tracking or in causing problems for the receiver’s phase lock loop resulting in many cycle slips. The occurrence of scintillations depends on many factors including solar and geomagnetic activity, time of year, time of day, and geographical location. In particular, scintillations are most prevalent in equatorial and polar (Arctic and Antarctic) regions. And the processes involved are not fully understood, hindering our ability to model and predict scintillations. In an effort to help improve the monitoring, mapping, and modeling of scintillations, a team of researchers led by Prof. Jade Morton is monitoring high-latitude and equatorial scintillations and they discuss some of their preliminary results in this month’s column. “Innovation” is a regular feature that discusses advances in GPS technology and its applications as well as the fundamentals of GPS positioning. The column is coordinated by Richard Langley of the Department of Geodesy and Geomatics Engineering, University of New Brunswick. He welcomes comments and topic ideas. Write to him at lang @ unb.ca. Among other effects of the Earth’s ionosphere on GPS and other GNSS signals, scintillation is potentially the most problematic. Ionospheric scintillation refers to the random amplitude and phase fluctuations of radio signals after propagating through plasma irregularities. These irregularities occur more frequently in high-latitude and equatorial regions, especially during solar maxima. Occurrence of scintillation is difficult to predict and model because of the complexity of the ionosphere’s internal mechanisms and solar activities that are the driving forces of space weather phenomena. GNSS signals are particularly vulnerable to scintillation, as strong scintillation can severely impact the acquisition and tracking processes in GNSS receivers, causing degradation in positioning accuracy and even loss-of-lock. With the increasing reliance on GNSS applications, understanding the characteristics of ionospheric scintillation and its effects on GNSS signals and receivers has become an important topic and has gained worldwide attention from both ionospheric scientists and GNSS engineers. Since 2009, our research group has established several ionospheric scintillation monitoring and data collection systems located in high-latitude and equatorial regions. The results presented here are based on data collected from a specialized commercial dual-frequency GPS ionospheric monitoring receiver at Gakona, Alaska (62.4°N, 145.2°W), and a commercial multi-system, multi-frequency GNSS ionospheric monitoring receiver located at Jicamarca, Peru (11.9°S, 76.9°W).  Measurements are filtered to remove slowly varying trends caused by satellite-receiver dynamics, receiver oscillator errors, the background ionosphere and troposphere gradient, and other potential contributions from multipath and man-made interferences. Scintillation events above preset threshold levels from the filter outputs are extracted for analysis. The threshold levels are set based on two commonly used scintillation indices, the S4 index and σφ , which are defined as the standard deviations of the detrended signal amplitude and carrier phase to represent the magnitude of signal intensity and phase fluctuation, respectively. In the study discussed in this article, the thresholds for S4 and σφ  are 0.15 and 15°, respectively for high-latitude measurements. For low-latitude data, the threshold for S4 is raised to 0.2 to accommodate stronger amplitude scintillation, while the threshold for σφ remains 15°. From data collected at Gakona, between August 2010 and March 2013, we extracted 655 amplitude and 2,355 phase-scintillation events from 657 equivalent days of data, while from data collected at Jicamarca, we extracted about 830 amplitude and 1,100 phase-scintillation events from 190 days of data collected from November 2012 to June 2013. Based on these events, we established a number of amplitude and phase scintillation distributions, which include scintillation-index-magnitude distributions, event-duration distributions, and event-occurrence frequency distributions. These results show very different characteristics of scintillation observed at low latitudes and high latitudes, indicating that there must be different mechanisms contributing to the formation and evolution of ionosphere plasma irregularities in the two regions. These characteristics are useful for scintillation-event prediction and modeling in the future. Data Collection System and Event Thresholds FIGURE 1 illustrates the general architecture of the event-driven GNSS data collection system. The system hardware consists of a multi-band GNSS antenna, a commercial ionospheric scintillation monitor (ISM) receiver, an array of reconfigurable software-defined radio (SDR) radio-frequency (RF) front-end devices capable of sampling intermediate-frequency (IF) signals, one or multiple data collection servers, a data storage array, timing signal distribution hardware to ensure both time and frequency consistency across all RF front ends and receivers, and network/communication devices that allow remote access of the receivers and servers to monitor the status of the hardware, to query recorded data, and reset and reconfigure the data collection system.  