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Signal Characteristics of Civil GPS Jammers By Ryan H. Mitch, Ryan C. Dougherty, Mark L. Psiaki, Steven P. Powell, Brady W. O’Hanlon, Jahshan A. Bhatti, and Todd E. Humphreys GPS jamming is a continuing threat. A detailed understanding of how the available jammers work is necessary to judge their effectiveness and limitations. A team of researchers from Cornell University and the University of Texas at Austin reports on their analyses of the signal properties of 18 commercially available GPS jammers. INNOVATION INSIGHTS by Richard Langley GPS IS AT WAR. It is a major asset for United States and allied military forces in a number of operating theaters around the world in both declared and undeclared conflicts. But GPS is at war on the domestic front, too — at war against a proliferation of jamming equipment being marketed to cause deliberate interference to GPS signals to prevent GPS receivers from computing positions to be locally stored or relayed via tracking networks. There have been many notable examples of deliberate jamming of GPS receivers. Many more likely go undetected each day. In 2009, outages of a Federal Aviation Administration reference receiver at Newark Liberty International Airport close to the New Jersey Turnpike were traced to a $33, 200 milliwatt GPS jammer in a truck that passed the airport each day. The driver was reportedly arrested and charged. In July 2010, two truck thieves in Britain were jailed for 16 years. They used GPS jammers to prevent the trucks from being tracked after the thefts. And in Germany, some truck drivers have been using jammers to evade the country’s GPS-based road-toll system. The U.S. and some foreign governments have enacted laws to prohibit the importation, marketing, sale or operation of these so-called personal privacy devices. Nevertheless, a certain number of jammers are in the hands of individuals around the world and they continue to be available from manufacturers and suppliers in certain countries. So, GPS jamming is a continuing threat both at home and abroad and a detailed understanding of how the available jammers work is necessary to judge their effectiveness and limitations. This information will also help in developing countermeasures that could be incorporated into GPS receivers to limit the impact of jammers. Jammers constitute an enemy force, and as the Chinese General Sun Tzu stated in the Art of War more than 2,000 years ago, battles will be won by knowing your enemy. In the last verse of Chapter Three, he states: So it is said that if you know your enemies and know yourself, you can win a hundred battles without a single loss. If you only know yourself, but not your opponent, you may win or may lose. If you know neither yourself nor your enemy, you will always endanger yourself. In this month’s column, a team of researchers from Cornell University and the University of Texas at Austin reports on their analyses of the signal properties of 18 commercially available GPS jammers. The enemy has been exposed. The Global Positioning System has become increasingly incorporated into civilian infrastructure. The increase in GPS-integrated systems has caused a proportional increase in the vulnerability of these systems to jamming and interference. The interests of individuals or groups willing to break the law may be served by interfering with the normal operation of GPS-enabled systems. As a result, in recent years many GPS jamming devices have become available for purchase over the Internet. These relatively cheap devices, some costing less than an inexpensive GPS receiver, pose a significant risk to the normal operation of many systems reliant on GPS. Many types of intentional radio frequency (RF) interference exist, including tones, swept waveforms, pulses, narrowband noise, and broadband noise. There are a number of methods for mitigating the effects of jamming and interference, and additional methods exist to locate the sources of the interference. Mitigation and location methods can be improved by use of a priori information about the interference source. This article provides such a priori information for a set of jammers and assesses their threats. Its results are based on two tests. The first test records raw RF data from a selection of jammers and analyzes it using fast Fourier transform (FFT) spectral methods. The second test evaluates the effective range of a subset of the GPS jammers using a commercial off-the-shelf (COTS) receiver. The article presents results based on 18 civil GPS jammers. There are other types of GPS jammers for sale that were not tested. Furthermore, civil jammer behavior and design is likely to evolve over time. In this article, we draw conclusions based on only the jammers that we tested. Overview of Civil GPS Jammers Devices that claim to jam or “block” GPS signals are widely available through a number of websites and online entities. The cost of these devices ranges from a few tens of dollars to several hundred. Their price does not seem to correlate with the claims made by the purveyors of these devices regarding the features and effectiveness of the product in question. Effective ranges from a few meters to several tens of meters are advertised, but the actual effective ranges are significantly greater. Claimed and true power consumptions range from a fraction of a watt to several watts. We grouped the GPS jammers we examined in this article into three categories based on morphology. The first is a group of jammers designed to plug into an automotive 12-volt auxiliary power supply outlet (cigarette lighter socket); this class of jammer is referred to in the remainder of this article as Group 1. The second category contains those jammers that are both powered by an internal rechargeable battery and that have an external antenna connected via an SMA connector; these jammers are referred to as Group 2. The jammers in Group 3 are