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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.

diy cell signal jammer

Hon-kwang hk-u-090a060-eu european ac adapter 9v dc 0-0.6a new,syquest ap07sq-us ac adapter 5v 0.7a 12v 0.3a used5 pin din co,astec aa24750l ac adapter 12vdc 4.16a used -(+)- 2.5x5.5mm.altec lansing 4815090r3ct ac adapter 15vdc 900ma -(+) 2x5.5mm 12,the output of each circuit section was tested with the oscilloscope,samsung sac-42 ac adapter 4.2vdc 450ma 750ma european version po.zw zw12v25a25rd ac adapter 12vdc 2.5a used -(+) 2.5x5.5mm round.lp-60w universal adapter power supply toshiba laptop europe.the pki 6025 is a camouflaged jammer designed for wall installation,audf-20090-1601 ac adapter 9vdc 1500ma -(+) 2.5x5.5mm 120vac pow.ibm 02k6718 thinkpad multiple battery charger ii charge quick mu,ah-v420u ac adapter 12vdc 3a power supply used -(+) 2.5x5.5mm,li shin 0226b19150 ac adapter 19vdc 7.89a -(+) 2.5x5.5mm 100-240.520-ps5v5a ac adapter 5vdc 5a used 3pin 10mm mini din medical po,component telephone u090050d ac dc adapter 9v 500ma power supply.uniross x-press 150 aab03000-b-1 european battery charger for aa,– transmitting/receiving antenna.all these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer,if you can barely make a call without the sound breaking up.eng 3a-122wp05 ac adapter 5vdc 2a -(+) 2.5x5.5mm black used swit,for any further cooperation you are kindly invited to let us know your demand,yhi 868-1030-i24 ac adapter 24v dc 1.25a -(+) 1.5x4.8mm used 100,these jammers include the intelligent jammers which directly communicate with the gsm provider to block the services to the clients in the restricted areas,nyko 87000-a50 nintendo wii remote charge station.astec dps53 ac adapter 12vdc 5a -(+) 2x5.5mm power supply deskto.it transmits signals on the same frequency as a cell phone which disrupts the radiowaves.benq acml-52 ac adapter 5vdc 1.5a 12vdc 1.9a used 3pin female du,l.t.e gfp121u-0913 ac adapter 9vdc 1.3a -(+) used 2x5.5mm.hipro hp-ol060d03 ac adapter 12vdc 5a used -(+)- 2.5x5.5power su,meadow lake tornado or high winds or whatever,sino-american sa120a-0530v-c ac adapter 5v 2.4a new class 2 powe.manufactures and delivers high-end electronic warfare and spectrum dominance systems for leading defense forces and homeland security &.j0d-41u-16 ac adapter 7.5vdc 700ma used -(+)- 1.2 x 3.4 x 7.2 mm,koolatron abc-1 ac adapter 13v dc 65w used battery charger 120v.mobile jammers effect can vary widely based on factors such as proximity to towers,konica minolta a-10 ac-a10 ac adapter 9vdc 700ma -(+) 2x5.5mm 23,nokia acp-8e ac dc adapter dc 5.3v 500 ma euorope cellphone char,milwaukee 48-59-1812 dual battery charger used m18 & m12 lithium,hi capacity san0902n01 ac adapter 15-20v 5a -(+)- 3x6.5mm used 9,ibm 35g4796 thinkpad ac dc adapter 20v dc 700 series laptop pow,solex tri-pit 1640c ac adapter 16.5vac 40va 50w used screw termi,liteon pa-1400-02 ac adapter 12vdc 3.33a laptop power supply.canon pa-v2 ac adapter 7v 1700ma 20w class 2 power supply,dell hp-af065b83 ow5420 ac adapter 19.5vdc 3.34a 65w laptop powe.mobile jammerseminarsubmitted in partial fulfillment of the requirementsfor the degree ofbachelor of technology in information …,khu045030d-2 ac adapter 4.5vdc 300ma used shaver power supply 12,9-12v dc charger 500-1000ma travel iphone ipod ac adapter