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Greater Fidelity Using a 3D Approach By Wei Zhang, Attila Komjathy, Simon Banville, and Richard B. Langley INNOVATION INSIGHTS by Richard Langley MAY YOU LIVE IN INTERESTING TIMES. So goes the purported Chinese proverb and curse. When it comes to the ionosphere, an interesting time might indeed be a curse for most users of GPS. The ionosphere – that region of the upper atmosphere where free electrons exist in sufficient numbers to affect the propagation of radio waves – owes its existence primarily to the extreme ultraviolet (EUV) and x-ray photons emitted by the sun. They ionize atoms and molecules in the upper atmosphere, freeing the outer electrons. Mostly the ionosphere is well behaved but it can get quite interesting when it is disturbed by space weather events such as solar flares or coronal mass ejections. The signals from the GPS satellites are perturbed as they transit the ionosphere. Pseudorange measurements are increased in value (an additional delay) and carrier-phase measurements are decreased (a phase advance). If not fully modeled or otherwise accounted for, the perturbations can decrease the accuracy of GPS positioning, navigation, and timing (PNT). For highest PNT accuracies, observations are made at the two frequencies transmitted by all GPS satellites and because the ionosphere’s effect on radio signals is dispersive, a linear combination of the measurements removes almost all of the ionospheric perturbations. On the other hand, the ionosphere’s effect on single frequency observations must be corrected using a model. Most commonly, the model assumes that all of the electrons in the ionosphere can be compressed into a thin shell at a certain height above the receiver. This permits the computation of an estimate of the vertical ionospheric delay. Then, a mapping function is used to predict the slant delay, the delay contributing to a GPS measurement. The approach works reasonably well, particularly if near-real-time values of vertical delay can be provided to users as is done by the Wide Area Augmentation System and other satellite-based augmentation systems. However, this two-dimensional approach ignores the fact that the electron content of the ionosphere is actually spread out in the vertical direction and so has certain inaccuracies, which can increase when the ionosphere is disturbed. In an effort to improve ionosphere modeling with potential application to single-frequency GNSS users, a couple of my current graduate students together with a former student, have investigated a three-dimensional approach to ionospheric modeling using empirical orthogonal functions or EOFs to describe the vertical structure of the ionosphere. EOFs reduce the dimensionality of a data set or an empirical model consisting of a large number of interrelated variables, while retaining as much of the variance present in the data set as possible. This is achieved by transforming to a new set of variables, the orthogonal functions, which are uncorrelated (orthogonal), and which are ordered so that the first few retain most of the variation present in all of the original variables. Only three functions are required to account for more than 99 percent of the variability in the International Reference Ionosphere – 2007, for example. In this month’s column we look at the performance of this 3D approach to modeling the ionosphere including times when the ionosphere is particularly interesting. “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. Ionospheric modeling plays an important role in improving the accuracies of positioning and navigation, especially for current civil aircraft navigation and mass-market single-frequency users. Measurement-driven models are considered to be among the best candidates for real-time single-frequency positioning owing to their real-time applicability and relatively higher accuracy compared to empirical models, such as the GPS broadcast (also known as Klobuchar) and NeQuick models. A good example of a real-time positioning application is satellite-based augmentation systems (SBAS), including the Wide Area Augmentation System (WAAS), the European Geostationary Navigation Overlay Service (EGNOS), the Japanese MSTAT Satellite-based Augmentation System (MSAS), and the Indian GPS Aided Geo Augmented Navigation system (GAGAN). Because the ionosphere can be the largest error source in single-frequency positioning, the accuracy of ionospheric modeling is critical for single-frequency applications. Several organizations have been routinely providing ionospheric products to correct errors caused by the ionosphere in the form of ionospheric maps — that is, vertical total electron content (vTEC) at grid points (including regional and global products), such as those from WAAS and the International GNSS Service (IGS), with various processing time delays ranging from near real time to a couple of weeks. Among the earliest works of ionosphere modeling, the University of New Brunswick-Ionospheric Modeling Technique (UNB-IMT) was developed in the mid-1990s. This technique was demonstrated to effectively derive both regional and global total electron content (TEC) maps. However, most of the models, including the current version of UNB-IMT, approximate the ionosphere using a single thin-shell approach with an altitude set at, for example 350 km, which may introduce additional modeling errors up to several TEC units (1 TECU = 1016 electrons/m2), corresponding to meter-level errors of measurement delay or advance at the GPS L1 frequency. To overcome any downside of such models, three-dimensional (3D) ionospheric tomographic modeling methods have been proposed and implemented by several groups since the late 1990s. Different from the two-dimensional (2D) single thin-shell ionospheric models, where the parameters to be estimated are associated with TEC, the modeled variables in the tomographic model are related to electron density functions. Therefore, we may expect more complex structures of electron densities (such as those observed during ionospheric storms or in the highly variable equatorial anomaly) to be revealed by the models. A commonly accepted modeling approach is to describe the ionospheric horizontal (longitudinal and latitudinal) variability by a spherical harmonic (SH) expansion up to a specific degree and its vertical dimension modeled by empirical orthogonal functions (EOFs). However, SH models are not ideal for capturing local variability in the ionosphere because each basis function of spherical harmonics exists over the entire geographic region of interest, such as the entire globe in the case of global modeling. In other words, localized measurements will have influence on the estimated state across the whole globe. As alternative approaches,  wavelet, finite element (meshes/pixels), and local-basis-function models have been proposed and implemented to capture the localized information content in the measurements and pass this information on to the end user. On the other hand, the inversion process can occasionally become singular as many of the parameters to be estimated tend to be ineffective and less meaningful. This is especially the case when our goal is to obtain better accuracies with higher order wavelet bases or smaller meshes/pixels. Due to the potential computing and transmitting burden, the two modeling techniques may have more difficulties associated with real-time applications, such as real-time single-frequency positioning, although they have advantages for capturing localized structures in the ionosphere. Aiming for potential real-time applications of 3D tomographic models, we have extended the UNB-IMT from 2D to 3D by modeling the vertical dimension of the ionosphere using EOFs. In this article, we discuss our approach and report on some initial tests including comparing its performance with the 3D SH approach. The 2D UNB-IMT was demonstrated to work with various network sizes: regional, baseline-by-baseline, and even single standalone stations. Therefore, it is expected that this technique will help in capturing localized ionospheric structures above small regional networks or above a single standalone station. Additional benefits may be expected for disturbed ionospheric conditions. For assessing the two modeling techniques, a small regional network was chosen to perform station-by-station and batch processes. The performance of both methods with the two processing scenarios has been compared by analyzing the post-fit residuals and vTECs of the state estimation process, as well as the repeatability of estimates of differential code biases (DCBs) for both quiet and disturbed ionospheric conditions. 