disguised as cell phones; they have batteries but no external antennas. Figure 1 shows an example of a device from each of Groups 1–3. Figure 1. Three jammers are depicted, from left to right Jammers 1, 5, and 15 from Groups 1, 2, and 3, respectively. All 18 jammers broadcast power at or near the L1 carrier frequency, six broadcast power at or near the L2 carrier frequency, and none broadcast power at or near the L5 carrier frequency. Some of the jammers also broadcast power at frequencies outside of the GPS bands, typically cellular phone or Wi-Fi bands, but those frequencies are outside the scope of this article. Results in this article are for the current power levels broadcast in the GPS L1 and L2 bands, but examination of power levels in non-GPS bands indicate that many of these devices could be easily modified to broadcast much more power in the GPS bands. The jammer antennas have been removed in most of the testing for this article, but their use in a real-world scenario will modify the jammer behavior. The antennas used by Group 1 and Group 2 jammers are loaded monopole antennas, while those used by the Group 3 jammers are electrically short helical antennas that have approximately the same gain pattern as the loaded monopoles. These antennas broadcast linearly polarized radiation, as opposed to the right-hand circular polarization of GPS signals. The polarization mismatch will cause some loss in received power at a right-hand circularly polarized GPS receiver antenna. Jammer Signal Characteristics Test The goal of the first set of tests was to record complex samples of the jamming signals and to derive the jammer characteristics from these data. A two-step procedure was used to collect useful data. The first step used a spectrum analyzer to find the frequency range of the jamming signal near L1 and L2. The second step used this frequency information to set the center frequency of a general-purpose RF digitization and signal storage device with a 12-drive RAID storage array. Offline analyses were then conducted on the recorded data. The test procedure was as follows. For the first two groups, the jammer was placed inside an RF-shielded test enclosure shown in Figure 2, to prevent any signal leakage, and its SMA signal output port was connected to the relevant data collection device using a shielded coaxial cable. The signal had to pass from the inside to the outside of the RF enclosure using the built-in coaxial feed-through. Note, therefore, that no jammer signal radiation occurred for Group 1 and 2 jammers even inside the RF enclosure. The enclosure was used primarily as a precaution. Figure 2. RF-shielded test enclosure. Jammers were operated inside the enclosure to prevent emission of their RF signals. None of the Group 3 jammers had external antennas. Therefore, they were allowed to radiate in the RF enclosure using their internal antennas. To capture the signal, a receiving patch antenna with active amplification was placed in the RF enclosure, and the antenna output was connected to the relevant RF recording device via the enclosure’s coaxial feed-through. The jammer and receiving antenna were separated by about 14 centimeters. The patch antenna field-of-view center was pointed directly at the jammer. The jammer was oriented such that the axis of its helical antenna was pointing perpendicular to the line from the receiving antenna to the jammer. Jammer Signal Characteristics Test Results Although 18 jammers were tested, only a representative subset is discussed here. The signals were analyzed using FFT spectral methods and measurements of in-band power. Figure 3 displays the results of this analysis for a typical jammer from Group 1. The top plot of Figure 3 graphs frequency on the vertical scale versus time on the horizontal scale. The bottom plot graphs power on the vertical scale versus time on the horizontal scale. Each vertical slice of the recorded RF data plot is a single FFT frequency spectrum. It covers 62.5 MHz centered on the L1 band and has a resolution of approximately 1 MHz. The relative power spectral density of each slice is indicated by color. The time axes of both plots span 80 microseconds. Figure 3. Jammer 4 power spectral density versus time, with color indicating relative power (top plot) and power versus time in a 62.5-MHz band centered at the L1 carrier frequency (bottom plot). The upper plot of Figure 3 is clearly that of a linear frequency modulation interspersed with rapid resets — a series of linear chirps. Each sweep takes nine microseconds and spans a range of about 14 MHz. This range includes the civil L1 GPS band. The center frequency is depicted by the horizontal red line in the top plot. The power is about 20 milliwatts and remains fairly constant over the sweep. Three of the Group 1 jammers appeared to be of the same model and one was slightly different. All of them broadcast power only at L1. Despite their similarities in external appearance, the three jammers of the same model exhibited markedly different signal properties. These differences will be presented later in terms of tabulated frequency modulation characteristics and in-band power levels. One of the Group 2 jammers was unusual in two respects, as illustrated in Figure 4. This figure plots the L2 spectrum whose center is indicated by the horizontal red line in the top plot. The first obvious difference from Figure 3 is that the frequency modulation in time is a triangular wave instead of a sawtooth. Additionally, the modulation frequency is very high in comparison to all the other jammers; its period is only about 1 microsecond. Note that the horizontal scale of this figure spans only 8 microseconds, that is, 10 times less than in Figure 3. The other Group 2 jammers tended to broadcast sawtooth frequency modulations as in Figure 3. They all broadcast jamming power at L1. Of course, the jammer depicted in Figure 4 broadcast power at L2 as well. Only one other Group 2 jammer