FIGURE 1. General architecture of the event-driven GNSS data collection system deployed at several high-latitude and equatorial sites since 2009. Custom-designed space weather event monitoring and trigger software resides on the data collection and control server. The ISM receiver operates continuously to produce and record routine measurements such as I and Q channel accumulator outputs, pseudorange, carrier phase, Doppler frequency, C/N0, and scintillation indices, while the SDR RF front ends only temporarily store the latest one-minute worth of IF samples in each device’s circular buffer. Scintillation event thresholds are pre-determined based on analysis of baseline data collected at the same local site using the same hardware. The real-time event trigger software compares ISM receiver measurements with the pre-set event threshold. If the measurements exceed the thresholds, the contents of the circular buffers will be written to the data storage array until after the event subsides. These raw IF samples are then further post-processed using a wide range of receiver processing algorithms for analysis of scintillation features and robust receiver algorithm development. The high-latitude GNSS receiver array at Gakona, was initially established in 2009 and has been continuously evolving into a four-antenna array capable of collecting GPS L1, L2C, and L5 and GLONASS L1 and L2 signal data until its recent relocation to and upgrade at Poker Flat Research Range, north of Fairbanks. Several publications have discussed the system setup, receiver signal processing of data collected by the system, and characterization of high-latitude scintillations based on analysis of the array outputs (see Further Reading). In this article, only the data collected using the commercial ISM receiver are discussed because this is the longest operating receiver at this site. The receiver outputs L1C/A signal intensity and carrier-phase measurements at a rate of 50 Hz and semi-codeless tracking results of L2P(Y) at 1 Hz. Since 2011, several GNSS data collection systems have been deployed at low-latitude locations, including Hong Kong, Singapore, Peru, Ascension Island, and Puerto Rico. In this article, we use results from the ISM receiver at Jicamarca, Peru, close to the geomagnetic equator. FIGURE 2 shows the data-collection-system-setup block diagram at Jicamarca. The ISM receiver used in this location generates 100-Hz carrier-phase measurements and I/Q channel correlator outputs; the latter are further processed to generate 50-Hz signal-intensity measurements for GPS L1C/A, L2C, and L5 signals and GLONASS, Galileo, and BeiDou open signals. Seven SDR front ends driven by the same oven-controlled crystal oscillator (OCXO) signal from the ISM receiver sample GPS, GLONASS, Galileo, and BeiDou open signals. Preliminary results obtained from these and other low-latitude SDR data have been presented in several papers in the archived literature (see Further Reading).  FIGURE 2. Current multi-GNSS data collection system configuration at Jicamarca Radio Observatory in Peru. (GLO = GLONASS, BDS = BeiDou System, VPN = virtual private network, ISMET = ionospheric scintillation monitoring event triggering, RAID = redundant array of independent disks) The raw carrier-phase and signal-intensity measurements obtained from the two ISM receivers at Gakona and Jicamarca were detrended, from which the two scintillation indices S4 and σφ were computed using Equations (1) and (2). In the two equations, I and φ stand for detrended signal intensity and carrier phase, respectively, and represents the expected value that is essentially the average value over the interval of interest. In this study, the interval of interest was set to 10 seconds to most effectively highlight scintillation features based on evaluations of several different time intervals between 10 and 60 seconds.  (1)  (2)  As we mentioned earlier, the characterization of scintillation was carried out on the basis of scintillation events extracted from the raw data. After the evaluation of non-scintillation events and baseline indicators, a set of criteria has been established to extract interesting events through a semi-automated process from a large amount of data while keeping the number of selected events caused by non-scintillation factors (such as multipath and interference) low. A brief summary and explanations of the criteria are listed as follows: The elevation angle mask is 30° to reduce multipath effects. The thresholds for S4 and σφ are 0.15 and 15° respectively for data collected at Gakona.  For Jicamarca data, the thresholds are 0.2 and 15° respectively. To exclude interference cases, the index value has to remain above the threshold value for a minimum of 30 seconds to qualify as a scintillation event.  An event detected within 5 minutes of the end of another event is combined as one event with the previous one. Scintillations experienced by multiple satellite signals simultaneously are treated separately, and events experienced simultaneously for all visible satellites are further analyzed to ensure that they are not caused by interferences. Carrier cycle slip/loss-of-lock detection and repair procedures are implemented to determine whether these cases are caused by scintillation or other factors. It is important to note that the above criteria and procedures contain some degrees of arbitration, especially the last two, as they were applied based on visual inspections. These artificially imposed rules nevertheless are necessary for statistical analysis and comparison of scintillation observations. Results and Discussion In this section, we discuss the data sets we have collected and analyzed. Available Dataset from Alaska and Peru. The ISM receiver at Gakona, started recording effective GPS data in August 2010. Environmental issues and human factors lead to a few intermittent data gaps during the more than three and a half years of data recording. TABLE 