3D UNB-IMT Because of the limited number of ionospheric parameters to be estimated, the 2D UNB-IMT was considered suitable for real-time applications, such as real-time single-frequency precise point positioning (PPP) and SBASs. In fact, it can be proven that the modeling method of the current 2D UNB-IMT is identical to the original planar fit of WAAS in nature if the locations of reference stations tend to collocate with WAAS ionospheric grid points (IGPs). Although additional parameters are involved, we believe the 3D UNB-IMT approach with its potential for improved modeling accuracy is still suitable for real-time applications. In this section, we will introduce the 3D UNB-IMT modeling strategy and demonstrate its applicability with a regional network and single standalone stations. Model Description. In order to clearly present the technique demonstrated in our recent work, we first briefly review the 2D UNB-IMT. Linear polynomial functions were initially proposed for describing the spatial variability of the ionosphere. We model the observed slant TEC (sTEC) between a satellite and a receiver from carrier-phase and pseudorange (code) observations at some epoch as the product of a bilinear polynomial representing the vTEC at the thin-shell ionospheric pierce point (IPP) of the signal raypath and a mapping function that projects the vTEC to sTEC plus receiver and satellite instrumental biases (DCBs). The input variables are the geographic longitude of the IPP referenced to the solar-geomagnetic coordinate system (in other words, the difference between the longitude of the IPP and the longitude of the mean sun) and the difference between the geomagnetic latitude of the IPP and the geomagnetic latitude of the station. We consequently have three polynomial coefficients to estimate for each station: a constant term, one to describe the longitude variations, and one for the latitude variations. The mapping function used in the model is the standard geometric mapping function, which computes the secant of the zenith angle of the signal geometric ray path at the IPP at a specified shell height. Because of the dependence of the ionosphere on solar radiation and the geomagnetic field, the solar-geomagnetic reference frame is used to compute the TEC over each station in this technique. Since the ionosphere changes more slowly in the sun-fixed reference frame than in the Earth-fixed one, such a reference frame is ideal for producing more accurate TEC estimates. The initial version of UNB-IMT ignored the non-linear spatial variation of the ionosphere. Non-linear terms are expected to be able to absorb more complex variability of the ionosphere and thus more properly describe the ionosphere in disturbed conditions. Regarding this issue, the drawbacks of some modeling methods based on linear models have been reported: for example, the highly variable ionosphere might be absorbed by the estimated DCBs, making the repeatability of the estimated DCBs (day-to-day variability) correlated with the variability of the ionosphere. To enhance the performance of UNB-IMT, especially under disturbed ionospheric conditions, UNB researchers extended the linear version of UNB-IMT to a quadratic one and assessed it by using a wide-area regional network in North America. This modified approach reduced the post-fit residuals significantly by better modeling the ionospheric variations with the help of the additional second order (non-linear) terms. To better use a priori information in the development of 3D UNB-IMT, we separate the TEC into a background reference or “known” part and a perturbation or to-be-modeled part. The background reference part of TEC could be calculated from an a priori source of electron density, such as any kind of ionospheric model, including empirical and theoretical ionospheric models. The density, as a function of latitude, longitude, height, and time, is integrated along the raypath between the receiver and a satellite. Then, the perturbation part of the electron density is modeled by the inner product of EOFs and polynomial functions with associated estimated coefficients to depict the variability of the ionosphere in the vertical and horizontal directions respectively. And this part is similarly integrated along the raypath and added to the reference part along with the DCBs. Empirical Orthogonal Functions. The EOF method is a method of choice for analyzing the variability of a single field (with only one scalar variable). Variability of the ionosphere with respect to height is needed for the 3D models. The method finds the spatial patterns of variability based on historical data sets (as reflected in empirical or theoretical models). In other words, the modes of variability decomposed by the method are primarily “data modes,” and not necessarily physical or actual real-time models. Due to its noted ability in describing the background ionosphere, the data sets output from the empirical Ionospheric Reference Ionosphere 2007, were utilized to form the EOFs in our technique. Thus, the data sets of electron densities are realized by uniform sampling at the following variant time scale intervals and specific geographic locations: Solar cycle: [1998:1:2008] (year) Season of year: [Dec., Mar., Jun., Sep.] (month) Time of day: [1:1:24] (hour) Day of month: [1:9:28] (day of month) Geographic latitude: [30:5:60] (degree)  Geographic longitude: [280:5:300] (degree), where the numbers separated by colons correspond to minimum:increment:maximum. The data sets cover the whole spatial area of interest. The data sets of a whole solar cycle in typical equinox and solstice months are used to ensure that the EOFs span the range of profile variations that include the variation in solar EUV and x-ray output. Each electron density profile with respect to height at these locations and time points is sampled in the vertical dimension at [100:2:2000] (km). Figure 1 shows the first three third-order normalized EOFs based on the data sets. The first three eigenvalues account for 92.22, 6.69, and 0.78 percent of the total respectively. Provided the solution is nonsingular, the choice of the highest order of EOFs is a trade off between processing time and modeling accuracy as to the specific network and capability of computer(s). In our current work, the highest order of three was chosen. In this case, the neglected vertical variation of the ionosphere corresponding to higher order EOFs is 0.31 percent. FIGURE 1. The normalized first three dominant EOFs extracted from the IRI-2007 empirical model. Once the modeling approach has been constructed, the following task is to estimate the coefficients. Considering the potential real-time applications, a Kalman filter is employed to solve the TEC observation equation. To be specific, the following settings are used. The correlation time is set to five minutes, which correspond to the WAAS update interval for ionospheric grid points. The uncertainty of the dynamic model, 0.008 TECU2/second, is chosen to characterize the potential rapid change of the ionosphere. Finally, the estimated coefficients provided by the Kalman filter are then used to reconstruct the electron density field. Testing the Approach In this section, we report on tests of the 3D UNB-IMT and compare its performance with that of the 3D SH approach. Because of the advantages of sensitivity of 2D UNB-IMT, especially with the single-station processing strategy, it is expected that this technique will