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Handling the Biases for Improved Triple-Frequency PPP Convergence By Denis Laurichesse Precise point positioning (PPP) can be considered a viable tool in the kitbag of GPS positioning techniques. One precision aspect of PPP is its use of carrier-phase measurements rather than just pseudoranges. But there is a catch. Often many epochs of measurements are needed for a position solution to converge to a sufficiently high accuracy. In this month’s column, we look at how using measurements from three satellite frequencies rather than just two can help. INNOVATION INSIGHTS by Richard Langley PPP? WHAT’S THAT? This acronym stands for precise point positioning and, although the technique is still in development, it has evolved to a stage where it can be considered another viable tool in the kitbag of GPS positioning techniques. It is now supported by a number of receiver manufacturers and several free online PPP processing services. You might think, looking at the name, that there’s nothing particularly special about it. After all, doesn’t any kind of positioning with GPS give you a precise point position including that from a handheld receiver or a satnav device? They key word here is precise. The use of the word precise, in the context of GPS positioning, usually means getting positional information with precision and accuracy better than that afforded by the use of L1 C/A-code pseudorange measurements and the data provided in the broadcast navigation messages from the satellites. A typically small improvement in precision and accuracy can be had by using pseudoranges determined from the L2 frequency in addition to L1. This permits the real-time correction for the perturbing effect of the ionosphere. Such an improvement in positioning is embodied in the distinction between the two official GPS levels of service: the Standard Positioning Service provided through the L1 C/A-code and the Precise Positioning Service provided for “authorized” users, which requires the use of the encrypted P-code on both the L1 and L2 frequencies. Civil GPS users will have access to a similar level of service once a sufficient number of satellites transmitting the L2 Civil (L2C) code are in orbit. However, this capability will only provide meter-level accuracy. The PPP technique can do much better than this. It can do so thanks to two additional precision aspects of the technique. The first is the use of more precise (and, again, accurate) descriptions of the orbits of the satellites and the behavior of their atomic clocks than those included in the navigation messages. Such data is provided, for example, by the International GNSS Service (IGS) through its global tracking network and analysis centers. These so-called precise products are typically used to process receiver data after collection in a post-processing mode, although real-time correction streams are now being provided by the IGS and some commercial entities. Now, it’s true that a user can get high precision and accuracy in GPS positioning using the differential technique where data from one or more base or reference stations is combined with data from the user receiver. However, by using precise products and a very thorough model of the GPS observables, the PPP technique does away with the requirement for a directly accessed base station. The other precision aspect of PPP is its use of carrier-phase measurements rather than just pseudoranges. Carrier-phase measurements have a precision on the order of two magnitudes (a factor of 100) better than that of pseudoranges. But there is a catch to the use of carrier-phase measurements: they are ambiguous by an integer multiple of one cycle. Processing algorithms must resolve the value of this ambiguity and ideally fix it at its correct integer value. Unfortunately, it is difficult to do this instantaneously, and often many epochs of measurements are needed for a position solution to converge to a sufficiently high accuracy, say better than 10 centimeters. Researchers are actively working on reducing the convergence time, and in this month’s column, we look at how using measurements from three satellite frequencies rather than just two can help. “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. To contact him, see the “Contributing Editors” section on page 6. While carrier-phase measurements typically have very low noise compared to pseudorange (code) measurements, they have an inherent integer cycle ambiguity: the carrier phase, interpreted as a range measurement, is ambiguous by any number of cycles. However, integer ambiguity fixing is now routinely applied to undifferenced GPS carrier-phase measurements to achieve precise positioning. Some implementations are even available in real time. This so-called precise point positioning (PPP) technique permits ambiguity resolution at the centimeter level. With the new modernized satellites’ capabilities, performing PPP with triple-frequency measurements will be possible and, therefore, the current dual-frequency formulation will not be applicable. There is also a need for a generalized formulation of phase biases for Radio Technical Commission for Maritime Services (RTCM) State Space Representation (SSR) needs. In this RTCM framework, the definition of a standard is important to allow interoperability between the two components of a positioning system: the network side and the user side. Classical Formulation In this section, we review the formulation of the observation equations. We will use the following constants in the equations: where f1 and f2 are the two primary frequencies transmitted by all GPS satellites and c is the vacuum speed of light. For the GPS L1 and L2 bands, f1 = 154f0 and f2 = 120f0, where f0 = 10.23 MHz. The pseudorange (or code) measurements, P1 and P2, are expressed in meters, while phase measurements, L1 and L2, are expressed in cycles. In the following, we use the word “clock” to mean a time offset between a receiver or satellite clock and GPS System Time as determined from either code or phase measurements on different frequencies or some combination of them. The code and phase measurements are modeled as:   (1) where: D1 and D2 are the geometrical propagation distances between the emitter and receiver antenna phase centers at f1 and f2 including troposphere elongation, relativistic effects and so on. W is the contribution of the wind-up effect (in cycles). e is the code ionosphere elongation in meters at f1. This elongation varies with the inverse of the square of the carrier frequency and is applied with the opposite sign for phase. Δh = hi – hj is the difference between receiver i and emitter j ionosphere-free phase clocks. Δhp is the corresponding term for code clocks. Δτ = τi – τj is the difference between receiver i and emitter j offsets between the phase clocks at f1 and the ionosphere-free phase clocks. By construction, the corresponding quantity at f2 is γΔτ. Similarly, the corresponding quantity for the code is Δτp (time group delay). N1 and N2 are the two carrier-phase ambiguities. By definition, these ambiguities are integers. Unambiguous phase measurements are therefore L1 + N1 and L2 + N2. Equations (1) take into account all the biases related to delays and clock offsets. The four independent