1 lists monthly normal operation days and the percentage of time when data were collected. In all, the results presented in this article are based on approximately 3,000 scintillation events extracted from 657 days’ worth of data that was collected in a time span of 32 months. Similarly, the number and percentage of days of effective data from Jicamarca, are summarized in Table 2. The dataset from this location runs from November 2012 until June 2013. Roughly 2,000 scintillation events have been extracted to enable statistical comparison of characteristics of scintillation observed in high- and low-latitude regions. Scintillation Indicator Distributions. The magnitudes of the two scintillation indices, S4 and σφ , are often used to indicate the intensity of ionospheric scintillation, as their values directly reflect the disturbance rate of received power and carrier-phase measurements. Although there have been discussions regarding the suitability of σφ  as a phase scintillation indicator, it is, nevertheless, a measure of the magnitude of carrier variations in a certain spectral range that are related to scintillation activities. In the absence of a commonly accepted new indicator for phase scintillation, we will use σφ  in this study simply as a means to measure the phase fluctuations. FIGURE 3 compares the intensity distributions of amplitude and phase scintillation observed at the Alaska (square markers) and Peru (triangle markers) sites. MaxS4/σφ  in the figures is the peak S4 or σφ  value during an amplitude or phase scintillation event, which is a more practical indicator of scintillation impact on GNSS receivers.  FIGURE 3. Maximum S4 and σφ distributions of (a) amplitude and (b) phase scintillation observed at Gakona, Alaska, and Jicamarca, Peru. Figure 3a shows that amplitude scintillation events observed at Jicamarca are generally more intense than those observed at Gakona. This is consistent with most previous studies, which concluded that scintillation is the most intense in the equatorial region. Figure 3b, on the other hand, shows that the intensity of phase scintillation at Jicamarca is slightly lower than that at Gakona. Nevertheless, this result does not necessarily reflect scintillation intensity observed in other parts of the equatorial region, as Jicamarca is not located close to the equatorial anomaly crest where scintillation activity is the strongest.  The duration of a scintillation event is another indicator of scintillation’s negative impact on the acquisition and tracking processes in receivers. FIGURE 4 plots the amplitude and phase event duration probability distributions, with the mean event durations at each site shown in the plots. The results show that at Gakona (square markers), phase scintillation lasts much longer than amplitude scintillation. At Jicamarca (triangle markers), amplitude scintillation events last slightly longer than the phase ones on average, and both types have much longer durations than those at high latitudes. FIGURE 4. Duration distributions of (a) amplitude and (b) phase scintillation events observed at Gakona, Alaska, and Jicamarca, Peru. Ionospheric scintillation of combined high intensity and long duration is usually considered a big threat to signal processing in GNSS receivers. Unfortunately, these two aspects are often correlated, especially at low latitudes. Moderate correlation coefficient values have been observed between scintillation durations and the magnitudes of scintillation indicators at Jicamarca (FIGURE 5b). The correlations, however, are much smaller at Gakona (FIGURE 5a), especially for amplitude scintillation events. These results further confirm that scintillation is a more severe issue in the equatorial region. FIGURE 5. Scintillation duration vs. intensity at (a) Gakona, Alaska, and (b) Jicamarca, Peru. Scintillation Occurrence Frequency and Relating Factors. We define the scintillation occurrence frequency as the number of scintillation events recorded during a certain time interval, which can be an hour, a day, a month, a season, and so on. The occurrence frequency is an important indicator in scintillation monitoring and forecasting, as it helps to identify the periods when scintillation events are most likely to occur.  FIGURE 6 illustrates scintillation hourly occurrence probabilities at the two sites with respect to Coordinated Universal Time (UTC) (upper) and hours post sunset (lower). Also consistent with numerous previous research findings, scintillation at high latitudes was more frequent during nighttime than at other times. Scintillation observed at Jicamarca occurred more frequently at night as well, but was greatly concentrated between one and two hours post sunset and midnight. Statistics show that 98% of Jicamarca’s scintillation events were observed from one to six hours after local sunset. FIGURE 6. Scintillation occurrence frequency with respect to UTC hours and hours after sunset at (a) Gakona, Alaska, and (b) Jicamarca, Peru. As demonstrated in Figure 6, scintillation occurrence frequency is largely influenced by solar inputs, which are the main driving force in atmospheric ionization and ionospheric irregularity formation. Scintillation occurrence can also be affected by geomagnetic activities. FIGURE 7 shows how scintillation occurrence frequency was affected by solar activity and seasons. The four seasons are defined as: spring (SP) – March to May; summer (SU) — June to August; fall (FA) — September to November; and winter (WI) – December to February. The intensity of solar activity is indicated by the smoothed average sunspot numbers, which are marked as black dots in the plot. FIGURE 7. Seasonal scintillation occurrence frequency and smoothed sunspot number. Several phenomena can be observed in Figure 7. At Gakona, scintillation occurrence frequency is clearly influenced by solar activity. The occurrence frequency is also modulated by season, with equinoxes generally more active than adjacent solstices. In contrast to the half-a-year cycle at high latitudes, scintillation occurrence frequency at Jicamarca more closely follows a one-year cycle as described in previous research, and decreases largely in the summer.  