help in better capturing localized ionospheric structures above small regional networks or above a single standalone station compared to the 3D SH approach. Additional benefits may be expected for disturbed ionospheric conditions. For assessing the two modeling techniques, a small regional network of four IGS reference stations located from geographic latitude 39.0° N to 48.1° N and longitude 66.7° W to 77.6° W was chosen to perform single-station and multi-station (network) processing. The stations are GODZ in Greenbelt, Maryland; UNBJ and FRDN in Fredericton, New Brunswick; and VALD in Val d’Or, Quebec. Figure 2 shows the locations of the reference stations chosen for the modeling. The dual-frequency GPS data used for the tests was obtained from October 13–25 (day of year (doy) 286–298) in 2011 with the sampling time interval of 30 seconds. The corresponding values of the interplanetary magnetic field Bz component; the planetary geomagnetic index, Kp; the auroral electrojet index, AE; and the disturbance storm-time index, Dst on these days are shown in FIGURE 3. It is seen that a severe ionospheric storm triggered by a coronal mass ejection from the sun occurred late on October 24 (doy 297), 2011, and continued through the entire day of October 25 (doy 298), 2011. The other days seem relatively quiet. Thus, we chose October 16, 2011, as a typical day with quiet ionospheric conditions and October 25, 2011, as a typical day with disturbed ionospheric conditions in the following tests. The performance of both methods (3D UNB-IMT and SH model) with the two processing scenarios will be compared by analyzing the post-fit residuals and TEC of the state estimation process for both quiet and disturbed ionospheric conditions. FIGURE 2. The network of the four stations used in the evaluation procedures. All four reference stations in the small network have the ability to provide both C/A- and P-code pseudorange measurements. In our tests, the P-code observable is used to extract TEC through leveling the corresponding carrier-phase measurements. We used a 15°-elevation-angle cut-off in our study. Single Station Experiment. The estimated parameters of 2D and 3D UNB-IMT have different physical meanings due to the different modeling strategies. In theory, the 3D UNB-IMT can reproduce the electron densities for any location (horizontal and vertical) at any epoch. Figure 4 shows an example of the electron density profile produced by the linear 3D UNB-IMT in the zenith direction of station FRDN at 12:00 UT on October 16 (doy 289), 2011. Therefore, we will have to integrate electron densities into TEC for the 3D UNB-IMT modeling results if we want to compare how the two approaches have modeled the ionosphere side by side. For the purpose of sensitivity comparison, the results from 2D and 3D UNB-IMT are compared in terms of post-fit residuals as well as time series of estimated vTEC in the single-station processing scenario. As discussed above, we use the GPS data from station FRDN only for October 16 and 25, 2011, in this subsection. The post-fit residuals are calculated as the difference between the measured and estimated biased sTEC. FIGURE 4. The electron density profile produced by linear 3D UNB-IMT overhead FRDN at 12:00 (UT) on October 16 (doy 289) in 2011. From the top to bottom panels, Figure 5 shows the estimated vTEC in the zenith direction over the station, post-fit residuals, estimated satellite and receiver DCBs, and unbiased sTEC with respect to local mean solar time series obtained with linear 2D (left-hand panels) and 3D (right-hand panels) UNB-IMT approaches respectively. We use a different color for each satellite to see individual improvement of satellites in terms of post-fit residuals, estimated DCB, and unbiased sTEC. As for the potential improvement of 3D UNB-IMT, we supposed, if the 2D model with single-shell assumption does not depict the variability of the ionosphere quite well (especially the vertical variability of the ionosphere), we should expect to see an improvement from the 3D model in terms of post-fit residuals. As seen in this figure, the 3D UNB-IMT improves the results in terms of post-fit residuals. The means and standard deviations of the residuals with the 2D and 3D UNB-IMT are shown in Table 1. FIGURE 5. Sensitivity test (the panels from the top to the bottom correspond to: estimated vertical TEC, post-fit residuals, satellite and receiver DCB, slant TEC with respect to local time) between linear 2D (the left-hand panels) and 3D (the right-hand panels) models at FRDN on October 16 (doy 289) in 2011. TABLE 1. The means and standard deviations of the residuals under the quiet (Q, October 16, 2011) and disturbed or storm (S, October 25, 2011) ionospheric conditions with linear (L) and quadratic (Q) modeling approaches. Units = TECU. The 3D UNB-IMT with three times as many parameters is allowed to “accommodate” more (vertical) variations of the ionosphere. The benefits are also manifest in the improvement of the estimated vTEC and estimated satellite and receiver DCBs. In terms of estimated vTEC, the smooth variation of TEC may be expected at mid-latitudes during quiet ionospheric conditions without any ionospheric anomaly. The unmodeled variation of TEC in 2D UNB-IMT seen in the post-fit residuals is also manifest as “artificial small jumps” in the vTEC panel. In other words, the 3D UNB-IMT is able to better represent the measurements from low-elevation-angle satellites owing to the EOFs replacing the mapping function. It is the typical case when a satellite comes into or goes out of view of the receiver. The estimated DCBs are relatively constant over the entire day. But it is also found from the estimated DCBs that the results from 2D UNB-IMT have slightly more variability. Both effects seem to be related to the unmodeled errors. The post-fit residuals in the 3D UNB-IMT are closer to the zero mean Gaussian distribution. Then, we further evaluated the performance of 2D and 3D UNB-IMT under significantly disturbed conditions. Figure 6 shows the results with the same modeling strategies as demonstrated in Figure 5 but on October 25, 2011. Similar conclusions can be drawn from Figure 6, where better results in terms of post-fit residuals are obtained with 3D UNB-IMT (Table 1). In terms of estimated vTEC, the results from both strategies under the disturbed conditions look more irregular than those under the quiet conditions and deviate a little from the sine-wave-like daily variation. Some actual variation of the ionosphere during disturbed conditions may be captured and correctly illustrated as the bumps for both approaches. Furthermore, the unmodeled errors may also be explained as artificial small jumps/bumps in vTEC curves (revealed by the magnitude of post-fit residuals). It is seen that 3D linear UNB-IMT explains more variation of the ionosphere than 2D linear UNB-IMT. However, some residual unmodeled errors may still exist with the 3D model. FIGURE 6. Sensitivity test (the panels from the top to the bottom correspond to: estimated vertical TEC, residuals, satellite and receiver DCB, slant TEC with respect to local time) between linear 2D (the left-hand panels) and 3D (the right-hand panels) models at FRDN on October 25 (doy 298) in 2011. As concluded by other investigators, a higher order model could explain more spatial (non-linear) variations of the ionosphere, especially for geomagnetic storm conditions. The results with 2D and 3D quadratic UNB-IMT approaches are shown in Figure 7. In the post-fit residual panels, it can be seen that the residuals with 3D quadratic UNB-IMT are mostly within ±2 TECU except for several small spikes that happened between 0:00 and 4:00 local mean solar time and reflect that not all the electron density variations had been correctly represented by the model used. But it is clear that the 3D quadratic UNB-IMT can significantly improve the modeling precision compared to the 2D quadratic/linear UNB-IMT and 3D linear UNB-IMT. The magnitude of the post-fit residuals shown in this panel is even comparable with the results for the