had L2 jamming capability. Two of the jammers suffered from poor design of their L1 frequency modulation schemes: they placed no jamming power closer than 4.6 MHz away from the nominal L1 carrier frequency. Figure 4. Jammer 10 power spectral density versus time (top plot), with resolution of about 3 MHz and color indicating relative power, and power versus time (bottom plot) in a 62.5-MHz band centered at the L2 carrier frequency. Another unusual frequency modulation was encountered in a Group 3 jammer. The L1 results for this jammer are depicted in Figure 5. It seems to show a linear-type frequency modulation distorted by sudden frequency jumps, as seen in the upper plot of the figure. Despite its irregular nature, this waveform maintains its jamming efficacy. Figure 5. Jammer 15 power spectral density versus time, with color indicating relative power (top plot) and power versus time in a 62.5-MHz band centered at the L1 carrier frequency (bottom plot). Note the additional frequency jumps in the sweep pattern. All four jammers in Group 3 broadcast power at L1, L2, and additional frequency bands. Three of the jammers appeared to be of the same model, while a fourth was different. Jammers in this group normally use a standard sawtooth frequency modulation. Figure 5 represents the exception. Additional types of distortion from the nominal sawtooth frequency modulation have been observed in some of the jammers. Discussion of each additional variation has been omitted here for the sake of brevity. See the authors’ companion conference paper, listed in the Further Reading sidebar for more details. Frequency Modulation Periods and Ranges. The frequency modulation characteristics of all 18 jammers are listed in Table 1. The first two columns identify each jammer by group number and jammer number. The sweep period and frequency range for the L1 sweep are shown in the third and fourth columns. The two numbers in the fourth column are the upper and lower bounds of the jamming tone sweep range in megahertz above and below the L1 carrier frequency. For instance, the period between resets of the linear frequency modulation of Jammer 1 is 26 microseconds and the tone sweeps from 25.4 MHz below L1 to 31.3 MHz above L1. The fifth and sixth columns are analogous to the third and fourth columns, but for jamming in the L2 band, with entries only for those jammers that broadcast in this band. The sweep periods were calculated using four contiguous sweeps from near the beginning of each data set and another four sweeps 30 seconds later. The sweep periods exhibited standard deviations of less than 1 microsecond. The reported sweep ranges are the minimum and maximum frequency observed in the same data used to calculate sweep periods. The sweep ranges changed by as much as 2.5 MHz between sweeps. One can make a number of observations based on Table 1. First, as mentioned previously, jammers which appeared to be of the same model exhibited significant variations in sweep behavior. For instance, Jammers 1, 3, and 4 appeared to be of the same models, yet Jammer 1 has a sweep period nearly three times as long as Jammers 3 and 4. It also has a sweep range four times as wide. Second, some individual jammers were exceptional. For example, Jammer 10 has a sweep period nearly 10 times shorter than any other jammer, and its L1 sweep range exceeded the 62.5 MHz bandwidth recorded by the RF sampling equipment. The sweep range of Jammer 16 also exceeded the sampled bandwidth, though its sweep period was not exceptional. Jammers 12 and 13 do not sweep through the L1 carrier frequency, as indicated by the negative signs in the fourth column of Table 1. Jammer 17 suffered from the same problem, but for both L1 and L2. Table 1. Frequency characteristics of GPS jammers. In-Band Jammer Power Levels. The GPS signal is spread over several megahertz by the pseudorandom noise (PRN) codes that modulate the L1 or L2 carrier waves. Different GPS receivers exploit this spreading by processing more or less of the full bandwidth. The RF power of the GPS jamming signal within different bands centered at L1 is an important concern because different receiver RF front-end bandwidths may allow different total amounts of jammer power to pass through them. For example, a C/A-code receiver with a 2-MHz RF front-end bandwidth will pass 10 dB less jammer power than will a 20-MHz bandwidth RF front end of a P(Y)-code receiver if the jammer in question spreads its power evenly over the 20-MHz band centered at the L1 carrier frequency. If the jammer power is concentrated in a 2-MHz range, however, then both receiver front ends will pass equal total jammer power. To determine the power in different bandwidths, the raw data were filtered to pass only the bandwidths of interest. The data were digitally filtered using a finite input response (FIR) equiripple band-pass filter, providing 60 dB of attenuation at 2 MHz past the roll-off frequency. Note that a real GPS receiver will probably not have analog filter frequency roll offs as sharp as those used in our work. Table 2 presents the results of this study. It reports power measurements averaged over 15 milliseconds in three different bandwidths: 2, 20, and 50 MHz, all centered at the nominal L1 or L2 carrier frequency. The table also indicates whether each jammer broadcasts power at frequencies other than the GPS frequencies. No power data is given for the non-GPS frequencies because they are not the focus of this article. A number of observations can be drawn from Table 2. First, there is a large variation in broadcast power among jammers, with Group 2 jammers being on average more powerful. Specifically, Jammer 11 is the most powerful, broadcasting more than a watt in the GPS bands! Second, jammers of the same model broadcast roughly the same amount of power despite the differences in sweep behavior mentioned above. For instance, Jammers 1, 3, and 4 broadcast roughly the same amount of power, and