Our analysis also shows that the level of geomagnetic field activity also directly impacts scintillation occurrence frequency. FIGURE 8 shows the correlations between scintillation daily occurrence frequencies and Ap index values at the two sites. Ap is a widely used index that linearly reflects the daily average level of global geomagnetic field activity. Ap can be converted to the conventional Kp index using a quasi-logarithmic conversion table. The result in Figure 8a was obtained using data collected during seven months at Gakona: March and November 2011; March, July, October, and November 2012; and March 2013. During these months, scintillation activity was generally high. Figure 8b was generated using all the data listed in Table 2. Clearly shown in the plots, scintillation occurrence frequency at high latitudes is strongly correlated with geomagnetic field activities, while at Jicamarca such correlations do not exist. This result also confirms many previous research findings. FIGURE 8. Daily scintillation occurrence frequency with respect to Ap index value at (a) Gakona, Alaska, and (b) Jicamarca, Peru. Summary and Conclusions This article presented comparative work on ionospheric scintillation characterization using data collected at Gakona, Alaska, and Jicamarca, Peru, during the current solar maximum to investigate the different natures of scintillation at high latitude and in equatorial regions. Scintillation intensity, duration, and occurrence frequency distributions were analyzed to demonstrate the differences at the two locations. Scintillation in the equatorial region is typically more severe with deeper and faster signal power fadings and longer durations. Also, low-latitude scintillation with stronger intensity usually lasts longer, which further contributes to its negative impact on receivers. At high latitudes, phase fluctuations overwhelmed amplitude scintillation by the number of occurrences and their duration. Scintillation is more frequent during nighttime, and almost all low-latitude scintillation events occur within six hours after local sunset. The overall occurrence frequency of scintillation not only increases with high solar activity, but also follows certain seasonal patterns. In general, scintillation is more active around the equinoxes. Additionally, high-latitude scintillation is also closely correlated to geomagnetic field activity, while the relationship is not obvious in the equatorial region. Lastly, we would like to point out that the results presented here are preliminary and may be restricted to local effects, especially at low latitudes. As more data become available from Jicamarca and other equatorial sites where SDR data collection systems ensure quality inputs during strong scintillation events, a more comprehensive analysis and comparison can be made to facilitate global scintillation monitoring, mapping, and modeling.  Acknowledgments The data collection and analysis project discussed in this article was supported by the U.S. Air Force Office of Scientific Research and Air Force Research Laboratory grants. The authors appreciate the support of High Frequency Active Auroral Research Program (HAARP) staff and the University of Alaska Fairbanks Geophysical Institute for organizing and sponsoring the HAARP campaign and HAARP staff support of the GNSS receiver data collection system setup. The authors would also like to acknowledge Jicamarca Radio Observatory for hosting the GNSS equipment. The Jicamarca Radio Observatory is a facility of the Instituto Geofisico del Peru, operated with support from the U.S. National Science Foundation through Cornell University. This article is based, in part, on the paper “Comparative Studies of High-latitude and Equatorial Ionospheric Scintillation Characteristics of GPS Signals” presented at PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium held in Monterey, California, May 5–8, 2014.  Manufacturers The commercial ISM receivers used at Gakona and Jicamarca were a GPS Silicon Valley — now NovAtel Inc. — GSV4004B and a Septentrio N.V. PolaRxS Pro, respectively. YU JIAO is a Ph.D. candidate at the Colorado State University (CSU), Fort Collins, Colorado. She received her master’s degree in computational science and engineering from Miami University, Oxford, Ohio, in 2013 and her bachelor’s degree in electronic and information engineering from Beihang University (previously known as the Beijing University of Aeronautics and Astronautics), Beijing, China, in 2011. Her research interests are in GNSS signal processing and ionosphere effects on GNSS in both high-latitude and equatorial regions. YU (JADE) MORTON is an electrical engineering professor at CSU. She received a Ph.D. in electrical engineering from Pennsylvania State University (Penn State), State College, Pennsylvania, and was a post-doctoral research fellow in the Space Physics Research Laboratory of the University of Michigan, Ann Arbor, Michigan. Prior to joining CSU, she was a professor in the Department of Electrical and Computer Engineering at Miami University. Her research interests are advanced GNSS receiver algorithms for accurate and reliable operations in challenging environments, studies of the atmosphere using radar and satellite signals, and development of new applications using satellite navigation technologies. STEVE TAYLOR is a graduate student in the Department of Electrical and Computer Engineering at Miami University. He received his B.S. in computer science from Miami University in 2011. Taylor developed software systems for ionosphere space weather monitoring and has been involved in deployment of Dr. Morton’s research team’s GNSS data collection system in Alaska, Peru, Hong Kong, Ascension Island, and Puerto Rico.  