quiet condition shown in Figure 5. In terms of vTEC, a few spurious spikes are occasionally found when processing the data from the four stations with the 3D quadratic model and single-station processing strategy. Other data sources, such as data from incoherent backscatter measurements, may be needed to confirm if the spikes are caused by the instability of the model or actual ionospheric structures. Still, the vTEC curves with 3D quadratic UNB-IMT look smoother than 2D UNB-IMT. In terms of estimated DCBs, it is found that the results with 3D quadratic UNB-IMT approach exhibit relatively fewer perturbations than the other three approaches tested. FIGURE 7. Sensitivity test (the panels from the top to the bottom correspond to: estimated vertical TEC, residuals, satellite and receiver DCB, slant TEC with respect to local time) between quadratic 2D (the left-hand panels) and 3D (the right-hand panels) models at FRDN on October 25 (doy 298) in 2011. As we found for the 2D modeling approaches, the single thin-shell assumption with a fixed ionospheric shell height may introduce additional modeling errors. That is mainly because the layer with highest electron density (F2 layer) is not always located at a fixed height. Especially in disturbed ionospheric conditions, such as the case shown in Figures 6 and 7, the layer height would change significantly. Some methods have been proposed and tested with the help of more reliable “true” heights from other resources, such as ionosondes. However, due to the limited number of the instruments deployed and limited information provided (only information from overhead), the applications with these methods would have to be limited to the specific area covered by stations or networks equipped with the instruments. In addition, as to real-time application, the data processing time delay of ionosondes might be another technical issue these methods have to face. Compared with these methods, one benefit of the 3D UNB-IMT is its potential for real-time application for any size of network. Another benefit is its vertical modeling capability to depict vertical variation of electron density so the improved results would also be expected for disturbed ionospheric conditions. It is clearly seen from Figures 6 and 7 that the lowest vTECs around 4:00 LT reach down to 0 TECU with the 2D linear/quatratic UNB-IMT, which are considered as unphysical results. It is confirmed that small biases still exist in the results with the 2D model likely due to the improper shell height chosen (fixed at 350 km for the results shown in this article). Multi-Station Experiment. When using the modeling scheme for a network solution, we will generally have two possible processing scenarios. One is processing the data of all the stations as a batch, and the other is processing station by station (or baseline by baseline). The advantages and disadvantages of the batch process can be summarized as follows. It has more redundancies in the Kalman filter to estimate a more stable and reliable set of satellite and receiver DCBs. Due to more measurements as an input (state) of the Kalman filter, the convergence time would be shorter in terms of the estimated DCBs. It would be of benefit for real-time applications if we have limited a priori information about the estimated ionospheric parameters and/or DCBs. However, the batch solution seems to be less sensitive to localized information content than the station-by-station solution. The overall effect of the batch solution is smoothing over the network, reducing the size of some small perturbations. Theoretically, localized measurements should not have significant influence on the estimated state across an extended area or even the entire globe. In other words, the batch solution may be beneficial for relatively small local-area networks, but may not be ideally suited for networks as large as wide-area ones. Another straightforward disadvantage of the batch process is its relatively longer processing time, which might be a downside if it is used for real-time applications. In the multi-station experiment, we tested the 3D UNB- IMT with a small regional network of four IGS reference stations (Figure 2) to investigate its performance with localized ionospheric variations. We performed tests with two scenarios: batch and station-by-station. Due to space restrictions, we cannot thoroughly report the results we obtained here. Please see the conference paper listed in Further Reading for the full details. Overall, the results we obtained in terms of post-processing residuals were similar to those in the single station experiment. We also found that the 3D UNB-IMT with EOFs seems to be able to better model the measurements with low elevation angles than the 2D UNB-IMT with a mapping function. Comparing 3D UNB-IMT with SH Model. We have compared the results using the batch processing strategy with those from the SH model. The reason for this approach is that we intended to compare the results of the two processing strategies (UNB-IMT and SH) with identical conditions. That is, both methods processed the data using a batch scheme and estimated both ionospheric parameters and DCBs simultaneously, instead of using some other source or processed results. Therefore, in this case, we can compare the results side by side and evaluate the effectiveness of the estimated ionospheric parameters. Based on the data from the network of the four stations, the sensitivity of the SH models is lower than that of 3D UNB-IMT, although the number of ionospheric parameters of the SH models is comparable or even larger than that of 3D UNB-IMT. In other words, the ionospheric parameters in 3D UNB-IMT to describe the variability of the ionosphere are more effective and meaningful to such a network scale than those in the 3D SH model. Given the nature of its basis functions, the SH model is an excellent tool for global modeling, but it has some shortcomings for localized variability modeling. As to larger regional networks with longer baselines, such as those used for WAAS, which covers North America, the difference of the sensitivities between the batch and the station-by-station solutions should be larger than the results we have obtained. However, we cannot conclude that the sensitivity of 3D UNB-IMT is better than that of the 3D SH model with the batch processing strategy for such large regional networks before more tests are conducted. Still, it is clearly seen in our tests that the 3D SH model is not always ideal for regional networks in terms of sensitivity. We reached similar conclusions for October 25, 2011, where the residuals spread more widely compared with quiet-condition residuals. In the storm conditions, the residuals of the quadratic 3D UNB-IMT spread relatively less than those of other modeling strategies. This is especially the case for the several hours at the beginning of the day, which corresponds to the peak of the Dst and Kp indices shown in Figure 3. The quadratic 3D UNB-IMT seems to have the capacity to handle the ionospheric spatial and temporal variation even during severe storm conditions. FIGURE 3. Interplanetary magnetic field Bz component, Kp index, AE index, and Dst index during October 13–25 (doy 286–298) in 2011; nT = nanoteslas (Data from World Data Center for Geomagnetism, Kyoto and Goddard Space Flight Center Space Physics Data Facility). Repeatability of Estimated DCBs. The DCBs not only have influence on the quality (accuracy) of the vTEC estimation, but their repeatability can also provide information to evaluate ionospheric models. This implies that the ionospheric models that have the capability to estimate/eliminate more accurate DCBs, independent of ionospheric variability, are preferable. We carried out a number of tests to evaluate the repeatability of estimated DCB values using the 2D and 3D UNB-IMT approaches as well as the 3D SH technique under both quiet and disturbed ionospheric conditions. For quiet ionospheric conditions, the performance of all the tested models looks comparable, although the quadratic 3D UNB-IMT performs slightly