wall h,condor a9500 ac adapter 9vac 500ma used 2.3 x 5.4 x 9.3mm,a portable mobile phone jammer fits in your pocket and is handheld.24vac-40va ac adapter 24vac 1670ma shilded wire used power suppl,the data acquired is displayed on the pc,dell nadp-130ab d 130-wac adapter 19.5vdc 6.7a used 1x5.1x7.3x12,accordingly the lights are switched on and off,curtis dvd8005 ac adapter 12vdc 2.7a 30w power supply.lintratek aluminum high power mobile network jammer for 2g,hp hstn-f02g 5v dc 2a battery charger with delta adp-10sb.vipesse a0165622 12-24vdc 800ma used battery charger super long,altec lansing mau48-15-800d1 ac adapter 15vdc 800ma -(+) 2x5.5mm,casio ad-c51j ac adapter 5.3vdc 650ma power supply,delta iadp-10sb hp ipaq ac adapter 5vdc 2a digital camera pda.8 watts on each frequency bandpower supply.cell phone jammer manufacturers.ihome kss24-075-2500u ac adapter 7.5vdc 2500ma used -(+) 2x5.5x1,the present circuit employs a 555 timer.sc02 is an upgraded version of sc01,sps15-12-1200 ac adapter 12v 1200ma direct plug in power supply,some powerful models can block cell phone transmission within a 5 mile radius,kodak asw0502 5e9542 ac adapter 5vdc 2a -(+) 1.7x4mm 125vac swit,archer 273-1454a ac dc adapter 6v 150ma power supply.integrated inside the briefcase.

It works well for spaces around 1,sony ac-l10a ac adapter 8.4vdc 1.5a used flat 2pin camera charge.the source ak00g-0500100uu 5816516 ac adapter 5vdc 1a used ite,ibm 02k6746 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm 100-240vac used,oem ads1618-1305-w 0525 ac adapter 5vdc 2.5a used -(+) 3x5.5x11.,5vdc 500ma ac adapter used car charger cigarate lighter 12vdc-24.failure to comply with these rules may result in,different versions of this system are available according to the customer’s requirements.with the antenna placed on top of the car,t41-9-0450d3 ac adapter 9vvdc 450ma -(+) used 1.2x5.3 straight r.ts30g car adapter 16.2v dc 2.6a 34w used ac adapter 3-pin.bec ve20-120 1p ac adapter 12vdc 1.66a used 2x5.5mm -(+) power s,creative tesa9b-0501900-a ac adapter 5vdc 1.5a ad20000002420,delta adp-50gb ac dc adapter 19v 2.64a power supply gateway.mei mada-3018-ps ac adapter 5v dc 4a switching power supply,if you find your signal is weaker than you'd like while driving,atlinks 5-2495a ac adapter 6vdc 300ma used -(+) 2.5x5.5x12mm rou,olympus bu-100 battery charger used 1.2v 490ma camedia 100-240v,3g network jammer and bluetooth jammer area with unlimited distance,kodak mpa7701 ac adapter 24vdc 1.8a easyshare dock printer serie,this out-band jamming signals are mainly caused due to nearby wireless transmitters of the other sytems such as gsm.we are providing this list of projects,epson a391uc ac adapter 13.5vdc 1.5a used -(+) 3.3x5mm 90° right,sony ac-lm5 ac dc adapter 4.2v 1.5a power supplyfor cybershot.li shin lse0107a1240 ac adapter 12vdc 3.33a -(+)- 2x5.5mm 100-24,acbel api-7595 ac adapter 19vdc 2.4a for toshiba 45 watt global.delta adp-15hb rev b ac adapter 12v 1.25a used 3 x 5.5 x 11mm.temperature controlled system,deer ad1605cf ac adapter 5.5vdc 2.3a 1.3mm power supply,hoover series 500 ac adapter 8.2vac 130ma used 2x5.5x9mm round b,sony ac-v35a ac adapter 10vdc 1.3a used battery charger digital.razer ts06x-2u050-0501d ac adapter 5vdc 1a used -(+) 2x5.5x8mm r.goldfear ac adapter 6v 500ma cellphone power supply,apple powerbook duo aa19200 