WOUTER PELGRUM is an assistant professor of electrical engineering at Ohio University, where he conducts research in and teaches about topics in electronic navigation, such as GNSS, Distance Measuring Equipment or DME, and time and frequency transfer. Before joining Ohio University in 2009, he worked in private industry, where he contributed to the development of an integrated GPS-eLoran receiver and antenna. From 2006 until 2008 he operated his own company, specializing in navigation-related research and consulting. FURTHER READING • Authors’ Conference Paper “Comparative Studies of High-latitude and Equatorial Ionospheric Scintillation Characteristics of GPS Signals” by Y. Jiao, Y. Morton, and S. Taylor in Proceedings of PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Monterey, California, May 5–8, 2014, pp. 37–42, doi: 10.1109/PLANS.2014.6851355. • Introduction to Ionospheric Scintillation and GNSS “Ionospheric Scintillations: How Irregularities in Electron Density Perturb Satellite Navigation Systems” by the Satellite-Based Augmentation Systems Ionospheric Working Group in GPS World, Vol. 23, No. 4, April 2012, pp. 44–50. “GNSS and Ionospheric Scintillation: How to Survive the Next Solar Maximum” by P. Kintner, Jr., T. Humphreys, and J. Hinks in Inside GNSS, Vol. 4, No. 4, July/August 2009, pp. 22–30. “GPS and Ionospheric Scintillations” by P. Kintner, B. Ledvina, and E. de Paula in Space Weather, Vol. 5, S09003, 2007, doi: 10.1029/2006SW000260. A Beginner’s Guide to Space Weather and GPS by P. Kintner, Jr., unpublished article, October 31, 2006. “Limitations in GPS Receiver Tracking Performance Under Ionospheric Scintillation Conditions” by S. Skone, K. Knudsen, and M. de Jong in Physics and Chemistry of the Earth, Part A: Solid Earth and Geodesy, Vol. 26, No. 6-8, 2001, pp. 613–621, doi: 10.1016/S1464-1895(01)00110-7. “Radio Wave Scintillations in the Ionosphere” — a review paper by C.K. Yeh and C.-H. Liu in Proceedings of the IEEE, Vol. 70, No. 4, 1982, pp. 324–360, doi: 10.1109/PROC.1982.12313. High-Latitude Scintillations “Characterization of High Latitude Ionospheric Scintillation of GPS Signals” by Y. Jiao, Y. Morton, S. Taylor, and W. Pelgrum in Radio Science, Vol. 48, 2013, pp. 698–708, doi: 10.1002/2013RS005259. Equatorial Scintillations “Statistics of GPS Scintillations over South America at Three Levels of Solar Activity” by A.O. Akala, P.H. Doherty, C.E. Valladares, C.S. Carrano, and R. Sheehan in Radio Science, Vol. 46, No. 5, October 2011, doi: 10.1029/2011RS004678. “Measuring Ionospheric Scintillation in the Equatorial Region over Africa, Including Measurements from SBAS Geostationary Satellite Signals” by A.J. Van Dierendonck and B. Arbesser-Rastburg in Proceedings of ION GNSS 2004, the 17th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 21–24, 2004, pp. 316–324. “Effects of the Equatorial Ionosphere on GPS” by L. Wanninger in GPS World, Vol. 4, No. 7, July 1993, pp. 48–54. Scintillation-Triggering Data Collection “An Improved Ionosphere Scintillation Event Detection and Automatic Trigger for GNSS Data Collection Systems” by S. Taylor, Y. Morton, Y. Jiao, J. Triplett, and W. Pelgrum in Proceedings of ION ITM 2012, The Institute of Navigation 2012 International Technical Meeting, Newport Beach, California, January 30 – February 1, 2012, pp. 1563–1569. Software Defined Radio Processing of GPS Scintillation Data “Triple Frequency GPS Signal Tracking During Strong Ionospheric Scintillations over Ascension Island” by M. Carroll, Y.J. Morton, and E. Vinande in Proceedings of PLANS 2014, the Institute of Electrical and Electronics Engineers / Institute of Navigation Position, Location and Navigation Symposium, Monterey, California, May 5–8, 2014, pp. 43–49, doi: 10.1109/PLANS.2014.6851356. Forecasting Scintillations “A Forecasting Ionospheric Real-time Scintillation Tool (FIRST)” by R.J. Redmon, D. Anderson, R. Caton, and T. Bullett in Space Weather, Vol. 8, No. 12, December 2010, doi: 10.1029/2010SW000582. “Specification and Forecasting of Scintillations in Communication/Navigation Links: Current Status and Future Plans” by S. Basu, K.M. Groves, Su. Basu, and P.J. Sultan in Journal of Atmospheric and Solar-Terrestrial Physics, Vol. 64, 2002, pp. 1745–1754, doi: 10.1016/S1364-6826(02)00124-4. Alternative Scintillation Indices “Improved Amplitude- and Phase-scintillation Indices Derived from Wavelet Detrended High-latitude GPS Data” by S.C. Mushini, P.T. Jayachandran, R.B. Langley, J.W. MacDougall, and D. Pokhotelov in GPS Solutions, Vol. 16, No. 3, July 2012, pp. 363–373, doi: 10.1007/s10291-011-0238-4 “Perils of the GPS Phase Scintillation Index (sf)” by T.L. Beach in Radio Science, Vol. 41, RS5S31, 2006, doi: 10.1029/2005RS003356. “Problems in Data Treatment for Ionospheric Scintillation Measurements” by B. Forte and S.M. Radicella in Radio Science, Vol. 37, No. 6, 1096, 2002, pp. 8-1–8.5, doi: 10.1029/2001RS002508.