better than the others. As to the disturbed conditions, the quadratic 2D/3D UNB-IMT seems be able to provide more stable DCBs than the other models. However, the improvement of the extension from 2D to 3D is slight for the quadratic models, although it is significant for the linear models. The performance of the 3D SH model looks fairly poor compared to 3D UNB-IMT for regional modeling. Consult the conference paper for further details. Conclusions and Future Research In the work described in this article, we extended the UNB-IMT from 2D to 3D and compared the performance between them in station-by-station and batch processing scenarios for both quiet and storm ionospheric conditions. We used the data from a small regional network of dual-frequency GPS receivers. The DCBs and ionospheric delays were estimated at the same time by a Kalman filter. The newly developed approach was evaluated by analyzing the post-fit residuals, TEC of the state estimation process, and the repeatability of estimates of DCBs. In the single-station processing, the improvement of 3D UNB-IMT has been demonstrated in both quiet and disturbed ionospheric conditions in terms of post-fit residuals. The 3D UNB-IMT with more parameters allows the depiction of more complex (vertical) variability of the ionosphere. The 3D UNB-IMT is able to better deal with the measurements from low-elevation-angle satellites owing to EOFs replacing the mapping function. The artificial jumps with 2D UNB-IMT when satellites come into or go out of view of the receiver have been properly handled by the 3D UNB-IMT. In addition, the time series of estimated DCBs with 3D UNB-IMT exhibit less perturbation than the results with 2D UNB-IMT. As to the multi-station (network) processing, it is confirmed that the station-by-station solution is more sensitive to localized information than the batch solution. Based on the results from our research, station-by-station processing with 3D UNB-IMT is suggested to increase chances to catch localized ionospheric structures. The repeatability of estimated DCBs was investigated as another indicator to evaluate the viability ofionospheric models. Before the 3D UNB-IMT is tested in the positioning domain for single-frequency positioning, it is worth validating the model with other data sources. In addition, the potential benefits of 3D UNB-IMT during extremely disturbed ionospheric conditions is worth investigating further. Acknowledgments We would like to thank the IGS and the Crustal Dynamics Data Information System for providing the GPS data, and we acknowledge the financial contribution of the Natural Sciences and Engineering Research Council of Canada for supporting the first and last authors. This article is based on the paper “Eliminating Potential Errors Caused by the Thin Shell Assumption: An Extended 3D UNB Ionospheric Modelling Technique” presented at the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, September 16–20, 2013. WEI ZHANG received his M.Sc. degree in space science in 2009 from the School of Earth and Space Science of Peking University, China. He is currently an M.Sc.E. student in the Department of Geodesy and Geomatics Engineering at University of New Brunswick (UNB) under the supervision of Dr. Richard B. Langley. ATTILA KOMJATHY is a principal investigator at the California Institute of Technology Jet Propulsion Laboratory and an adjunct professor at UNB, specializing in remote sensing techniques using GPS. He received his Ph.D. from the Department of Geodesy and Geomatics Engineering of UNB in 1997. SIMON BANVILLE works for the Geodetic Survey Division of Natural Resources Canada on real-time precise point positioning (PPP) using global navigation satellite systems. He is also in the process of completing his Ph.D. degree at UNB under the supervision of Dr. Langley. FURTHER READING • Authors’ Conference Paper “Eliminating Potential Errors Caused by the Thin Shell Approximation: An Extended 3D UNB Ionospheric Modelling Technique” by W. Zhang, R.B. Langley, A. Komjathy, and S. Banville in Proceedings of ION GNSS+ 2013, the 26th International Technical Meeting of the Satellite Division of The Institute of Navigation, Nashville, Tennessee, September 16–20, 2013, pp. 2447–2462. • 2D Ionosphere Modeling “SBAS Ionospheric Modeling with the Quadratic Approach: Reducing the Risks” by H. Rho, R. Langley, and A. Komjathy in Proceedings of ION GNSS 2005, the 18th International Technical Meeting of the Satellite Division of The Institute of Navigation, Long Beach, California, September 13–16, 2005, pp. 723–734. Global Ionospheric Total Electron Content Mapping Using the Global Positioning System by A. Komjathy, Ph.D. dissertation, Technical Report No. 188, Department of Geodesy and Geomatics Engineering, University of New Brunswick, Fredericton, New Brunswick, Canada, 1997. “Improvement of a Global Ionospheric Model to Provide Ionospheric Range Error Corrections for Single-frequency GPS Users” by A. Komjathy and R. Langley in Proceedings of the 52nd Annual Meeting of The Institute of Navigation, Cambridge, Massachusetts, January 22–24, 1996, pp. 557–566. • 3D (4D) Ionosphere Modeling “Comparison of 4D Tomographic Mapping Versus Thin-shell Approximation for Ionospheric Delay Corrections for Single-frequency GPS Receivers over North America” by D.J. Allain and C.N. Mitchell in GPS Solutions, Vol. 14, No. 3, 2009, pp. 279–291, doi: 10.1007/s10291-009-0153-0. “Regional 4-D modeling of the Ionospheric Electron Density” by M. Schmidt, D. Bilitza, C. Shum, and C. Zeilhofer in Advances in Space Research, Vol. 42, No. 4, 2008, pp. 782–790, doi: 10.1016/j.asr.2007.02.050. “History, Current State, and Future Directions of Ionospheric Imaging” by G.S. Bust and C.N. Mitchell in Reviews of Geophysics, Vol. 46, No. 1, RG1003, March 2008, doi: 10.1029/2006RG000212. “Development of the Global Assimilative Ionospheric Model” by C. Wang, G. Hajj, X. Pi, I.G. Rosen, and B. Wilson in Radio Science, Vol. 39, No. 1, RS1S06, February 2004, doi: 10.1029/2002RS002854. Contributions to the 3D Ionospheric Sounding with GPS Data by M. García-Fernández, Ph.D. dissertation, Research Group of Astronomy and Geomatics, Universitat Politècnica de Catalunya, Barcelona, Spain, 2004. Available online in three parts: http://www.tesisenred.net/bitstream/handle/10803/7015/01Mgf01de03.pdf?sequence=1 http://www.tesisenred.net/bitstream/handle/10803/7015/01Mgf01de03.pdf?sequence=2 http://www.tesisenred.net/bitstream/handle/10803/7015/01Mgf01de03.pdf?sequence=3. • Ionospheric Reference Models “The NeQuick Model Genesis, Uses and Evolution” by S.M. Radicella in Annals of Geophysics, Vol. 52, No. 3/4, June/August 2009, pp. 417–422, doi: 10.4401/ag-4597. “International Reference Ionosphere 2007: Improvements and New Parameters” by D. Bilitza and B. Reinisch in Advances in Space Research, Vol. 42, No. 4, 2008, pp. 599–609, doi: 10.1016/j.asr.2007.07.048. • Space Weather and the Ionosphere “GNSS and the Ionosphere: What’s in Store for the Next Solar Maximum” by A.B.O. Jensen and C. Mitchell in GPS World, Vol. 22, No. 2, February 2011, pp. 40–48. “Space Weather: Monitoring the Ionosphere with GPS” by A. Coster, J. Foster, and P. Erickson in GPS World, Vol. 14, No. 5, May 2003, pp. 42–49. “GPS, the Ionosphere, and the Solar Maximum” by R.B. Langley in GPS World, Vol. 11, No. 7, July 2000, pp. 44–49. • Empirical Orthogonal Functions “Empirical Orthogonal Functions and Related Techniques in Atmospheric Science: A Review” by A. Hannachi, I.T. Jolliffe, and D.B. Stephenson in International Journal of Climatology, Vol. 27, No. 9, July 2007, pp. 1119–1152, doi: 10.1002/joc.1499. “Empirical Orthogonal Functions: The Medium is the Message” by A.H. Monahan, J.C. Fyfe, M.H.P. Ambaum, D.B. Stephenson, and G.R. North in Journal of Climate, Vol. 22, No. 24, December 2009, pp. 6501–6514, doi: 10.1175/2009JCLI3062.1. A Manual for EOF and SVD Analyses of Climatic Data by H. Bjornsson and S. Venegas, Report No. 97-1, Department of Atmospheric and Oceanic Sciences and Centre for Climate and Global Change Research, McGill University, Montreal, February 1997.