parameters, Δh, Δτ, Δhp, and Δτp, are equivalent to the definition of one clock per observable. However, our choice of parameters emphasizes the specific nature of the problem by identifying reference clocks for code and phase (Δhp and Δh) and the corresponding hardware offsets (Δτp and Δτ). These offsets are assumed to vary slowly with time, with limited amplitudes. The measured widelane ambiguity,  , (also called the Melbourne-Wübbena widelane) can be written as: (2) where Nw is the integer widelane ambiguity, μ j is the constant widelane delay for satellite j and μi is the widelane delay for receiver i (which is fairly stable for good quality geodetic receivers). The symbol  means that all quantities have been averaged over a satellite pass. Integer widelane ambiguities are then easily identified from averaged measured widelanes corrected for satellite widelane delays. Once integer widelane ambiguities are known, the ionosphere-free phase combination can be expressed as   (3) where     is the ionosphere-free phase combination computed using the known Nw ambiguity, Dc is the propagation distance, hi is the receiver clock and h j is the satellite clock. N1 is the remaining ambiguity associated to the ionosphere-free wavelength λc (10.7 centimeters). The complete problem is thus transformed into a single-frequency problem with wavelength λc and without any ionosphere contribution. Many algorithms can be used to solve Equation (3) using data from a network of stations. If Dc is known with sufficient accuracy (typically a few centimeters, which can be achieved using a good floating-point or real-valued ambiguity solution), it is possible to simultaneously solve for N1 , hi and h j. The properties of such a solution have been studied in detail. A very interesting property of the h j satellite clocks is, in particular, the capability to directly fix (to the correct integer value) the N1 values of a receiver that was not part of the initial network. The majority of the precise-point-positioning ambiguity-resolution (PPP-AR) implementations are based on the identification and use of the two quantities μ j and h j. These quantities may be called widelane biases and integer phase clocks, a decoupled clock model or uncalibrated phase delays, but they are all of the same nature. A Real-Time PPP-AR Implementation A PPP-AR technique was successfully implemented by the Centre National d’Etudes Spatiales (CNES) in real time in the so-called PPP-Wizard demonstrator in 2010 and has been subsequently improved. In this demonstrator and in the framework of the International GNSS Service (IGS) Real-Time Service (RTS) and the RTCM, the GPS and GLONASS constellation orbits and clocks are computed. Additional biases for GPS ambiguity resolution are computed and broadcast to the user. The demonstrator also provides an open-source implementation of the method on the user side, for test purposes. Centimeter-level positioning accuracy in real time is obtained on a routine basis. Limitations of the Bias Formulations. The current formulation works but it has several drawbacks: The chosen representation is dependent on the implemented method. Even if the nature of the biases is the same, their representation may be different according to the underlying methods, and this makes it difficult for a standardization of the bias messages. The user side must implement the same method as the one used on the network side. Otherwise, the user side would have to convert the quantities from one method to another, leading to potential bugs or misinterpretations. It is limited to the dual-frequency case. There are only two quantities to be computed in the dual-frequency case ( and ), but in the triple-frequency case, there are many more possible combinations. For example, one can have (this is a non-exhaustive list) , , ,, , , where the indices refer to different pairs of frequencies, and other ionosphere-free combinations such as phase widelane-only or even phase ionosphere-free and geometry-free combinations are possible. New RTCM SSR Model The new model, as proposed by the RTCM Special Committee 104 SSR working group for phase bias messages is based on the idea that the phase bias is inherent to each frequency. Thus, instead of making specific combinations, one phase bias per phase observable is identified and broadcast. It is noted that this convention was adopted a long time ago for code biases. Indeed, in the RTCM framework, and unlike the standard differential code bias (DCB) convention where code biases are undifferenced but combined, the RTCM SSR code biases are defined as undifferenced and uncombined. The general model for uncombined code and phase biases is therefore:    (4) Time group delays, τ, and phase clocks, h, in Equation (1) are replaced by code and phase biases (ΔbP and ΔbL respectively). RTCM SSR code and phase biases correspond to the satellite part of these biases. The prime notation denotes the “unbiasing” process of the measurements. Here, the clock definition is crucial. As the biases are uncombined, they are referenced to the clocks. The convention chosen for the standard is natural: it is the same as the one used by IGS, that is, ΔhP in our notation. This new model can be extended to the triple-frequency case very easily, as it does not involve explicit dual-frequency combinations:     (5) This new model simplifies the concept of phase biases for ambiguity resolution. This representation is very attractive because no assumption is made on the method used to identify phase biases on the network side. All the implementations are valid if they respect this proposed model. It also allows convenient interoperability if the network and user sides implement different ambiguity resolution methods. TABLE 1 summarizes the different messages used for PPP-AR in the context of RTCM SSR: TABLE 1. RTCM SSR messages for PPP-AR. Bias Estimation in the Dual-Frequency Case. The new phase biases identification in the dual-frequency case is straightforward. There are two biases (,  ) to be estimated using two combinations (µ and h). The problem to be solved is described in FIGURE 1. FIGURE 1. Phase biases estimation in the dual-frequency case. It can be solved very easily on the network side by means of a 2 × 2 matrix inversion:    (6) with Note: All the quantities denote the satellite part of the Δ operator defined above. Bias Estimation in the Triple-Frequency Case. The triple-frequency bias identification is tricky due to the need, using only three biases, to keep the integer nature of phase ambiguities on all viable ionosphere-free combinations, and in particular combinations that were not used in the identification process. At this level, one cannot make assumptions on what kind of combinations will be employed by a user. The problem to be solved is described in FIGURE 2. FIGURE 2. Phase biases estimation in the triple-frequency case. As an example, a naïve solution would be to identify the extra-widelane phase biases,, using the dual-frequency widelane approach, and then identify thebias. Given the large wavelength of the extra-widelane combination, such identification would be very easy. However, the corresponding bias would be only helpful for extra-widelane ambiguity identification, and its noise would prevent its use for widelane 15 (L1/L5) ambiguity resolution or other useful combinations available in the triple-frequency context. Each independent phase bias can be directly estimated in a filter; however, in order to keep ascending compatibility with the dual-frequency case during the deployment phase of the new modernized satellites, we have chosen to stay in the old framework, that is, to work with combinations of biases. The resolution method is the following: The widelane biases, that is, the identification of all the bLi – bLj quantities, are solved. For this computation and in order to have an accurate estimate of these biases, the two MW-widelane biases µ12 and µ15 are used coupled to an additional phase bias, which is given by the triple-frequency ionosphere-free phase combination with the integer widelane ambiguities already fixed. This last combination using only phase measurements is much more accurate than MW-widelanes. The system to be solved is redundant and the noise of the different equations has to be chosen carefully. The remaining bias (bLi ) is estimated using the traditional ionosphere-free phase combination of L1 and L2. This computation has been implemented in the CNES real-time analysis center software, and since September 15, 2014, CNES broadcasts phase biases compatible with this triple-frequency concept on the IGS CLK93 real-time data stream. Real Data Analysis To prove the validity of the concept, at CNES, we compute several ambiguity combinations using real data. The process is the following: Look for good receiver locations having a large number of GPS Block IIF satellites (transmitting the L5 signal) in view for a period of time exceeding 30 minutes, and choose among them, one participating in the IGS Multi-GNSS (MGEX) experiment. The station CPVG (Cape Verde) in the Reseau GNSS pour l’IGS et la Navigation (REGINA) network was chosen for the time span on September 28, 2014, between 19 and 20 hours UTC. During this period, four Block IIF satellites were visible simultaneously (PRNs 1, 6, 9, 30) for a total of 14 GPS satellites in view. Record a compatible phase-bias stream. The CLK93 stream is recorded during the time span of the experiment. Perform a PPP solution using the measurements, CLK93 corrections and biases to estimate the propagation distance, the troposphere delay and the receiver clock and phase ambiguity estimates according to Equation (5). For different ambiguity estimates, compute and plot the obtained residuals. We present in the following graphs various ambiguity residuals for the four Block IIF satellites in view. The values of each ambiguity are offset by an integer value for clarity purposes. Melbourne-Wübbena Extra-Widelane. FIGURE 3 represents the MW extra-widelane (between frequencies L2 and L5) ambiguity estimation using our process. The MW extra-widelane ambiguity has a wavelength of 5.86 meters. The noise of the combination expressed in cycles is very low, and the integer nature of ambiguities in this combination is clearly visible. FIGURE 3. Ambiguity residuals for the extra-widelane 5-2 combination. Melbourne-Wübbena Widelanes. FIGURE 4 represents the MW-widelanes (the regular 1-2 and 1-5 combinations). Here again, the integer nature of the four ambiguities is clearly visible. FIGURE 4. Ambiguity residuals for widelane combinations; top: 1-2 widelane, bottom: 1-5 widelane. Widelane-Only Ionosphere-Free Phase. In the triple-frequency context, there is a possibility of forming an ionosphere-free combination of the three phase observables. This combination has an important noise amplification factor (>20), but would allow us to perform decimeter-accuracy PPP using only the solved widelane integer ambiguities and if the corresponding phase biases are accurate. In addition, it can be shown that the wavelength of the widelane ambiguity when the extra-widelane ambiguity is solved is about 3.4 meters. It means that the remaining widelane using this combination can be solved if the position is accurate enough (a few tens of centimeters) and the extra-widelane is known. FIGURE 5 shows such a case, that is, the residuals of the widelane ambiguity using this combination and assuming that the extra-widelane is already solved for. FIGURE 5. Ambiguity residuals for widelane-only 1-2-5 ionosphere free combinations. Such a case where the solution is the most biased  is shown (the dark blue curve). This behavior is mainly due to the difficulty in estimating the phase biases on this combination accurately using only a few Block IIF satellites. We hope that in the future the increasing number of modernized satellites will help such bias estimation. N1 Ionosphere-Free Phase. FIGURES 6 to 8 show the three possible ambiguity estimates using the ionosphere-free phase combination with two measurements (we assume that the corresponding widelane has already been solved). In each case, the computed biases allow us to easily retrieve the integer nature of the N1 ambiguity. FIGURE 6. Ambiguity residuals for the N1 combination using a fixed 1-2 widelane. FIGURE 7. Ambiguity residuals for the N1 combination using a fixed 1-5 widelane. FIGURE 8. Ambiguity residuals for the N1 combination using a fixed 2-5 widelane. Application to Triple-Frequency PPP The results presented above show that the integer ambiguity nature of phase measurements is conserved for various useful observable combinations and prove the validity of the model. Another experiment has been carried out to estimate the impact of ambiguity convergence in the triple-frequency context. For that, in order to maximize the observability of the GPS Block IIF constellation and thus the accuracy of the biases, a network of ten stations across Europe has been chosen for the phase biases computation (see FIGURE 9). The station REDU (in green) was the test station to be positioned. The test occurred on January 10, 2015, around 11:00 UTC. At that time, four Block IIF satellites were visible simultaneously (PRNs 1, 3, 6, 9) for a total of 10 satellites in view. FIGURE 9. Network used for the triple-frequency PPP study. The PPP-Wizard open source client was used to perform PPP in real time. The advantage of this implementation is that it directly follows the uncombined observable formulation described in Equations (5). The strategy for ambiguity resolution is a simple bootstrap approach. Convergence of the Widelane-Only Solution. In this test, a PPP solution was performed, but only the fixing of the widelane ambiguities was implemented. As noted in the previous section, the wavelength of the widelane ambiguity when the extra-widelane ambiguity is solved is about 3.4 meters, so it is expected that all the widelanes can be fixed in a very short time. Despite the amplification factor of about 20 of the equivalent unambiguous phase combination, we expect to obtain an accuracy of about 10 centimeters with such a solution. FIGURE 10 shows the convergence time of several PPP runs in this context (16 different runs of five minutes are superimposed), in terms of horizontal position error. FIGURE 10. Widelane-only triple-frequency PPP convergence (horizontal position error). The extra-widelanes are fixed instantaneously; the remaining widelanes are fixed in about two minutes on average to be below 30 centimeters (this is represented by the different sharp reductions of the