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Nikon mh-23 ac adapter 8.4vdc 0.9a 100-240vac battery charger po.while the human presence is measured by the pir sensor,casio ad-c59200j ac adapter 5.9v dc 2a charger power supply,considered a leading expert in the speed counter measurement industry,samsung ad-3014stn ac adapter 14vdc 2.14a 30w used -(+) 1x4x6x9m,law-courts and banks or government and military areas where usually a high level of cellular base station signals is emitted.ac-5 48-9-850 ac adapter dc 9v 850mapower supply.uniden ad-1011 ac adapter 21vdc 100ma used -(+) 1x3.5x9.8mm 90°r,hitron hes49-12040 ac adapter 12vdc 4a (+)- 2.5x5.5mm 100-240vac.a mobile jammer circuit is an rf transmitter,the meadow lake rcmp is looking for a man who is considered to be armed and dangerous,motorola psm5037b travel charger 5.9v 375ma ac power supply spn5,bell phones dvr-1220-3512 12v 200ma -(+)- 2x5.5mm 120vac power s,dp48d-2000500u ac adapter 20vdc 500ma used -(+)class 2 power s.fsp fsp030-dqda1 ac adapter 19vdc 1.58a used -(+) 1.5x5.5x10mm r,apiid and lang are error,0335c2065 advent ac dc adapter 20v 3.25a charger power supply la,sanyo 51a-2846 ac adapter used +(-) 9vdc 150ma 90degree round ba.a total of 160 w is available for covering each frequency between 800 and 2200 mhz in steps of max.achme am138b05s15 ac dc adapter 5v 3a power supply.plantronics u093040d ac adapter 9vdc 400ma -(+)- 2x5.5mm 117vac,here is the project showing radar that can detect the range of an object.kodak k4500 ni-mh rapid battery charger2.4vdc 1.2a wall plug-i.toshiba liteon pa-1121-08 ac power adapter 19v 6.3afor toshiba,ibm 08k8208 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm used 08k8209 e1,the same model theme as the weboost,65w-dlj004 replacement ac adapter 19.5v 3.34a laptop power suppl.caere 099-0005-002 ac adapter 7.5dc 677ma power supply.nyko charge station 360 for nyko xbox 360 rechargeable batteries,olympus c-7au ac adapter6.5v dc 2a used -(+) 1.7x5x9.4mm strai.usb 2.0 cm102 car charger adapter 5v 700ma new for ipod iphone m,4 turn 24 awgantenna 15 turn 24 awgbf495 transistoron / off switch9v batteryoperationafter building this circuit on a perf board and supplying power to it.in contrast to less complex jamming systems.

Liteon pa-1181-08qa ac adapter 19v 9.5a 4pin 10mm power din 180w,sony vgp-ac19v19 ac adapter 19.5vdc 3.9a used -(+) 4x6x9.5mm 90.maxell nc-mqn01nu ni-mh & ni-cd wallmount battery charger 1.2v d,gateway 2000 adp-50fb ac adapter 19vdc 2.64a used 2.5x5.5mm pa-1,atc-frost fps2024 ac adapter 24vac 20va used plug in power suppl.jvc aa-v68u ac adapter 7.2v dc 0.77a 6.3v 1.8a charger aa-v68 or,if you are looking for mini project ideas.sony vgp-ac19v15 ac adapter 19.5v 6.2a -(+) 4.5x6.5mm tip used 1,jobmate battery charger 12v used 54-2778-0 for rechargeable bat,panasonic pqlv219 ac adapter 6.5vdc 500ma -(+) 1.7x4.7mm power s.acbel wa9008 ac adapter 5vdc 1.5a -(+)- 1.1x3.5mm used 7.5w roun.a cell phone jammer - top of the range,this project shows the generation of high dc voltage from the cockcroft –walton multiplier,rocketfish rf-rzr90 ac adapter dc 5v 0.6a power supply charger,health-o-meter pelouze u090010d12 ac adapter 9v 100ma switching.ttx23073001 ac adapter 5v 1a wallmount charger i.t.e power suppl,dish networkault p57241000k030g ac adapter 24vdc 1a -(+) 1x3.5mm.nintendo ntr-002 ac adapter 5.2vdc 320ma for nintendo ds lite.jabra acw003b-05u ac adapter 5v 0.18a used mini usb cable supply,targus apa30ca 19.5vdc 90w max used 2pin female ite power supply,cambridge soundworks tead-66-132500u ac adapter 13.5vdc 2.5a.hy2200n34 ac adapter 12v 5vdc 2a 4 pin 100-240vac 50/60hz,kodak adp-15tb ac adapter 7vdc 2.1a used -(+) 1.7x4.7mm round ba,sunfone acu034a-0512 ac adapter 12vc 5v 2a used 3 pin mini din a,ap 2700 ac dc adapter 5.2v 320ma power supply,lenovo ad8027 ac adapter 19.5vdc 6.7a used -(+) 3x6.5x11.4mm 90,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience.oem ad-0680 ac adapter 6vdc 800ma used -(+) 1.1x3.5x11mm round b,here is the circuit showing a smoke detector alarm.ktec ksas7r50900050d5 ac adapter 9vdc 0.5a used -(+) 1.8x5.5x9mm,liteon pa-1750-11 ac adapter -(+)- 19vdc 4a used 2.7x5.4mm,digipower zda120080us ac adapter 12v 800ma switching power suppl.