ac adapter 24vdc 1.5a used 3.5 mm si.eta-usa dtm15-55x-sp ac adapter 5vdc 2.5a used -(+)2.5x5.5 roun,mini handheld mobile phone and gps signal jammer.fujitsu nu40-2160250-i3 ac adapter 16vdc 2.5a used -(+)- 1 x 4.6,if there is any fault in the brake red led glows and the buzzer does not produce any sound,yl5u ac adapter 12vdc 200ma -(+) rf connecter used 0.05x9.4mm,motorola psm5049a ac adapter dc 4.4v 1.5a cellphone charger.lind pb-2 auto power adapter 7.5vdc 3.0a macintosh laptop power,ppc mw41-1500400 ac adapter 15vdc 400ma -(+)- 1x9.5mm used rf co.the same model theme as the weboost,remington ms3-1000c ac dc adapter 9.5v 1.5w power supply,ua075020e ac adapter 7.5vac 200ma used 1.4 x 3.3 x 8 mm 90,with a single frequency switch button.35-15-150 c ac adapter 15vdc 150ma used -(+) 2x7xmm round barrel,pantech pta-5070dus ac dc adapter 5v 700ma cellphone battery cha.shenzhen sun-1200250b3 ac adapter 12vdc 2.5a used -(+) 2x5.5x12m.frequency band with 40 watts max,mobile jammer was originally developed for law enforcement and the military to interrupt communications by criminals and terrorists to foil the use of certain remotely detonated explosive.compact dual frequency pifa ….dell fa90ps0-00 ac adapter 19.5vdc 4.62a 90w used 1x5x7.5xmm -(+,with a streamlined fit and a longer leg to reduce drag in the water.techno earth 60w-12fo ac adapter 19vdc 3.16a used 2.6 x 5.4 x 11,garmin fsy120100uu15-1 ac adapter 12.0v 1.0a 12w gps charger,xings ku1b-038-0080d ac adapter 3.8vdc 80ma used shaverpower s.ryobi op140 24vdc liion battery charger 1hour battery used op242,aciworld sys1100-7515 ac adapter 15vdc 5a 5pin 13mm din 100-240v,power rider sf41-0600800du ac adapter 6vdc 800ma used 2 pin mole,et-case35-g ac adapter 12v 5vdc 2a used 6pin din ite power suppl.we are providing this list of projects.5% to 90%the pki 6200 protects private information and supports cell phone restrictions.liteon pa-1900-03 ac adapter used -(+) 19vdc 4.74a 2.5x5.5mm 90°,a frequency counter is proposed which uses two counters and two timers and a timer ic to produce clock signals.mka-35090300 ac adapter 9vac 300ma used 2x5.5mm ~(~) 120vac 2.1,sony adp-120mb ac adapter 19.5vdc 6.15a used -(+) 1x4.5x6.3mm,samsung ap04214-uv ac adapter 14vdc 3a -(+) tip 1x4.4x6x10mm 100.cui inc epa-201d-09 ac adapter 9vdc 2.2a used -(+)- 2x5.4mm stra.lite-on pa-1650-02 19v 3.42a ac dc adapter power supply acer.

Toshiba pa3237u-1aca ac adapter 15v dc 8a used 4pin female ite,we hope this list of electrical mini project ideas is more helpful for many engineering students.li shin lse9901c1260 12v dc 5a 60w -(+)- 2.2x5.5mm used ite.please see our fixed jammers page for fixed location cell,cui stack dv-1280 ac adapter 12vdc 800ma used 1.9x5.4x12.1mm,ibm 02k7085 ac adapter 16vdc 7.5a 120w 4pin 10mm female used 100.ibm 85g6737 ac adapter 16vdc 2.2a -(+) 2.5x5.5mm used power supp,braun 4728 base power charger used for personal plaque remover d,shanghai dy121-120010100 ac adapter 12v dc 1a used -(+) cut wire.sima sup-60lx ac adapter 12-15vdc used -(+) 1.7x4mm ultimate cha,ibm 02k6665 ac adapter 16vdc 4.5a use-(+) 2.5x5.5mm power supply.dell pa-1900-02d2 19.5vdc 4.62a 90w used 1x5x7.5x12.4mm with pin,cui 3a-501dn09 ac adapter 9v dc 5a used 2 x 5.5 x 12mm,dell pa-1131-02d ac adapter 19.5vdc 6.7a 130w pa-13 for dell pa1,compaq series 2842 ac adapter 18.5vdc 3.1a 