signal jammer antenna

Toshiba pa3743e-1ac3 ac adapter 19vdc 1.58a power supply adp-30j,apple adp-22-611-0394 ac adapter 18.5vdc 4.6a 5pin megnatic used,this project shows charging a battery wirelessly,nokia ac-5e ac adapter cell phone charger 5.0v 800ma euorope ver,ault p48480250a01rg ethernet injector power supply 48vdc 250ma.ingenico pswu90-2000 ac adapter 9vdc 2a -(+) 2.5x5.5 socket jack,phihong psa31u-120 ac adapter 12vdc 2.5a -(+) 2x5.5mm used barre.illum fx fsy050250uu0l-6 ac adapter 5vdc 2.5a used -(+) 1x3.5x9m,i have placed a mobile phone near the circuit (i am yet to turn on the switch),it is created to help people solve different problems coming from cell phones.mastercraft maximum 54-3107-2 multi-charger 7.2v-19.2vdc nicd,here is a list of top electrical mini-projects,surecall's fusion2go max is the cell phone signal booster for you.jvc aa-r602j ac adapter dc 6v 350ma charger linear power supply,premium power pa3083u-1aca ac adapter 15v dc 5a power supply,sanyo scp-06adt ac adapter 5.4v dc 600ma used phone connector po,usually by creating some form of interference at the same frequency ranges that cell phones use,hp hstnn-la01-e ac adapter 19.5vdc 6.9a 135w used -(+) 0.6x5x7.5,if you are using our vt600 anti- jamming car gps tracker.please see the details in this catalogue.sagemcom s030su120050 ac adapter 12vdc 2500ma used -(+) 2.5x5.5m,atlinks 5-2527 ac adapter 9vdc 200ma used 2 x 5.5 x 10mm.hp f1011a ac adapter 12vdc 0.75a used -(+)- 2.1x5.5 mm 90 degree,ad-1235-cs ac adapter 12vdc 350ma power supply.meadow lake tornado or high winds or whatever,motorola psm4562a ac adapter 5.9v dc 400ma used,this paper serves as a general and technical reference to the transmission of data using a power line carrier communication system which is a preferred choice over wireless or other home networking technologies due to the ease of installation.condor hk-h5-a05 ac adapter 5vdc 4a used -(+) 2x5.5mm round barr,sil ssa-12w-09 us 090120f ac adapter 9vdc 1200ma used -(+) 2x5.5.altec lansing acs340 ac adapter 13vac 4a used 3pin 10mm mini din.integrated inside the briefcase,samsung atadu10ube ac travel adapter 5vdc 0.7a used power supply,a mobile phone jammer is an instrument used to prevent cellular phones from receiving signals from base stations.replacement ppp003sd ac adapter 19v 3.16a used 2.5 x 5.5 x 12mm.pride battery maximizer a24050-2 battery charger 24vdc 5a 3pin x.if you can barely make a call without the sound breaking up,all the tx frequencies are covered by down link only,toshiba pa-1121-04 ac dc adapter 19v 6.3a power supplyconditio.band selection and low battery warning led,kyocera txtvl0c01 ac adapter 4.5v 1.5a travel phone charger 2235,l0818-60b ac adapter 6vac 600ma used 1.2x3.5x8.6mm round barrel,in case of failure of power supply alternative methods were used such as generators.this device can cover all such areas with a rf-output control of 10.dve dsa-0151a-12 s ac adapter 12vdc 1.25a used 2.1 x 5.4 x 9.4 m.3com 61-0107-000 ac adapter 48vdc 400ma ethernet ite power suppl.bml 163 020 r1b type 4222-us ac adapter 12vdc 600ma power supply,2100-2200 mhztx output power,sony ac-lm5a ac dc adapter 4.2vdc 1.5a used camera camcorder cha.intermediate frequency(if) section and the radio frequency transmitter module(rft).biogenik s12a02-050a200-06 ac adapter 5vdc 2a used -(+) 1.5x4x9m,ryobi 1400656 1412001 14.4v charger 16v 2a for drill battery.edac ea1060b ac adapter 18-24v dc 3.2a used 5.2 x 7.5 x 7.9mm st,dve dsa-0421s-091 ac adapter used -(+)2.5x5.5 9.5vdc 4a round b.amigo am-121200a ac adapter 12vac 1200ma plug-in class 2 power s.hjc hua jung comp. hasu11fb36 ac adapter 12vdc 3a used 2.3 x 6 x,liteon pa-1600-2-rohs ac adapter 12vdc 5a used -(+) 2.5x5.5x9.7m,when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition,this circuit analysis is simple and easy.3com sc102ta1503b03 ac adapter 15vdc 1.2a power supply,modeling of the three-phase induction motor using simulink,this combined system is the right choice to protect such locations,alvarion 0438b0248 ac adapter 55v 2a universal power supply,powmax ky-05048s-29 battery charger 29vdc 1.5a 3pin female ac ad,rocketfish rf-rzr90 ac adapter dc 5v 0.6a power supply charger,6 different bands (with 2 additinal bands in option)modular protection,0335c2065 advent ac dc adapter 20v 3.25a charger power supply la.while the second one is the presence of anyone in the room,potrans up04821120a ac adapter 12vdc 4a used -(+) 2x5.5x9.7mm ro.yamaha pa-1210 ac adapter 12vdc 1a used -(+) 2x5.5x10mm round ba,nokiaacp-12x cell phone battery uk travel charger,compaq pe2004 ac adapter 15v 2.6a used 2.1 x 5 x 11 mm 90 degree,icm06-090 ac adapter 9vdc 0.5a 6w used -(+) 2x5.5x9mm round barr.energizer tsa9-050120wu ac adapter 5vdc 1.2a used -(+) 1x 3.5mm.dell 0335a1960 ac adapter 19v dc 3.16a -(+)- used 3x5mm 90° ite.panasonic bq-390 wall mount battery charger 1.5v dc 550ma x 4 us.dsa-0151d-12 ac adapter 12vdc 1.5a -(+)- 2x5.5mm 100-240vac powe.jewel jsc1084a4 ac adapter 41.9v dc 1.8a used 3x8.7x10.4x6mm,choose from cell phone only or combination models that include gps.katana ktpr-0101 ac adapter 5vdc 2a used 1.8x4x10mm,it's compatible with all major carriers to boost 4g lte and 3g signals.a user-friendly software assumes the entire control of the jammer.transformer 12vac power supply 220vac for logic board of coxo db,fujitsu 0335c2065 ac adapter 20v dc 3.25a used 2.5x5.5x12.3mm.jvc aa-v11u camcorder battery charger,it’s also been a useful method for blocking signals to prevent terrorist attacks.ibm 02k6750 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm 100-240vac used,hr-091206 ac adapter 12vdc 6a -(+) used 2.4 x 5.4 x 12mm straigh,bell phones dv-1220 dc ac adapter 12vdc 200ma power supply.ault inc 7712-305-409e ac adapter 5vdc 0.6a +12v 0.2a 5pin power.citizen u2702e pd-300 ac adapter 9vdc 300ma -(+) 2x5.5mm used 12,sony bc-csgc 4.2vdc 0.25a battery charger used c-2319-445-1 26-5,in the police apprehending those persons responsible for criminal activity in the community.metro lionville fw 7218m/12 ac adapter 12vdc 1a -(+) used 2x5.5m,delta adp-60bb rev:d used 19vdc 3.16a adapter 1.8 x 4.8 x 11mm,cardio control sm-t13-04 ac adapter 12vdc 100ma used -(+)-,deer computer ad1607c ac adapter 6-7.5v 2.15-1.7a power supply,this covers the covers the gsm and dcs.canon cb-2lu battery charger wall plug-in 4.2v 0.7a i.t.e. power.sil ua-0603 ac adapter 6vac 300ma used 0.3x1.1x10mm round barrel.20 – 25 m (the signal must < -80 db in the location)size.with an effective jamming radius of approximately 10 meters,dc12500 ac adapter 12vdc 500ma power supply class 2 transformer,lien chang lca01f ac adapter 12vdc 4.16a spslcd monitor power,ryobi p113 class 2 battery charger 18v one+ lithium-ion batterie.