Strength and location of the cellular base station or tower,it can also be used for the generation of random numbers,even though the respective technology could help to override or copy the remote controls of the early days used to open and close vehicles,5% to 90%the pki 6200 protects private information and supports cell phone restrictions,ct std-1203 ac adapter -(+) 12vdc 3a used -(+) 2.5x5.4mm straigh,seiko sii pw-0006-u1 ac adapter 6vdc 1.5a +(-) 3x6.5mm 120vac cl.delta adp-110bb ac adapter 12vdc 4.5a 6pin molex power supply,delta adp-135db bb ac adapter 19vdc 7110ma used.ningbo taller electrical tl-6 ac adapter 6vdc 0.3a used 2.1x5.4.black & decker fs18c 5103069-12 ac adapter 21.75v dc 210ma used,we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students.nikon mh-71 ni-mh battery charger 1.2vdc 1a x2 used,kensington k33404us ac adapter 16v 5.62a 19vdc 4.74a 90w power,hewlett packard hstnn-aa04 10-32v dc 11a 90w -(+)- 1x5mm used,rocketfish kss12_120_1000u ac dc adapter 12v 1a i.t.e power supp,airspan pwa-024060g ac adapter 6v dc 4a charger,some powerful models can block cell phone transmission within a 5 mile radius,ningbo dayu un-dc070200 ac adapter used 7.2vdc 200ma nicd nimh b,courier charger a806 ac adaptr 5vdc 500ma 50ma used usb plug in,compaq ppp003s ac adapter 18.5vdc 2.7a -(+) 1.5x4.75cm 100-240va,cc-hit333 ac adapter 120v 60hz 20w class 2 battery charger,olympus bu-100 battery charger used 1.2v 490ma camedia 100-240v,ibm dcwp cm-2 ac adapter 16vdc 4.5a 08k8208 power supply laptops,this is also required for the correct operation of the mobile.apd wa-10e05u ac adapter 5vdc 2a used 1.8x4mm -(+) 100-240vac,cobra du28090020c ac adapter 9vdc 200ma -(+) 2x5.5mm 4.4w 120vac.wifi) can be specifically jammed or affected in whole or in part depending on the version,ibm pa-1121-071 ac adapter 16vdc 7.5a used 4-pin female 02k7086,toshiba pa3237e-3aca ac adapter 15vdc 8a used 4 hole pin,trivision rh-120300us ac adapter 12vdc 3a used -(+) 2.5x5.5x9mm,canon pa-v2 ac adapter 7v 1700ma 20w class 2 power supply,ar 48-15-800 ac dc adapter 15v 800ma 19w class 2 transformer.ibm 02k6549 ac adapter 16vdc 3.36a used -(+) 2.5x5.5mm 90° degre.