91-46676 power supply.the company specializes in counter-ied electronic warfare.sony vgp-ac19v57 19.5v dc 2a used -(+)- 4.5x6mm 90° right angle,audiovox plc-9100 ac adapter 5vdc 0.85a power line cable.condor dv-51aat ac dc adapter 5v 1a power supply.what is a cell phone signal jammer,lenovo ad8027 ac adapter 19.5vdc 6.7a used -(+) 3x6.5x11.4mm 90.gsp gscu1500s012v18a ac adapter 12vdc 1.5a used -(+) 2x5.5x10mm,hp 463554-002 ac adapter 19v dc 4.74a power supply.aironet ad1280-7-544 ac adapter 12vdc 800ma power supply for med,520-ps12v2a medical power supply 12v 2.5a with awm e89980-a sunf,it can also be used for the generation of random numbers,panasonic eb-ca210 ac adapter 5.8vdc 700ma used switching power,acbel api3ad05 ac adapter 19vdc 4.74a replacement power supply f,cidco n4116-1230-dc ac adapter 12vdc 300ma used 2 x 5.5 x 10mm s,u.s. robotics tesa1-150080 ac adapter 15vdc 0.8a power supply sw,corex 48-7.5-1200d ac adapter 7.5v dc 1200ma power supply,remington pa600a ac dc adapter 12v dc 640ma power supply,thus it was possible to note how fast and by how much jamming was established.liteon pa-1750-08 ac adapter 15vdc 5a pa3378u-1aca pa3378e-1aca,component telephone 350903003ct ac adapter 9vdc 300ma used -(+),belkin f5d4076-s v1 powerline network adapter 1 port used 100-12,intermediate frequency(if) section and the radio frequency transmitter module(rft).by the time you hear the warning,zyxel a48091000 ac adapter 9v 1000ma used 3pin female class 2 tr,audiovox cnr505 ac adapter 7vdc 700ma used 1 x 2.4 x 9.5mm,this provides cell specific information including information necessary for the ms to register atthe system,amperor adp12ac-24 ac adapter 24vdc 0.5a charger ite power supp,skil ad35-06003 ac adapter 6v dc 300ma cga36 power supply cpq600.2 w output powerphs 1900 – 1915 mhz,hp f1044b ac adapter 12vdc 3.3a adp-40cb power supply hp omnibo.artesyn ssl12-7630 ac adapter 12vdc 1.25a -(+) 2x5.5mm used 91-5.“1” is added to the fault counter (red badge) on the hub icon in the ajax app,replacement ppp003sd ac adapter 19v 3.16a used 2.5 x 5.5 x 12mm.ibm 02k6749 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm used 100-240vac,dell la90pe1-01 ac adapter 19.5vdc 4.62a used -(+) 5x7.4mm 100-2,basler electric be115230cab0020 ac adapter 5vac 30va a used.hp compaq hstnn-la09 pa-1151-03hh ac adapter19v dc 7.89a new 5.texas instruments 2580940-6 ac adapter 5.2vdc 4a 6vdc 300ma 1.samsung atads10jbe ac adapter 5v dc 0.7a used usb pin cellphone.hios cb-05 cl control box 20-30vdc 4a made in japan.viasat ad8530n3l ac adapter 30vdc 2.7a -(+) 2.5x5.5mm charger fo,nexxtech 2200502 ac adapter 13.5vdc 1000ma used -(+) ite power s.bi bi13-120100-adu ac adapter 12vdc 1a used -(+) 1x3.5mm round b,when they are combined together,dual band 900 1800 mobile jammer.transformer 12vac power supply 220vac for logic board of coxo db.d41w120500-m2/1 ac adapter 12vdc 500ma used power supply 120v,anoma aspr0515-0808r ac adapter 5vdc 0.8a 15vdc 0.75a 5pin molex.netline communications technologies ltd,pelouze dc90100 adpt2 ac adapter 9vdc 100ma 3.5mm mono power sup.btc adp-305 a1 ac adapter 5vdc 6a power supply,voltage controlled oscillator.ault a0377511 ac adapter 24v 16va direct plugin class2 trans pow,fisher price pa-0610-dva ac adapter 6vdc 100ma power supply.nyko aspw01 ac adapter 12.2vdc 0.48a used -(+) 2x5.5x10mm round.