Jammers 15, 17, and 18 do so as well. Third, the poor frequency plans of Jammers 12, 13, and 17 are apparent in the power measurements. These jammers did not sweep a tone through L1 or L2, and effectively no power was measured in the 2-MHz band centered on the L1 or L2 carrier frequencies. Table 2. Jammer power levels in frequency bands of interest. Although not shown in the tables, Jammers 12, 13, and 14 exhibited periodic variations in broadcast power. Their peak-to-peak power varies as a sawtooth wave with period approximately 15 milliseconds and amplitude on the order of 10 percent of the total broadcast power. The measured power values in Table 2 for jammers of Groups 1 and 2 were derived using direct cable connections. Thus, they report the total power into the transmitting antenna. The power received at a GPS receiver’s RF front end will be affected by any antenna inefficiency, the antenna gain pattern, and the space loss, among other effects. In contrast, the power reported for Group 3 jammers includes all of those effects for the given test configuration. Specifically, the receiving antenna picked up only a fraction of the radiated power because the receiving antenna subtended only a fraction of the 4π steradians around the transmitting antenna. Also, the power that was received was boosted by the receiving antenna’s active low-noise amplifier. Finally, the radiation environment inside the RF enclosure is uncertain, and the enclosure constrains the separation of the antennas to be on the order of one wavelength, thereby giving rise to near-field effects. Therefore, the indicated power levels for the Group 3 jammers do not constitute measures of absolute power. The tabulated power levels for Group 3 jammers are included primarily for purposes of comparison within the group. Maximum Effective Range Test The goal of the second set of tests was to determine the effective ranges of the GPS jammers when interfering with a COTS receiver. A constraint on this test was that it could not broadcast harmful radiation to the environment. Ideally, the jammers and a receiver would be taken outside and tested with all antennas attached. However, this type of test would possibly interfere with other equipment and is illegal in the United States. A close approximation to this scenario can be constructed using a high-fidelity simulated GPS signal, a commercial GPS receiver, a GPS jammer in an RF enclosure, and a set of attenuators to simulate various distances. The setup for the second test is shown in the block diagram of Figure 6. Figure 6. Block diagram of the test procedure and equipment used to determine the GPS jammers’ effective ranges. Each range test involved running a GPS jammer inside the RF enclosure, passing its signal through the enclosure’s coaxial feed-through, and electrically combining that signal with a GPS simulator signal. The combined signal was then input to the antenna connector of the COTS GPS receiver. Attenuators were inserted in-line with the GPS jammer before it arrived at the combiner. Using this setup, two tests were conducted. The first test determined the jamming signal attenuation level necessary for continuous tacking. The second test determined the attenuation level necessary to allow the receiver to acquire the simulator signal within five minutes from a cold start. As will be shown in the next section, the resulting attenuation values can be converted into effective ranges of the jammers if one makes certain reasonable assumptions about transmitting and receiving antenna gains and path losses. The simulator power level was set so that the power into the receiver matched that which it would receive from the actual GPS constellation through a typical roof-mounted passive patch antenna. This power level was checked by comparing the resulting C/N0 for all of the visible satellites when using the simulator against typical C/N0 values when using the roof-mounted antenna. Typical levels reported by the receiver were C/N0 = 43 dB-Hz. Maximum Effective Range Results The jamming signal attenuation levels resulting from the two tests are presented in Table 3. These tests were conducted on one jammer from Group 1 and three jammers from Group 2. No jammers from Group 3 were included because of the broadcast power uncertainties discussed in connection with Table 2. The attenuation values by themselves are not very useful, but they can be converted into distance measurements with a number of assumptions. The ratio of received power to transmitted power can be expressed as where Gt is the transmitting antenna gain, Gr is the receiving antenna gain, and the term (λ/(4πr))2 is the path loss for radiation of wavelength λ over the distance r. This equation can be solved for the range, r: The quantity in this formula that equates to the total electrical jammer attenuation produced in each bench-top test is the product of the antenna gains and the ratio of transmitted to received power: Gt Gr(Pt ⁄Pr ). To convert the results in Table 3 into effective ranges, the transmitting and receiving antennas can be assumed to be perfect, lossless, isotropic radiators. In this case, the gain terms, Gt and Gr , are unity. Each measured attenuation value can be converted to the unitless ratio, Pt ⁄Pr , and substituted into the equation for r. Use of this equation at the L1 carrier frequency yields the ranges in Table 4. If the range between the jammer and receiver is less than that listed in the third column of the table, then the jammer will prevent the receiver from tracking and acquiring. If the range is less than that listed in the last column but more than that listed in the third column, the receiver will continue to track but be unable to acquire. The effective ranges are at least an order of magnitude greater than the claims of the jammers’ purveyors. Table 3. Jammer attenuation levels needed to allow COTS GPS receiver acquisition and tracking. Table 4. Ranges of jammer effectiveness