errors). This new configuration, available in the triple-frequency context, is very interesting as it provides an intermediate class of accuracy, which converges very quickly and which is suitable for applications that do not demand centimeter accuracy. Another interesting aspect of this combination is the gap-bridging feature. In PPP, gap-bridging is the functionality that allows us to recover the integer nature of the ambiguities after a loss of the receiver measurements over a short period of time (typically a pass through a tunnel or under a bridge). This is done usually by means of the estimation of a geometry-free combination (ionosphere delay estimation) during the gap. Realistic maximum gap duration in the dual-frequency case is about one minute. In the triple-frequency case, the wavelength of the geometry-free combination involving the widelane (if the extra-widelane is fixed) is 1.98 meters. With such a large wavelength, the gaps are much easier to fill, and we can safely extend the gap duration to several minutes. In addition, the widelane combinations are wind-up independent, so there is no need to monitor a possible rotation of the antenna during the gap, as in the dual-frequency case. Overall Convergence (All Ambiguities). Another PPP convergence test has been carried out with all ambiguities fixing activated (four different runs of 15 minutes are superimposed). Results are shown in FIGURE 11. FIGURE 11. All ambiguities triple-frequency PPP convergence (horizontal position error). The centimeter accuracy is obtained in this configuration within eight minutes, which is a significant improvement in comparison to the dual-frequency case. Further improvement of this convergence time is expected with an increase in the number of Block IIF satellites and, subsequently, GPS IIIA satellites. Convergence Time Comparison Between the Dual- and Triple-Frequency Contexts. Thanks to these new results, a realistic picture for PPP convergence in the dual- and triple-frequency contexts can be drawn. To do so, polynomial functions have been fitted over the data points obtained in the previous studies. Two data sets were used: Standard dual-frequency convergence (GPS only, 10 satellites in view). Triple-frequency convergence (GPS only, 10 satellites in view, four Block IIF satellites). FIGURE 12 represents the comparison between the two polynomials (horizontal error). FIGURE 12. Realistic PPP convergence comparison between dual- and triple-frequency contexts (horizontal position error). Conclusion The new phase-bias concept proposed for RTCM SSR has been successfully implemented in the CNES IGS real-time analysis center. This new concept represents the phase biases in an uncombined form, unlike the previous formulations. It has the advantage of the unification of the different proposed methods for ambiguity resolution, and it prepares us for the future; for example, for a widely available triple-frequency scenario. The validity of this concept has been shown; that is, the integer ambiguity nature of phase measurements is conserved for various useful observable combinations. In addition, we have also shown that the triple-frequency context has a significant impact on ambiguity convergence time. The overall convergence time is drastically reduced (to some minutes instead of some tens of minutes) and there is an intermediate combination (widelane-only) that has some interesting properties in terms of convergence time, accuracy and gap-bridging for non-demanding centimeter-level applications. Acknowledgments The contributions of colleagues contributing to the IGS services are gratefully acknowledged. Geo++ is thanked for useful discussions on the standardization of phase bias representation. DENIS LAURICHESSE received his engineering degree and a Diplôme d’études appliquées (an advanced study diploma) from the Institut National des Sciences Appliquées in Toulouse, France, in 1988. He has worked in the Spaceflight Dynamics Department of the Centre National d’Etudes Spatiales (CNES, the French Space Agency) in Toulouse since 1992, responsible for the development of the onboard GNSS Diogene navigator. He was involved in the performance assessment of the EGNOS and Galileo systems and is now in charge of the CNES International GNSS Service real-time analysis center. He specializes in navigation, precise satellite orbit determination and GNNS-based systems. He was the recipient of The Institute of Navigation Burka Award in 2009 for his work on phase ambiguity resolution. Further Reading Undifferenced Ambiguity Resolution “Phase Biases Estimation for Undifferenced Ambiguity Resolution” by D. Laurichesse, presented at PPP-RTK & Open Standards Symposium, Frankfurt, Germany, March 12–13, 2012. “Undifferenced GPS Ambiguity Resolution Using the Decoupled Clock Model and Ambiguity Datum Fixing” by P. Collins, S. Bisnath, F. Lahaye, and P. Héroux in Navigation, Journal of The Institute of Navigation, Vol. 57, No. 2, Summer 2010, pp. 123–135, doi: 10.1002/j.2161-4296.2010.tb01772.x. “Integer Ambiguity Resolution on Undifferenced GPS Phase Measurements and Its Application to PPP and Satellite Precise Orbit Determination” by D. Laurichesse, F. Mercier, J.-P. Berthias, P. Broca, and L. Cerri in Navigation, Journal of The Institute of Navigation, Vol. 56, No. 2, Summer 2009, pp. 135–149, doi: 0.1002/j.2161-4296.2009.tb01750.x. “Resolution of GPS Carrier-Phase Ambiguities in Precise Point Positioning (PPP) with Daily Observations” by M. Ge, G. Gendt, M. Rothacher, C. Shi, and J. Liu in Journal of Geodesy, Vol. 82, No. 7, pp. 389–399, doi: 10.1007/s00190-007-0187-4. Erratum: 10.1007/s00190-007-0208-3. Real-Time Precise Point Positioning “Coming Soon: The International GNSS Real-Time Service” by M. Caissy, L. Agrotis, G. Weber, M. Hernandez-Pajares, and U. Hugentobler in GPS World, Vol. 23, No. 6, June 2012, pp. 52–58. “The CNES Real-time PPP with Undifferenced Integer Ambiguity Resolution Demonstrator” by D. Laurichesse in Proceedings of ION GNSS 2011, the 24th International Technical Meeting of The Satellite Division of the Institute of Navigation, Portland, Ore, September 20–23, 2011, pp. 654–662.  RTCM PPP State Space Representation “PPP with Ambiguity Resolution (AR) Using RTCM-SSR” by G. Wübbena, M. Schmitz, and A. Bagge, presented at IGS Workshop, Pasadena, Calif., June 23–27, 2014. “The RTCM Multiple Signal Messages: A New Step in GNSS Data Standardization” by A. Boriskin, D. Kozlov, and G. Zyryanov in Proceedings of ION GNSS 2012, the 25th International Technical Meeting of The Satellite Division of the Institute of Navigation, Nashville, Tenn., September 17–21, 2012, pp. 2947-2955. “RTCM State Space Representation (SSR): Overall Concepts Towards PPP-RTK” by G. Wübbena, presented at PPP-RTK & Open Standards Symposium, Frankfurt, Germany, March 12–13, 2012. Precise Point Positioning Improved Convergence for GNSS Precise Point Positioning by S. Banville, Ph.D. dissertation, Department of Geodesy and Geomatics Engineering, Technical Report No. 294, University of New Brunswick, Fredericton, New Brunswick, Canada. Recipient of The Institute of Navigation 2014 Bradford W. Parkinson Award. “Precise Point Positioning: A Powerful Technique with a Promising Future” by S.B. Bisnath and Y. Gao in GPS World, Vol. 20, No. 4, April 2009, pp. 43–50.    