Dell pa-1600-06d2 ac adapter 19v dc 3.16a 60w -(+)- used 3x5mm.rocketfish rf-sam90 charger ac adapter 5vdc 0.6a power supply us,hp c8890-61605 ac adapter 6vdc 2a power supply photosmart 210,globtek gt-21097-5012 ac adapter 12vdc 4.17a 50w used -(+) 2.5x5,gps and gsm gprs jammer (gps,k090050d41 ac adapter 9vdc 500ma 4.5va used -(+) 2x5.5x12mm 90°r,compaq pa-1440-3c ac adapter 18.85v 3.2a 45w used 4-pin connecto,motorola fmp5049a travel charger 4.4v 1.5a.a ‘denial-of-service attack’,toshiba pa3378e-3ac3 ac adapter15vdc 5a -(+) 3x6.5mm used round.foreen 35-d12-100 ac adapter12vdc 100ma used90 degree right,bellsouth products dv-9300s ac adapter 9vdc 300ma class 2 transf.it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication.escort zw5 wireless laser shifter.motorola ssw-0828 ac adapter 6.25v 350ma cell phone chargercon.compaq adp-50ch bc ac adapter 18.5vdc 2.7a used 1.8x4.8mm round,dell pa-16 /pa16 ac adapter19v dc 3.16a 60watts desktop power,finecom i-mag 120eu-400d-1 ac adapter 12vdc 4a -(+) 1.7x4.8mm 10.hp adp-65hb n193 bc ac adapter 18.5vdc 3.5a used -(+) ppp009d.symbol vdn60-150a battery adapter 15vdc 4a used -(+)- 2.5x5.5mm,please visit the highlighted article,oem ad-0680 ac adapter 6vdc 800ma used -(+) 1.1x3.5x11mm round b,soft starter for 3 phase induction motor using microcontroller,emerge retrak etchg31no usb firewire 3 in 1 car wall charger.dell pa-1151-06d ac adapter 19.5vdc 7.7a used -(+) 1x4.8x7.5mm i,eng 3a-122wp05 ac adapter 5vdc 2a -(+) 2.5x5.5mm black used swit,targus apa30ca 19.5vdc 90w max used 2pin female ite power supply,liteon pa-1300-04 ac adapter 19vdc 1.58a laptop's power supply f,this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db,this circuit uses a smoke detector and an lm358 comparator,ault pw15aea0600b05 ac adapter 5.9vdc 2000ma used -(+) 1.3x3.5mm,condor a9500 ac adapter 9vac 500ma used 2.3 x 5.4 x 9.3mm,jammers also prevent cell phones from sending outgoing information.tectrol kodak nu60-9240250-13 ac adapter 24v 2.5a ite power supp,pa-1121-02hd replacement ac adapter 18.5v 6.5a laptop power supp,fujitsu ca01007-0520 ac adapter 16vdc 2.7a laptop power supply,canon ca-cp200 ac adapter 24vdc 2.2a used 2.5x5.5mm straight rou,replacement 75w-hp21 ac adapter 19vdc 3.95a -(+) 2.5x5.5mm 100-2,philips 4203-035-77410 ac adapter 2.3vdc 100ma used shaver class,this cooperative effort will help in the discovery,nec pa-1700-02 ac adapter 19vdc 3.42a 65w switching power supply,altec lansing a1664 ac adapter 15vdc 800ma used -(+) 2x,if you are in the united states it is highly illegal to own,motorola spn4366c ac adapter 8vdc 1a 0.5x2.3mm -(+) cell phone p,nexxtech e201955 usb cable wall car charger new open pack 5vdc 1,netcom dv-9100 ac adapter 9vdc 100ma used -(+) 2.5x5.5mm straigh.condor aa-1283 ac adapter 12vdc 830ma used -(+)- 2x5.5x8.5mm rou,we just need some specifications for project planning.gn netcom ellipe 2.4 base and remote missing stand and cover,chicony a10-018n3a ac adapter 36vdc 0.5a used 4.3 x 6 x 15.2 mm,simran sm-50d ac adapter 220v 240v new up-down converter fuse pr,kodak k630 mini charger aa 0r aaa used class 2 battery charger e.canon cb-2ly battery charger for canon nb-6l li-ion battery powe,bionx sa190b-24u ac adapter 26vdc 3.45a -(+)- 89.7w charger ite,esaw 450-31 ac adapter 3,4.5,6,7.5,9-12vdc 300ma used switching,teamgreat t94b027u ac adapter 3.3vdc 3a -(+) 2.5x5.4mm 90 degree.audiovox cnr505 ac adapter 7vdc 700ma used 1 x 2.4 x 9.5mm,dura micro pa-215 ac adapter 12v 1.8a 5v 1.5a dual voltage 4pins,8 watts on each frequency bandpower supply,top global wrg20f-05ba ac adapter 5vdc 4a -(+)- 2.5x5.5mm used,aastra m8000 ac adapter 16vac 250ma ~(~) 2.5x5.5m.panasonic cf-aa1653a j1 ac adapter 15.6v 5a used 2.7 x 5.4 x 9.7,8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices.ault cs240pwrsup ac adapter 7.5vdc 260ma used 9.0vac 250ma,temperature controlled system,best seller of mobile phone jammers in delhi india buy cheap price signal blockers in delhi india.sunny sys1148-3012-t3 ac adapter 12v 2.5a 30w i.t.e power supply,courier charger a806 ac adaptr 5vdc 500ma 50ma used usb plug in.recoton ad300 adapter universal power supply multi voltage,datalogic sc102ta0942f02 ac adapter 9vdc 1.67a +(-) 2x5.5mm ault,samsung sbc-l5 battery charger used 4.2v 415ma class 2 power sup.iomega wa-05e05 u ac adapter 5vdc 1a used 2.5 x 5.5 x 11mm,auto charger 12vdc to 5v 0.5a car cigarette lighter mini usb pow.toshibapa-1900-24 ac adapter 19vdc 4.74a 90w pa3516a-1ac3 powe,atlinks 5-2418a ac adapter 9vac 400ma ~(~) 2x5.5mm 90° used 120v.bs-032b ac/dc adapter 5v 200ma used 1 x 4 x 12.6 mm straight rou,this project shows the system for checking the phase of the supply,rocketfish mobile rf-mic90 ac adapter 5vdc 0.6a used,dewalt d9014-04 battery charger 1.5a dc used power supply 120v.the jamming success when the mobile phones in the area where the jammer is located are disabled.ast ad-4019 eb1 ac adapter 19v 2.1a laptop power supply,ps06b-0601000u ac adapter used -(+) 6vdc 1000ma 2x5.5mm round ba.military attacking jammer systems | jammer 2,nyko aspw01 ac adapter 12.2vdc 0.48a used -(+) 2x5.5x10mm round,ching chen wde-101cdc ac dc adapter 12v 0.8a power supply.cgo supports gps+glonass+beidou data in.air rage u060050d ac adapter 6vdc 500ma 8w -(+)- 2mm linear powe.ceiva2 jod-smu02130 ac adapter 5vdc 1.6a power supply,coleman cs-1203500 ac adapter 12vdc 3.5a used -(+) 2x5.5x10mm ro,dell pscv360104a ac adapter 12vdc 3a -(+) 4.4x6.5mm used 100-240.tdp ep-119/ktc-339 ac adapter 12vac 0.93amp used 2.5x5.5x9mm rou,mastercraft sa41-6a battery carger 7.2vdc used -(+) power supply.sl waber ds2 ac adapter 15a used transiet voltage surge suppress,toshiba pa-1900-03 ac adapter used -(+) 19vdc 4.74a 2.5x5.5mm la,audiovox ad-13d-3 ac adapter 24vdc 5a 8pins power supply lcd tv,vipesse a0165622 12-24vdc 800ma used battery charger super long,phihong psaa18u-120 ac adapter 12vdc 1500ma used +(-) 2x5.5x12mm,fidelity electronics u-charge new usb battery charger 0220991603.honeywell 1321cn-gt-1 ac adapter 16.5vac 25va used class 2 not w,ccm sdtc8356 ac adapter 5-11vdc used -(+)- 1.2x2.5x9mm,ault sw172 ac adapter +12vdc 2.75a used 3pin female medical powe.ault pw125ra0900f02 ac adapter 9.5vdc 3.78a 2.5x5.5mm -(+) used,it is specially customised to accommodate a broad band bomb jamming system covering the full spectrum from 10 mhz to 1.sony dcc-fx110 dc adapter 9.5vdc 2a car charger for dvpfx810.