against COTS GPS receiver when using lossless isotropic antennas. Distinct scenarios with different antennas can be approximately tested using Table 3 and the range equation. For example, a patch antenna that is oriented perfectly skyward might have 10 dB of attenuation at very low elevation angles, and the jammer might have an additional 3 dB loss due to polarization mismatch. In this scenario, the effective jamming range would be factored down by 10-13/20 = 0.22. In this case, Jammer 11’s tracking interference range would be reduced from 6.1 kilometers to 1.4 kilometers. Additional jammer signal attenuation might occur if the emissions passed through the reduced RF aperture of a vehicle’s body and windows. Such an effect could be incorporated into the range equation to determine a revised effective range. Due to the ignored losses in the real system, it would likely be safe to assume that the effective ranges of the GPS jammers would be no greater than those listed in Table 4. The ranges could potentially be greater if a high-gain receiving antenna were aimed directly at the jamming source, or if the jamming source used a high-gain transmitting antenna aimed at the receiver. None of the jammers tested employed such an antenna. Summary and Conclusions This article has presented the signal properties of 18 commercially available GPS jammers as determined from two types of live experimental tests. The first test examined the frequency structures and power levels of the jammer signals. It showed that all of the jammers used some sort of swept tone method to generate broadband interference. The majority of the jammers used linear chirp signals, all jammed L1, only six jammed L2, and none jammed L5. The sweep period of the jammers is about 9 microseconds on average, and they tend to sweep a range of less than 20 MHz. Some of the jammers’ sweep ranges failed to encompass the target L1 or L2 carrier frequencies. The second test provided an estimate of four of the jammers’ effective ranges when deployed against a typical commercial receiver. An upper bound on the effective ranges was calculated for idealized, lossless, isotropic radiating and receiving antennas with matched polarizations. The weakest of the four jammers affected tracking at a range of about 300 meters and acquisition at about 600 meters, while the strongest affected tracking at a range of about 6 kilometers and acquisition at about 8.5 kilometers. Acknowledgments The authors thank the U.S. Department of Homeland Security for providing interference devices for testing. This article is based on the paper “Signal Characteristics of Civil GPS Jammers” presented at ION GNSS 2011, the 24th International Technical Meeting of the Satellite Division of The Institute of Navigation, Portland, Oregon, September 19–23, 2011, where it received a best-presentation-in-session award. Manufacturers The tests discussed in this article used an Agilent Technologies (www.home.agilent.com) model N1996A spectrum analyzer, a National Instruments PXI-5663 RF vector signal analyzer, a Ramsey Electronics model STE3000B RF shielded test enclosure, an Antcom (www.antcom.com) model 53G1215A-XT-1 patch antenna, and a NovAtel ProPakII-RT2 GPS receiver. Ryan H. Mitch is a graduate student in the Sibley School of Mechanical and Aerospace Engineering at Cornell University, Ithaca, New York. He received his B.S. degree in mechanical engineering from the University of Pittsburgh. Ryan C. Dougherty is a graduate student in the Sibley School. He holds a B.S. degree in aerospace engineering from the University of Southern California. Mark L. Psiaki is a professor in the Sibley School. He received a B.A. degree in physics and M.A. and Ph.D. degrees in mechanical and aerospace engineering from Princeton University. Steven P. Powell is a senior engineer with the GPS and Ionospheric Studies Research Group in the Department of Electrical and Computer Engineering at Cornell University. He has M.S. and B.S. degrees in electrical engineering from Cornell University. Brady W. O’Hanlon is a graduate student in the School of Electrical and Computer Engineering at Cornell University. He received a B.S. degree in electrical and computer engineering from Cornell University. Jahshan A. Bhatti is pursuing a Ph.D. degree in the Department of Aerospace Engineering and Engineering Mechanics at the University of Texas (UT) at Austin, where he also received his M.S. and B.S. degrees. He is a member of the UT Radionavigation Laboratory. Todd E. Humphreys is an assistant professor in the Department of Aerospace Engineering and Engineering Mechanics at UT Austin and Director of the UT Radionavigation Laboratory. He received B.S. and M.S. degrees in electrical and computer engineering from Utah State University and a Ph.D. degree in aerospace engineering from Cornell University. Further Reading • Authors’ Conference Paper “Signal Characteristics of Civil GPS Jammers” by R.H. Mitch, R.C. Dougherty, M.L. Psiaki, S.P. Powell, B.W. O’Hanlon, J.A. Bhatti, and T.E. Humphreys in Proceedings of ION GNSS 2011, the 24th International Technical Meeting of The Satellite Division of the Institute of Navigation, Portland, Oregon, September 19–23, 2011, pp. 1907–1919. • Vulnerability of GPS Vulnerability Assessment of the Transportation Infrastructure Relying on the Global Positioning System – Final Report. John A. Volpe National Transportation Systems Center, Cambridge, Massachusetts, August 29, 2001. • GPS Jamming “Car Jammers: Interference Analysis” by R. Bauernfeind, T. Kraus, D. Dötterböck, B. Eissfeller, E. Löhnert, and E. Wittmann in GPS World, Vol. 22, No. 10, October 2011, pp. 28–35. “GPS Jamming: No Jam Tomorrow” in The Economist, Technology Quarterly Special Section, Vol. 398, Issue 8724, March 12, 2011, pp. 20–21. Modern Communications Jamming Principles and Techniques, 2nd ed., by R.A. Poisel, published by Artech House, Boston, Massachusetts, 2011. “Jamming GPS: Susceptibility of Some