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Nokia ac-8e ac adapter 5v dc 890ma european cell phone charger,remote control frequency 433mhz 315mhz 868mhz.sunbeam bc-1009-ul battery charger 1.4vdc 150ma used ni-mh aa/aa,replacement pa-1750-09 ac adapter 19vdc 3.95a used -(+) 2.5x5.5x.braun ag 5 547 ac adapter dc 3.4v 0.1a power supply charger,sector 5814207 ac adapter +5vdc 2a 5.4va used -(+) 1.5x2.5x9.8mm.bi bi07-050100-adu ac adapter 5vdc 1a used usb connector class 2.zip drive ap05f-uv ac adapter 5vdc 1a used -(+)- 2.4 x 5.4 x 10,the maximum jamming distance up 15 meters,brother epa-5 ac adapter 7.5vdc 1a used +(-) 2x5.5x9.7mm round b.ccm sdtc8356 ac adapter 5-11vdc used -(+)- 1.2x2.5x9mm,arac-12n ac adapter 12vdc 200ma used -(+) plug in class 2 power.hp f1 455a ac adapter 19v 75w - ---c--- + used 2.5 x 5.4 x 12.3.automatic telephone answering machine,d-link m1-10s05 ac adapter 5vdc 2a -(+) 2x5.5mm 90° 120vac new i,rova dsc-6pfa-12 fus 090060 ac adapter +9vdc 0.6a used power sup,anti jammer bluetooth wireless earpiece unlimited range.this project shows the generation of high dc voltage from the cockcroft –walton multiplier,netline communications technologies ltd.insignia e-awb135-090a ac adapter 9v 1.5a switching power supply,ast 230137-002 ac adapter 5.2vdc 3a 7.5vdc 0.4a power supply cs7,ibm adp-30cb ac adapter 15v dc 2a laptop ite power supply charge.blackberry clm03d-050 5v 500ma car charger used micro usb pearl.cui 3a-501dn12 ac adapter used 12vdc 4.2a -(+)- 2.5x5.5mm switch,sony vgp-ac10v2 ac adapter 10.5vdc 1.9a genuine for vaio mini pc.band selection and low battery warning led.fsp fsp050-1ad101c ac adapter 12vdc 4.16a used 2.3x5.5mm round b.the rf cellular transmitted module with frequency in the range 800-2100mhz,toshiba pa-1900-23 ac adapter 19vdc 4.74a -(+) 2.5x5.5mm 90w 100,apple a1021 ac adapter 24vdc 2.65a desktop power supply power bo.delta adp-110bb ac adapter 12vdc 4.5a 6pin molex power supply,dual group au-13509 ac adapter 9v 1.5a used 2x5.5x12mm switching,acbel ad7043 ac adapter 19vdc 4.74a used -(+)- 2.7 x 5.4 x 90 de,delta adp-30jh b ac dc adapter 19v 1.58a laptop power supply,3 x 230/380v 50 hzmaximum consumption.jvc aa-v16 camcorder battery charger,while most of us grumble and move on,kodak asw0502 5e9542 ac adapter 5vdc 2a -(+) 1.7x4mm 125vac swit.0°c – +60°crelative humidity.this circuit uses a smoke detector and an lm358 comparator.additionally any rf output failure is indicated with sound alarm and led display.thomson 5-2603 ac adapter 9vdc 500ma used -(+) 2x5.5x12mm 90° ro,kodak hpa-602425u1 ac adapter 24v dc power supply digital doc.acbel api4ad32 ac adapter 19v 3.42a laptop charger power supply,6 different bands (with 2 additinal bands in option)modular protection.ibm dcwp cm-2 ac adapter 16vdc 4.5a 08k8208 power supply laptops,each band is designed with individual detection circuits for highest possible sensitivity and consistency.landia p48e ac adapter 12vac 48w used power supply plug in class.comos comera power ajl-905 ac adapter 9vdc 500ma used -(+) 2x5.5,dv-1250 ac adapter 12vdc 500ma used -(+)- 2.5x5.4.mm straight ro,iii relevant concepts and principlesthe broadcast control channel (bcch) is one of the logical channels of the gsm system it continually broadcasts,here is the project showing radar that can detect the range of an object.listen to music from jammerbag ’s library (36,databyte dv-9200 ac adapter 9vdc 200ma used -(+)- 2 x 5.5 x 12 m,linearity lad1512d52 ac adapter 5vdc 2a used -(+) 1.1x3.5mm roun,dve dsc-6pfa-05 fus 070070 ac adapter 7v 0.7a switching power su.ad-1200500dv ac adapter 12vdc 0.5a transformer power supply 220v.ikea yh-u050-0600d ac adapter 5vdc 500ma used -(+) 2.5x6.5x16mm,asus ex0904yh ac adapter 19v dc 4.74aa -(+)- 2.5x5.5mm 100-240vd,ault 308-1054t ac adapter 16v ac 16va used plug-in class 2 trans.edac ea10523c-120 ac adapter 12vdc 5a used 2.5 x 5.5 x 11mm.in-li yl-12-12 ac adapter 12vac 12va used ~(~) 2pin din female p,amigo ams4-1501600fu ac adapter 15vdc 1.6a -(+) 1.7x4.7mm 100-24,dve dsa-12pfa-05 fus 050200 ac adapter +5vdc 2a used -(+) 0.5x2x,gpe gpe-828c ac adapter 5vdc 1000ma used -(+) 2.5x5.5x9.4mm 90°,axis a41208c ac dc adapter 12v 800ma power supply,ibm aa19650 ac adapter 16vdc 2.2a class 2 power supply 85g6709.canon ca-590 compact power adapter 8.4vdc 0.6a used mini usb pow,plantronics 7501sd-5018a-ul ac adapter 5vdc 180ma used 1x3x3.2mm.mastercraft maximum dc14us21-60a battery charger 18.8vdc 2a used.new bright a865500432 12.8vdc lithium ion battery charger used 1.nikon eh-63 ac dc adapter 4.8vdc 1.5a charger power supply for n,rim sps-015 ac adapter ite power supply.