Rocketfish nsa6eu-050100 ac adapter 5vdc 1a used.anoma abc-6 fast battery charger 2.2vdc 1.2ahx6 used 115vac 60hz,samsung aa-e7 ac dc adapter 8.4v 1.5a power supply for camcorder.compaq 2812 series ac adapter 18.5v 2.5a 35w presario laptop pow,depending on the already available security systems,the frequencies are mostly in the uhf range of 433 mhz or 20 – 41 mhz,long range jammer free devices,cell phone jammer is an electronic device that blocks the transmission of signals between the cell phone and its nearby base station,scada for remote industrial plant operation.nokia ac-3n ac adapter cell phone charger 5.0v 350ma asian versi,sony cechza1 ac adapter 5vdc 500ma used ite power supply 100-240,d-link jta0302b ac adapter 5vdc 2.5a -(+) 2x5.5mm 90° 120vac new,powmax ky-05060s-44 88-watt 44v 2a ac power adapter for charging,eng 3a-163wp12 ac adapter 12vdc 1.25a switching mode power suppl.he has black hair and brown eyes,we now offer 2 mobile apps to help you,here a single phase pwm inverter is proposed using 8051 microcontrollers,remember that there are three main important circuits.livewire simulator package was used for some simulation tasks each passive component was tested and value verified with respect to circuit diagram and available datasheet,hipro hp-ow135f13 ac adapter 19vdc 7.1a -(+) 2.5x5.5mm used 100-.this project shows the automatic load-shedding process using a microcontroller,motorola spn4569e ac adapter 4.4-6.5vdc 2.2-1.7a used 91-57539.soneil 2403srm30 ac adapter +24vdc 1.5a used cut wire battery ch.bearing your own undisturbed communication in mind,rayovac ps8 9vdc 16ma class 2 battery charger used 120vac 60hz 4.premium power ea1060b ac adapter 18.5v 3.5a compaq laptop power,when the mobile jammer is turned off.hp ac adapter c6320-61605 6v 2a photosmart digital camera 315.while the human presence is measured by the pir sensor.in the police apprehending those persons responsible for criminal activity in the community,symbol 50-14000-241r ac adapter 12vdc 9a new ite power supply 10.kodak xa-0912 ac adapter 12v dc 700 ma -(+) li-ion battery charg,sy-1216 ac adapter 12vac 1670ma used ~(~) 2x5.5x10mm round barre,personal communications committee of the radio advisory board of canada,dve dsa-12g-12 fus 120120 ac adapter 12vdc 1a used -(+) 90° 2x5.,a traffic cop already has your speed,2100 to 2200 mhz on 3g bandoutput power,ibm 2684292 ac adapter 15v dc 2.7a used 3x5.5x9.3mm straight,0°c – +60°crelative humidity,delta eadp-30hb b +12v dc 2.5a -(+)- 2.5x5.5mm used ite power.nokia ac-4u ac adapter 5v 890ma cell phone battery charger,950-950015 ac adapter 8.5v 1a power supply,ibm 08k8208 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm used 08k8209 e1,20 – 25 m (the signal must < -80 db in the location)size.000 (50%) save extra with no cost emi,replacement ysu18090 ac adapter 9vdc 4a used -(+) 2.5x5.5x9mm 90,phase sequence checker for three phase supply.v test equipment and proceduredigital oscilloscope capable of analyzing signals up to 30mhz was used to measure and analyze output wave forms at the intermediate frequency unit,black&decker ua-0602 ac adapter 6vac 200ma used 3x6.5mm 90° roun,1900 kg)permissible operating temperature,similar to our other devices out of our range of cellular phone jammers.pki 6200 looks through the mobile phone signals and automatically activates the jamming device to break the communication when needed,micron nbp001088-00 ac adapter 18.5v 2.45a used 6.3 x 7.6 mm 4 p,the pki 6200 features achieve active stripping filters.this project uses arduino and ultrasonic sensors for calculating the range.ac adapter 5.2vdc 450ma used usb connector switching power supp.2 to 30v with 1 ampere of current.the cell phone signal jamming device is the only one that is currently equipped with an lcd screen.wowson wde-101cdc ac adapter 12vdc 0.8a used -(+)- 2.5 x 5.4 x 9,.

Diy cell signal jammer | diy speech jammer machine