Civil GPS Receivers” by B. Forssell and R.B. Olsen in GPS World, Vol. 14, No. 1, January 2003, pp. 54–58. “A Growing Concern: Radiofrequency Interference and GPS” by F. Butsch in GPS World, Vol. 13, No. 10, October 2002, pp. 40–50. “Interference Effects and Mitigation Techniques” by J.J. Spilker Jr. and F.D. Natali, Chapter 20 in Global Positioning System: Theory and Applications, Volume I, published by the American Institute of Aeronautics and Astronautics, Inc., Washington, D.C., 1996, pp. 717–771. • Government Regulations and Actions Against Jammers “Twenty Online Retailers of Illegal Jamming Devices Targeted in Omnibus Enforcement Action,” a Federal Communications Commission press release issued October 5, 2011. “FCC Enforcement Bureau Steps up Education and Enforcement,” a Federal Communications Commission press release issued February 9, 2011. “Cell Jammers, GPS Jammers, and Other Jamming Devices,” Federal Communications Commission Enforcement Advisory No. 2011-04 issued February 9, 2011, for consumers. “Cell Jammers, GPS Jammers, and Other Jamming Devices,” Federal Communications Commission Enforcement Advisory No. 2011-03 issued February 9, 2011, for retailers. • Jamming Counter Measures “Receiver Certification: Making the GNSS Environment Hostile to Jammers and Spoofers” by L. Scott. Presented to the National Space-Based Positioning, Navigation, and Timing (PNT) Advisory Board, 9th Meeting, November 9–10, 2011, Alexandria, Virginia. “The Civilian Battlefield: Protecting GNSS Receivers from Interference and Jamming” by M. Jones in Inside GNSS, Vol. 6, No. 2, March/April 2011, pp. 40–49. “Interference Heads-up: Receiver Techniques for Detecting and Characterizing RFI” by P.W. Ward in GPS World, Vol. 19, No. 6, June 2008, pp. 64–73. “Jamming Protection of GPS Receivers, Part I: Receiver Enhancements” by S. Rounds in GPS World, Vol. 15, No. 1, January 2004, pp. 54–59. “Jamming Protection of GPS Receivers, Part II: Antenna Enhancements” by S. Rounds in GPS World, Vol. 15, No. 2, February 2004, pp. 38–45. “Antijamming and GPS for Critical Military Applications,” by A. Abbott in Crosslink, Vol. 3, No. 2, Summer 2003, pp. 36–41.

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Apple m3365 ac adapter 13.5vdc 1a -(+) 1x3.4x4.8mm tip 120vac 28,additionally any rf output failure is indicated with sound alarm and led display.nokia ac-3n ac adapter cell phone charger 5.0v 350ma asian versi,panasonic re7-25 ac adapter 5vdc 1000ma used 2 hole pin.this circuit shows a simple on and off switch using the ne555 timer,zenith 150-308 ac adapter 16.5vdc 2a used +(-) 2x5.5x9.6mm round.motorola cell phone battery charger used for droid x bh5x mb810,noise circuit was tested while the laboratory fan was operational.dve dsa-12g-12 fus 120120 ac adapter 12vdc 1a used -(+) 90° 2x5..ancon 411503oo3ct ac adapter 15vdc 300ma used -(+) rf antenna co, http://www.bluzzin.net/gps-signal-blockers-c-107.html .toshiba pa2400u ac adapter 18v 1.1a notebook laptop power supply,hp ppp009s ac adapter 18.5v dc 3.5a 65w -(+)- 1.7x4.7mm 100-240v,compaq adp-60pb acadapter 12vdc 5a 4pin 10mm power dinpowers.iogear ghpb32w4 powerline ethernet bridge used 1port homeplug.a piezo sensor is used for touch sensing.now today we will learn all about wifi jammer.yardworks 18v charger class 2 power supply for cordless trimmer,handheld selectable 8 band all cell phone signal jammer &,320 x 680 x 320 mmbroadband jamming system 10 mhz to 1,hp pa-1900-32ht ac adapter 19vdc 4.74a used ppp012l-e.mot pager travel charger ac adapter 8.5v dc 700ma used audio pin.225univ walchgr-b ac adapter 5v 1a universal wall charger cellph.codi a03002 ac adapter 20vac 3.6a used 3 pin square auto/air pow,toshiba pa2484u ac adapter 15vdc 2.7a ite power supply,cyber acoustics md-75350 ac adapter 7.5vdc 350ma power supply.signal jammer is a device that blocks transmission or reception of signals,netgear dsa-12w-05 fus ac adapter 330-10095-01 7.5v 1a power sup.gamestop 5v wii remote conteroller charging dock,ault t48121667a050g ac adapter 12v ac 1667ma 33.5w power supply.yhi 868-1030-i24 ac adapter 24v dc 1.25a -(+) 1.5x4.8mm used 100,dell pa-1650-05d2 ac adapter 19.5vdc 3.34a used 1x5.1x7.3x12.7mm.kyocera txtvl0c01 ac adapter 4.5v 1.5a travel phone charger 2235.transmission of data using power line carrier communication system,nec op-520-4401 ac adapter 11.5v dc 1.7a 13.5v 1.5a 4pin female.ault 3305-000-422e ac adapter 5vdc 0.3a used 2.5 x 5.4 x 10.2mm,hp pa-1900-18r1 ac adapter 19v dc 4.74a 90w power supply replace,cpc can be connected to the telephone lines and appliances can be controlled easily,delta adp-30ar a ac adapter 12vdc 2.5a used 2x5.5x9mm 90°round b,nyko 87000-a50 nintendo wii remote charge station,koss d48-09-1200 ac adapter 9v dc 1200ma used +(-)+ 2x5.4mm 120v.ite 3a-041wu05 ac adapter 5vdc 1a 100-240v 50-60hz 5w charger p,vipesse a0165622 12-24vdc 800ma used battery charger super long,novus dc-401 ac adapter 4.5vdc 100ma used 2.5 x 5.5 x 9.5mm,toshiba sadp-65kb d ac adapter 19v dc 3.43a used 2.5x5.5x11.9mm,but we need the support from the providers for this purpose,a1036 ac adapter 24vdc 1.875a 45w apple g4 ibook like new replac,sony dcc-e345 ac adapter 4.5v/6v 1.5v/3v 1000ma used -(+)-.dve ds-0131f-05 us 13 ac adapter +5v 2.5a used -(+) 1.2x3.5x9.7m.mastercraft maximum dc18us21-60 28vdc 2a class 2 battery charger,qualcomm taaca0101 ac adapter 8.4vdc 400ma used power supply cha.black & decker s036c 5102293-10 ac adapter 5.5vac 130ma used 2.5,sharp uadp-0220cezz ac adapter 13vdc 4.2a 10pin square lcd tv po,usb 2.0 cm102 car charger adapter 5v 700ma new for ipod iphone m,tec b-211-chg-qq ac adapter 8.4vdc 1.8a battery charger.yhi yc-1015xxx ac adapter 15vdc 1a - ---c--- + used 2.2 x 5.5 x,delta adp-65jh db ac adapter 19v 3.42a acer travelmate laptop po,ps5185a ac adapter 5v 550ma switching power supply for cellphone.braun 4729 ac adapter 250vac ~ 2.5a 2w class 2 power supply.it’s really two circuits – a transmitter and a noise generator.