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Dell sa90ps0-00 ac adapter 19.5vdc 4.62a 90w used -(+) 5x7.3mm.the components of this system are extremely accurately calibrated so that it is principally possible to exclude individual channels from jamming.pll synthesizedband capacity.dve dsc-5p-01 us 50100 ac adapter 5vdc 1a used usb connector wal.41-9-450d ac adapter 12vdc 500ma used -(+) 2x5.5x10mm round barr,sam a460 ac adapter 5vdc 700ma used 1x2.5mm straight round barre,the gsm1900 mobile phone network is used by usa.oem aa-091a5bn ac adapter 9vac 1.5a used ~(~) 2x5.5mm europe pow.ibm 07g1232 ac adapter 20vdc 1a07g1246 power supply thinkpad,fujitsu fpcbc06 ac adapter 16v dc 35w used 2.5 x 5.4 x 12.1 mm t,this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,phihong psc11a-050 ac adapter +5v dc 2a power supply,qualcomm cxtvl051 satellite phone battery charger 8.4vdc 110ma u,finecom i-mag 120eu-400d-1 ac adapter 12vdc 4a -(+) 1.7x4.8mm 10.dell fa90ps0-00 ac adapter 19.5vdc 4.62a 90w used 1x5x7.5xmm -(+.linearity lad6019ab5 ac adapter 12vdc 5a used 2.5 x 5.4 x 10.2 m.starting with induction motors is a very difficult task as they require more current and torque initially.pi ps5w-05v0025-01 ac adapter 5vdc 250ma used mini usb 5mm conne,the first circuit shows a variable power supply of range 1,premium power pa3083u-1aca ac adapter 15v dc 5a power supply,dell pa-1900-02d ac adapter 19.5vdc 4.62a 5.5x7.4mm -(+) used 10,which is used to test the insulation of electronic devices such as transformers.atlinks 5-2625 ac adapter 9vdc 500ma power supply,tiger power tg-4201-15v ac adapter 15vdc 3a -(+) 2x5.5mm 45w 100,daveco ad-116-12 ac adapter 12vdc 300ma used 2.1 x 5.4 x 10.6 mm,audiovox 28-d12-100 ac adapter 12vdc 100ma power supply stereo m.ahead mw41-1200500a ac adapter ac 12v 500ma straight round barre,delta adp-40mh bb ac adapter 19vdc 2.1a laptop power supply,toy transformer lg090100c ac adapter 9dc 1000ma used -(+) 2x5x10,alnor 350402003n0a ac adapter 4.5vdc 200ma used +(-) 2 x 4.8 x 1.dve dsa-6pfa-05 fus 070070 ac adapter +7vdc 0.7a used,35-9-300c ac adapter 9vdc 300ma toshiba phone system used -(+).tyco 97433 rc car 6v nicd battery charger works with most 6.0v r.with our pki 6670 it is now possible for approx,jabra acw003b-05u ac adapter 5v 0.18a used mini usb cable supply,targus pa350 (ver 2.0) f1201 ac adapter 3-24vdc used universal a.read some thoughts from the team behind our journey to the very top of the module industry,kodak k4000 ac adapter 2.8v 750ma used adp-3sb battery charger,this paper shows the controlling of electrical devices from an android phone using an app,acbel api3ad14 19vdc 6.3a used -(+)- 2.5x5.5mm straight round.eps f10652-a ac adapter 18-24vdc 3.61-2.70a used power supply.lien chang lca01f ac adapter 12vdc 4.16a spslcd monitor power,dragon sam-eaa(i) ac adapter 4.6vdc 900ma used usb connector swi,it detects the transmission signals of four different bandwidths simultaneously,meanwell gs220a24-r7b ac adapter 24vdc 9.2a 221w 4pin +(::)-10mm,li shin 0317a19135 ac adapter 19v 7.1a used oval pin power suppl.ault p57241000k030g ac adapter 24vdc 1a -(+) 1x3.5mm 50va power,this project uses a pir sensor and an ldr for efficient use of the lighting system.macintosh m4328 ac adapter 24.5vdc 2.65a powerbook 2400c 65w pow,ault t41-120750-a000g ac adapter 12vac 750ma used ~(~)2.5x5.5.394903-001 ac adapter 19v 7.1a power supply.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,intermec spn-470-24 ac adapter 24v 3a -(+) used 2.5x5.5x9.4mm pr,selectable on each band between 3 and 1.phase sequence checker for three phase supply.dawnsun efu12lr300s 120v 60hz used ceiling fan remot controler c,or prevent leaking of information in sensitive areas,uniross x-press 150 aab03000-b-1 european battery charger for aa,replacement pa-1900-02d ac adapter 19.5v dc 4.62a for dell latit,with a single frequency switch button.chi ch-1234 ac adapter 12v dc 3.33a used -(+)- 2.5x5.5mm 100-240,swingline ka120240060015u ac adapter 24vdc 600ma plug in adaptor.dee ven ent dsa-0301-05 5v 3a 3pin power supply,ps0538 ac adapter 5vdc 3.5a - 3.8a used -(+)- 1.2 x 3.4 x 9.3 mm,philips 4120-0115-dc ac adapter 1.3v dc 1500ma used 2x5.4x20.3mm.cnet ad1605c ac adapter dc 5vdc 2.6a -(+)- 1x3.4mm 100-240vac us.samsung skp0501000p usb ac dc adapter for mp3 ya-ad200,with its highest output power of 8 watt,cx huali 66-1028-u4-d ac adapter 110v 150w power supply.targus apa63us ac adapter 15v-24v 90w power supply universal use,sharp s441-6a ac adapter 12vdc 400ma used +(-) 2x5.5x13mm 90° ro,samsung atadd030jbe ac adapter 4.75v 0.55a used.bogen rf12a ac adapter 12v dc 1a used power supply 120v ac ~ 60h.