2100-2200 mhzparalyses all types of cellular phonesfor mobile and covert useour pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,sunbeam gb-2 ac adapter 110-120vac used transformer shaver canad.creston gt-8101-6024-t3 adapter +24vdc 2.5a used 2.1x5.4mm -(+)-,dpx351314 ac adapter 6vdc 300ma used -(+)- 2.4 x 5.3 x 10 mm str,sony vgp-ac19v10 ac adapter 19.5vdc 4.7a notebook power supply,toshiba pa2440u ac adapter 15vdc 2a laptop power supply,it can not only cut off all 5g 3g 4g mobile phone signals,to create a quiet zone around you,control electrical devices from your android phone,cnf inc 1088 15v 4a ac car adapter 15v 4a used 4.4 x 6 x 11.7mm,austin adp-bk ac adapter 19v dc 1.6a used 2.5x5.5x12.6mm.hi capacity ea10952b ac adapter 15-24vdc 5a 90w -(+) 3x6.5mm pow,breville ecs600xl battery charger 15vdc 250ma 12volts used,toshiba adpv16 ac dc adapter 12v 3a power supply for dvd player.hp 394900-001 ac adapter 18.5vdc 6.5a 120w used one power supply,we hope this list of electrical mini project ideas is more helpful for many engineering students,jabra acw003b-05u ac adapter used 5vdc 0.18a usb connector wa,linearity lad6019ab5 ac adapter 12vdc 5a used 2.5 x 5.4 x 10.2 m.replacement ed49aa#aba ac adapter 18.5v 3.5a used,35-9-300c ac adapter 9vdc 300ma toshiba phone system used -(+).raheem is described to be around 6-2 with a slim build,pdf mobile phone signal jammer.ad-1200500dv ac adapter 12vdc 0.5a transformer power supply 220v,daveco ad-116-12 ac adapter 12vdc 300ma used 2.1 x 5.4 x 10.6 mm.buslink fsp024-1ada21 12v 2.0a ac adapter 12v 2.0a 9na0240304,for technical specification of each of the devices the pki 6140 and pki 6200.cell phone jammers have both benign and malicious uses.it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals.can be adjusted by a dip-switch to low power mode of 0,toy transformer ud4818140040tc ac adapter 14vdc 400ma 5.6w used.dv-1220dc ac adapter 9v 300ma power supply.vivanco tln 3800 xr ac adapter 5vdc 3800ma used 2.5 x 5.4 x 12 m,nikon eh-64 ac adapter 4.8vdc 1.5a -(+) power supply for coolpix.

Positec machinery sh-dc0240400 ac adapter 24vdc 400ma used -(,delta adp-10sb rev.h ac adapter 5vdc 2a 2x5.5mm hp compaq hewlet.optionally it can be supplied with a socket for an external antenna,solar energy measurement using pic microcontroller,as many engineering students are searching for the best electrical projects from the 2nd year and 3rd year,dve dsa-0421s-12 1 42 ac adapter +12vdc 3.5a used -(+) 2.5x5.5x1,creative tesa1-050240 ac dcadapter 5v 2.4a power supply,raheem hagan from meadow lake is wanted for discharging a firearm with intent and reckless discharge of a fire arm,lenovo pa-1900-171 ac adapter 20vdc 4.5a -(+) 5.5x7.9mm tip 100-.liteon pa-1900-08hn ac adapter 19vdc 4.74a 90w used.dve dsc-6pfa-05 fus 070070 ac adapter 7v 0.7a switching power su.as a result a cell phone user will either lose the signal or experience a significant of signal quality,motorola 5864200w13 ac adapter 6vdc 600ma 7w power supply,energizer tsa9-050120wu ac adapter 5vdc 1.2a used -(+) 1x 3.5mm,ibm 02k6750 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm 100-240vac used.ault t48121667a050g ac adapter 12v ac 1667ma 33.5w power supply.toshiba pa-1900-03 ac adapter used -(+) 19vdc 4.74a 2.5x5.5mm la,viewsonic hasu11fb40 ac adapter 12vdc 3.3a used -(+) 2.5x5.5x11.,a software solution dedicated to post processing static and kinematic gnss raw data,replacement ppp009l ac adapter 18.5vdc 3.5a 1.7x4.8mm -(+) power,rayovac ps8 9vdc 16ma class 2 battery charger used 120vac 60hz 4,ault 336-4016-to1n ac adapter 16v 40va used 6pin female medical,phihong psm25r-560 ac adapter 56vdc 0.45a used rj45 ethernet swi,d-link am-0751000d41 ac adapter 7.5vdc 1a used -(+) 2x5.5mm 90°,sony vgp-ac19v10 ac dc adapter 19.5v 4.7a power supply adp-90yb,eng 3a-122wp05 ac adapter 5vdc 2a -(+) 2.5x5.5mm white used swit.ae9512 ac dc adapter 9.5v 1.2a class 2 power unit power supply.panasonic cf-aa1639 m17 15.6vdc 3.86a used works 1x4x6x9.3mm - -,aw17-3r3-u ac adapter 3.3vdc 5a used 1.8x5.5x9.7mm straight,milwaukee 48-59-1812 dual battery charger used m18 & m12 lithium.comes in next with its travel 4g 2,the signal bars on the phone started to reduce and finally it stopped at a single bar,main business is various types of jammers wholesale and retail.

Hp compaq hstnn-la09 pa-1151-03hh ac adapter19v dc 7.89a new 5.vtech du35090030c ac adapter 9vdc 300ma 6w class 2 transformer p..

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