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Ultrafire wf-139 rechargeable battery charger new for 3.7v 17500,cobra ga-cl/ga-cs ac adapter 12vdc 100ma -(+) 2x5.5mm power supp,backpack bantam aua-05-1600 ac adapter 5v 1600ma used 1.5 x 4 x,startech usb2sataide usb 2.0 to sata ide adapter,powmax ky-05048s-29 ac adapter 29vdc 1.5a 3pin female uk plug,it is your perfect partner if you want to prevent your conference rooms or rest area from unwished wireless communication.dell pa-12 ac adapter 19.5vdc 3.34a power supply for latitude in.rf 315 mhz 433mhz and other signals.sony vgp-ac19v42 ac adapter 19.5vdc 4.7a used 1x4x6x9.5mm,atlinks usa inc. 5-2509 ac dc adapter 9v 450ma 8w class 2 power,bellsouth sa41-57a ac adapter 9vdc 400ma used -(+) 2x5.5x12mm 90,520-ps12v2a medical power supply 12v 2.5a with awm e89980-a sunf,cobra swd120010021u ac adapter 12vdc 100ma used 2 audio pin,iluv dys062-090080w-1 ac adapter 9vdc 800ma used -(+) 2x5.5x9.7m,pepsi diet caffein- free cola soft drink in bottles,shindengen za12002gn ac adapter 12v 2a ite power supply,because in 3 phases if there any phase reversal it may damage the device completely,ad-1200500dv ac adapter 12vdc 0.5a transformer power supply 220v.gnt ksa-1416u ac adapter 14vdc 1600ma used -(+) 2x5.5x10mm round,modul 66881f ac adapter 12vac 1660ma 25w 2p direct plug in power,accordingly the lights are switched on and off.all mobile phones will indicate no network,motorola r35036060-a1 spn5073a ac adapter used 3.6vdc 600ma,basically it is way by which one can restrict others for using wifi connection,for any further cooperation you are kindly invited to let us know your demand,universal power supply ctcus-5.3-0.4 ac adapter 5.3vdc 400ma use,when the mobile jammer is turned off,ar 35-12-100 ac adapter 12vdc 100ma 4w power supply transmiter,a blackberry phone was used as the target mobile station for the jammer.lf0900d-08 ac adapter 9vdc 200ma used -(+) 2x5.5x10mm round barr.compaq presario ppp005l ac adapter 18.5vdc 2.7a for laptop.replacement ppp003sd ac adapter 19v 3.16a used 2.5 x 5.5 x 12mm,phihong psm11r-120 ac adapter 12v dc 0.84a max new 2x5.5x9.5mm,minolta ac-7 ac-7e ac adapter 3.4vdc 2.5a -(+) 1.5x4mm 100-240va,gf np12-1s0523ac adapter5v dc 2.3a new -(+) 2x5.5x9.4 straig.synchronization channel (sch),apd wa-18g12u ac adapter 12vdc 1.5a -(+)- 2.5x5.5mm 100-240vac u,toshiba pa2440u ac adapter 15vdc 2a laptop power supply.lenovo pa-1900-171 ac adapter 20vdc 4.5a -(+) 5.5x7.9mm tip 100-.sanyo scp-06adt ac adapter 5.4v dc 600ma used phone connector po,li shin lse9901b1260 ac adapter12vdc 5a 60w used 4pin din power,9 v block battery or external adapter,compaq 2932a ac adapter 5vdc 1500ma used 1 x 4 x 9.5mm,air rage wlb-33811-33211-50527 battery quick charger,xiamen keli sw-0209 ac adapter 24vdc 2000ma used -(+)- 2.5x5.5mm,aplha concord dv-1215a ac adapter 12vac,sony ac-l25a ac adapter 8.4vdc 1.7a 3 pin connector charger ac-l,almost 195 million people in the united states had cell- phone service in october 2005.chicony cpa09-020a ac adapter 36vdc 1.1a 40w used -(+)- 4.2 x 6.acbel api3ad01 ac adapter 19vdc 6.3a 3x6.5mm -(+) used power sup,ault cs240pwrsup ac adapter 7.5vdc 260ma used 9.0vac 250ma.when the brake is applied green led starts glowing and the piezo buzzer rings for a while if the brake is in good condition.main business is various types of jammers wholesale and retail.chang zhou tai yu rkdc0450300 ac adapter 4.5vdc 300ma power supp.hp compaq ppp014s ac adapter 18.5vdc 4.9a used 2.5x5.5mm 90° rou,canon battery charger cb-2ls 4.2vdc 0.7a 4046789 battery charger,acbel ap13ad03 ac adapter 19vdc 3.42a power supply laptop api-76,kenwood dc-4 mobile radio charger 12v dc.jt-h090100 ac adapter 9vdc 1a used 2.5x5.5mm straight round barr,acbel api3ad03 ac adapter 19v dc 3.42a toshiba laptop power supp.