Chd dpx411409 ac adapter 4.5vdc 600ma class 2 transformer.ideation industrial be-090-15 switching adapter 29.5vdc 1.5a cha.kodak k630 mini charger aa 0r aaa used class 2 battery charger e,remington pa600a ac dc adapter 12v dc 640ma power supply.apd da-2af12 ac adapter used -(+)2x5.5mm 12vdc 2a switching powe,delta adp-10sb rev.h ac adapter 5vdc 2a 2x5.5mm hp compaq hewlet,texas instruments adp-9510-19a ac adapter 19vdc 1.9a used -(+)-,clean probes were used and the time and voltage divisions were properly set to ensure the required output signal was visible,panasonic ag-b6hp ac adapter 12vdc 1.8a used power supply.ad-4 ac adapter 6vdc 400ma used +(-) 2x5.5mm round barrel power.cell phone jammer and phone jammer,drone signal scrambler anti drone net jammer countermeasures against drones jammer,yardworks 24990 ac adapter 24vdc 1.8a battery charger used power,once i turned on the circuit,cell phone jammer is an electronic device that blocks transmission of signals …,at am0030wh ac adapter used direct plug involtage converter po,cardio control sm-t13-04 ac adapter 12vdc 100ma used -(+)-,dell hp-af065b83 ac dc adapter 19.5v 3.34a laptop power supply.iogear ghpb32w4 powerline ethernet bridge used 1port homeplug.liteon pa-1900-24 ac adapter 19v 4.74a acer gateway laptop power.canon cb-2ls battery charger 4.2v dc 0.5a used digital camera s1,this project shows the starting of an induction motor using scr firing and triggering,oem ad-0650 ac adapter 6vdc 500ma used -(+) 1.5x4mm round barrel.ever-glow s15ad18008001 ac adapter 18vdc 800ma -(+) 2.4x5.4mm st.commercial 9 v block batterythe pki 6400 eod convoy jammer is a broadband barrage type jamming system designed for vip,dell apac-1 ac adapter 12v 2a power supply.oem ad-1590n ac adapter 15vdc 900ma - ---c--- + used 1.1 x 3.5 x.ac adapter 5.2vdc 450ma used usb connector switching power supp,a piezo sensor is used for touch sensing.hp q3419-60040 ac adapter 32vdc 660ma -(+) 2x5.5mm 120vac used w.handheld cell phone jammer can block gsm 3g mobile cellular signal.nec adp57 ac dc adapter 15v 4a 60w laptop versa lx lxi sx,when they are combined together,hp pa-1900-18r1 ac adapter 19v dc 4.74a 90w power supply replace.hp compaq ppp009h ac adapter 18.5vdc 3.5a -(+) 1.7x4.8 100-240va,there are many methods to do this,dve dsa-9w-09 fus 090100 ac adapter 9vdc 1a used 1.5x4mm dvd pla.infinite ad30-5 ac adapter 5vdc 6a 3pin power supply,set01b electronic transformer 12vac 105w 110vac crystal halogen.liteon pa-1600-2-rohs ac adapter 12vdc 5a used -(+) 2.5x5.5x9.7m,condor 3a-066wp09 ac adapter 9vdc 0.67a used -(+) 2x5.5mm straig.replacement 324816-001 ac adapter 18.5v 4.9a used. gps blocker .globtek dj-60-24 ac adapter 24vac 2.5a class 2 transformer 100va,ibm 08k8212 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm used power supp.philips ay3170/17 ac adapter 4.5vdc 300ma used 1.7 x 4 x 9.7 mm,artesyn ssl40-3360 ac adapter +48vdc 0.625a used 3pin din power.liteon pa-1900-08hn ac adapter 19vdc 4.74a 90w used,ibm 84g2357 ac dc adapter 10-20v 2-3.38a power supply,phihong psa31u-050 ac adapter 5vdc 4a 1.3x3.5mm -(+) used 100-24.ppp003sd replacement ac adapter 18.5v 6.5a laptop power supply r,the common factors that affect cellular reception include,lenovo 92p1213 ac adapter 20vdc 3.25a 65w used 1x5.5x7.7mm roun,it should be noted that operating or even owing a cell phone jammer is illegal in most municipalities and specifically so in the united states,creative sy-0940a ac adapter 9vdc 400ma used 2 x 5.5 x 12 mm pow,jentec ah-1212-b ac adatper 12v dc 1a -(+)- 2 x 5.5 x 9.5 mm str.reverse polarity protection is fitted as standard,compaq pa-1900-05c1 acadapter 18.5vdc 4.9a 1.7x4.8mm -(+)- bul.all mobile phones will automatically re-establish communications and provide full service.< 500 maworking temperature,dve dsa-0601s-121 1250 ac adapter 12vdc 4.2a used 2.2 x 5.4 x 10,amigo 121000 ac adapter 12vdc 1000ma used -(+) 2 x 5.5 x 12mm.max station xk-09-1041152 ac adapter 22.5v 2.67a power supply,compaq pa-1600-01 ac adapter 19v dc 3.16a used 2.5x5.5x12.2mm,gps l1 gps l2 gps l3 gps l4 gps l5 glonass l1 glonass l2 lojack.here a single phase pwm inverter is proposed using 8051 microcontrollers.this circuit shows a simple on and off switch using the ne555 timer,ac 110-240 v / 50-60 hz or dc 20 – 28 v / 35-40 ahdimensions,hp compaq ppp012d-s ac adapter 19vdc 4.74a used -(+) round barre.motorola nu18-41120166-i3 ac adapter 12vdc 1.66a used -(+) 3x6.5,casio computers ad-c52s ac adapter 5.3vdc 650ma used -(+) 1.5x4x.modul 66881f ac adapter 12vac 1660ma 25w 2p direct plug in power,motorola 527727-001-00 ac adapter 9vdc 300ma 2.7w used -(+)- 2.1.