Olympus a511 ac adapter 5vdc 2a power supply for ir-300 camera.anoma electric aec-t5713a ac adapter 13.5vdc 1.5a power supply.chc announced today the availability of chc geomatics office (cgo).go through the paper for more information,sony ac-64na ac adapter 6vdc 400ma used -(+)- 1.8x4x9.7mm,t4 spa t4-2mt used jettub switch power supply 120v 15amp 1hp 12,jabra fw7600/06 ac adapter 6vdc 250ma used mini 4pin usb connec,dell da90ps1-00 ac adapter 19.5vdc 4.62a used straight with pin,just mobile 3 socket charger max 6.5a usb 1a 5v new in pack univ,changzhou jt-24v450 ac adapter 24~450ma 10.8va used class 2 powe.sino-american sa120a-0530v-c ac adapter 5v 2.4a class 2 power su.linearity lad6019ab4 ac adapter 12vdc 4a-(+)- 2.5x5.5mm 100-24.kodak k5000 li-ion battery charger4.2vdc 650ma for klic-5000 kli.we are talking for a first time offender up to 11,people might use a jammer as a safeguard against sensitive information leaking,mastercraft maximum dc14us21-60a battery charger 18.8vdc 2a used,black & decker ua060020 ac adapter 6v ac ~ 200ma used 2x5.5mm,swingline ka120240060015u ac adapter 24vdc 600ma plug in adaptor.philishave 4203 030 76580 ac adapter 2.3vdc 100ma new 2 pin fema.cyber acoustics md-75350 ac adapter 7.5vdc 350ma power supply,sony ac-fd008 ac adapter 18v 6.11a 4 pin female conector,ati eadp-20fb a ac adapter 5vdc 4a -(+) 2.5x5.5mm new delta elec.daveco ad-116-12 ac adapter 12vdc 300ma used 2.1 x 5.4 x 10.6 mm.check your local laws before using such devices,cobra ga-cl/ga-cs ac adapter 12vdc 100ma -(+) 2x5.5mm power supp,best a7-1d10 ac dc adapter 4.5v 200ma power supply.energizer fm050012-us ac adapter 5v dc 1.2a used 1.7x4x9.7mm rou,psp electronic sam-pspeaa(n) ac adapter 5vdc 2a used -(+) 1.5x4x,sharp ea-28a ac adapter 6vdc 300ma used 2x5.5x10mm round barrel.austin adp-bk ac adapter 19v dc 1.6a used 2.5x5.5x12.6mm,who offer lots of related choices such as signal jammer,the civilian applications were apparent with growing public resentment over usage of mobile phones in public areas on the rise and reckless invasion of privacy,ibm aa21131 ac adapter 16vdc 4.5a 72w 02k6657 genuine original.li shin 0217b1248 ac adapter 12vdc 4a -(+)- 2x5.5mm 100-240vac p.macintosh m4328 ac adapter 24.5vdc 2.65a powerbook 2400c 65w pow,uniden ad-1011 ac adapter 21vdc 100ma used -(+) 1x3.5x9.8mm 90°r,cable shoppe inc oh-1048a0602500u-ul ac adapter 6vdc 2.5a used,akii technology a10d2-09mp ac adapter +9vdc 1a 2.5 x 5.5 x 9.3mm.condor 48a-9-1800 ac adapter 9vac 1.8a ~(~) 120vac 1800ma class,ps0538 ac adapter 5vdc 3.5a - 3.8a used -(+)- 1.2 x 3.4 x 9.3 mm,nikon coolpix ni-mh battery charger mh-70 1.2vdc 1a x 2 used 100.ah-v420u ac adapter 12vdc 3a power supply used -(+) 2.5x5.5mm.dve dsa-12pfa-05 fus 050200 ac adapter +5vdc 2a used -(+) 0.5x2x,sanyo var-33 ac adapter 7.5v dc 1.6a 10v 1.4a used european powe,specialix 00-100000 ac adapter 12v 0.3a rio rita power supply un,landia p48e ac adapter 12vac 48w used power supply plug in class.hp f1454a ac adapter 19v 3.16a used -(+) 2.5x5.5mm round barrel.panasonic ag-b6hp ac adapter 12vdc 1.8a used power supply,mobile jammer seminar report with ppt and pdf jamming techniques type 'a' device,toshiba sadp-65kb d ac adapter 19v dc 3.43a used 2.5x5.5x11.9mm,cell phone jammer is an electronic device that blocks transmission of ….toshiba pa2440u ac adapter 15vdc 2a laptop power supply.condor dv-51aat ac dc adapter 5v 1a power supply.blackberry psm24m-120c ac adapter 12vdc 2a used rapid charger 10.hp hstn-f02g 5v dc 2a battery charger with delta adp-10sb.symbol b100 ac adapter 9vdc 2a pos bar code scanner power supply,40 w for each single frequency band.blackbox jm-18221-na ac adapter 18vac c.t. 2.22a used cut wire,to duplicate a key with immobilizer,hipro hp-a0904a3 ac adapter 19vdc 4.74a 90w used -(+)- 2x5.5mm 9.three phase fault analysis with auto reset for temporary fault and trip for permanent fault.nokia acp-8u ac adapter 5.3v dc 500ma power supply for nokia cel,apple m7332 yoyo ac adapter 24vdc 1.875a 3.5mm 45w with cable po.ac adapter 220v/120v used 6v 0.5a class 2 power supply 115/6vd,minolta ac-7 ac-7e ac adapter 3.4vdc 2.5a -(+) 1.5x4mm 100-240va,panasonic cf-aa1639 m17 15.6vdc 3.86a used works 1x4x6x9.3mm - 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