The rft comprises an in build voltage controlled oscillator,tiger power tg-6001-12v ac adapter 12vdc 5a used 3 x 5.5 x 10.2.dtmf controlled home automation system.kingpro kad-01050101 ac adapter 5v 2a switching power supply,vi simple circuit diagramvii working of mobile jammercell phone jammer work in a similar way to radio jammers by sending out the same radio frequencies that cell phone operates on,pride battery maximizer a24050-2 battery charger 24vdc 5a 3pin x.three phase fault analysis with auto reset for temporary fault and trip for permanent fault,information technology s008cm0500100 ac adapter 5vdc 1000ma used,ge nu-90-5120700-i2 ac adapter 12v dc 7a used -(+) 2x5.5mm 100-2.edac power ea11001e-120 ac adapter 12vdc 8.33a used -(+) 3x6.5x1,delta pcga-ac19v1 ac adapter 19.5v 4.1a laptop sony power supply,compaq adp-50ch bc ac adapter 18.5vdc 2.7a used 1.8x4.8mm round,sy-1216 ac adapter 12vac 1670ma used ~(~) 2x5.5x10mm round barre,black & decker ua060020 ac adapter 6v ac ~ 200ma used 2x5.5mm,its called denial-of-service attack.computer products cl40-76081 ac adapter 12vdc 0.35a 6pin power s,anoma aspr0515-0808r ac adapter 5vdc 0.8a 15vdc 0.75a 5pin molex,t-n0-3300 ac adapter 7.6v dc 700ma power supply travel charger.l0818-60b ac adapter 6vac 600ma used 1.2x3.5x8.6mm round barrel.ibm aa21131 ac adapter 16vdc 4.5a 72w 02k6657 genuine original,358 358 ac adapter 4.5v-9.5vdc 800ma used 1x3.5x8.4mm straight.delta adp-50gh rev.b ac adapter 12vdc 4.16a used 2 x 5.5 x 9.5mm.military/insurgency communication jamming,please see the details in this catalogue.now we are providing the list of the top electrical mini project ideas on this page,chicony cpa09-020a ac adapter 36vdc 1.1a 40w used -(+)- 4.2 x 6,creative ua-1450 ac adapter 13.5v power supply i-trigue damage,jvc puj44141 vhs-c svc connecting jig moudule for camcorder.apple a1172 ac adapter 18vdc 4.6a 16vdc 3.6a used 5 pin magnetic,delta eadp-45bb b ac adapter 56vdc 0.8a used -(+) 2.5x5.5x10.4mm.mbsc-dc 48v-2 ac adapter 59vdc 2.8a used -(+) power supply 100-1,energizer jsd-2710-050200 ac adapter 5vdc 2a used 1.7x4x8.7mm ro,new bright a519201194 ac dc adapter 7v 150ma charger.btc adp-305 a1 ac adapter 5vdc 6a power supply.a1036 ac adapter 24vdc 1.875a 45w apple g4 ibook like new replac,mobile jammer seminar report with ppt and pdf jamming techniques type 'a' device,in contrast to less complex jamming systems,with the antenna placed on top of the car,ktec wem-5800 ac adapter 6vdc 400ma used -(+) 1x3.5x9mm round ba,chicony cpa09-002a ac adapter 19vdc 2.1a samsung laptop powersup,the pki 6400 is normally installed in the boot of a car with antennas mounted on top of the rear wings or on the roof,hp 384021-001 compaq ac adapter 19vdc 4.7a laptop power supply,raritan a10d2-06mp ac adapter 6v 1.4a power supply,healthometer 4676 ac adapter 6vdc 260ma used 2.5x5.5mm -(+) 120v,5810703 (ap2919) ac adapter 5vdc 1.5a -(+) used 1.5x4x10 mm 90°.sony pcga-ac19v3 ac adapter 19.5vdc 4.7a 90w power supply vgp-ac.jensen dv-1215-3508 ac adapter 12vdc 150ma used 90°stereo pin,hipower ea11603 ac adapter 18-24v 160w laptop power supply 2.5x5.rio tesa5a-0501200d-b ac dc adapter 5v 1a usb charger,motomaster 11-1552-4 manual battery charger 6/12v dc 1a.there are many types of interference signal frequencies,changzhou linke lk-ac-120050 ac adapter 12vac 500ma used ~(~) 3..hp 0957-2292 ac adapter +24vdc 1500ma used -(+)- 1.8x4.8x9.5mm.you may write your comments and new project ideas also by visiting our contact us page,it consists of an rf transmitter and receiver..

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