680986-53 ac adapter 6.5v 250ma used cradle connector plug-in.hon-kwang hk-c110-a05 ac adapter 5v 0.25a i.t.e supply.from the smallest compact unit in a portable.motorola spn4226a ac adapter 7.8vdc 1a used power supply,ryobi 1400666 charger 14vdc 2a 45w for cordless drill 1400652 ba,frequency scan with automatic jamming,delta sadp-135eb b ac adapter 19vdc 7.1a used 2.5x5.5x11mm power.energizer pc-1wat ac adapter 5v dc 2.1a usb charger wallmount po,wp weihai has050123-k1 ac adapter 12vdc 4.16a used -(+) 2x5.5mm,a potential bombardment would not eliminate such systems.csec csd1300150u-31 ac adapter 13vdc 150ma used -(+)- 2x5.5mm.globetek ad-850-06 ac adapter 12vdc 5a 50w power supply medical.adapter tech std-0502 ac adaptor 5vdc 2a -(+) 2x5.5mm used 100-1,514 ac adapter 5vdc 140ma -(+) used 2.5 x 5.5 x 12mm straight ro,elpac power systems 2180 power supply used +8vdc 4a 32w shielded.hp 0950-3796 ac adapter 19vdc 3160ma adp-60ub notebook hewlett p,people also like using jammers because they give an “out of service” message instead of a “phone is off” message,outputs obtained are speed and electromagnetic torque,please see our fixed jammers page for fixed location cell.1800 mhzparalyses all kind of cellular and portable phones1 w output powerwireless hand-held transmitters are available for the most different applications,poweruon 160023 ac adapter 19vdc 12.2a used 5x7.5x9mm round barr,charger for battery vw-vbg130 panasonic camcorder hdc-sd9pc sdr-.ac adapter 4.5v 9.5v cell phone power supply.finecom ad-6019v replacement ac adapter 19vdc 3.15a 60w samsung,15.2326 ac adapter 12vdc 1000ma -(+) used 2.4 x 5.5 x 8.3.5mm.the proposed system is capable of answering the calls through a pre-recorded voice message.power amplifier and antenna connectors,basler be 25005 001 ac adapter 10vac 12va used 5-pin 9mm mini di,phase sequence checking is very important in the 3 phase supply.kodak vp-09500084-000 ac adapter 36vdc 1.67a used -(+) 6x4.1mm r.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,wang wh-501ec ac adapter 12vac 50w 8.3v 30w used 3 pin power sup,dve dsa-0301-05 ac adapter 5vdc 4a 4pin rectangle connector swit,nec adp-50mb ac adapter 19v 2.64a laptop power supply,delta electronics adp-40sb a ac adapter 16v dc 2.5a used,this sets the time for which the load is to be switched on/off,ault 7ca-604-120-20-12a ac adapter 6v dc 1.2a used 5pin din 13mm,preventing them from receiving signals and ….the present circuit employs a 555 timer.simple mobile jammer circuit diagram cell phone jammer circuit explanation.sunny sys1308-2415-w2 ac adapter 15vdc 1a -(+) used 2.3x5.4mm st.bose psa05r-150 bo ac adapter 15vdc 0.33a used -(+)- 2x5.5mm str.insignia ns-pltpsp battery box charger 6vdc 4aaa dc jack 5v 500m,lenovo 92p1213 ac adapter 20vdc 3.25a 65w used 1x5.5x7.7mm roun.this project shows the control of that ac power applied to the devices,hi capacity san0902n01 ac adapter 15-20v 5a -(+)- 3x6.5mm used 9,this project uses arduino and ultrasonic sensors for calculating the range.rim psm05r-068r dc adapter 6.8v dc 0.5a wall charger ite,morse key or microphonedimensions,ridgid r840091 ac adapter 9.6-18v 4.1a used lithium ion ni-cad r,3com dve dsa-12g-12 fus 120120 ac adapter +12vdc 1a used -(+) 2..canon k30287 ac adapter 16vdc 2a used 1 x 4.5 x 6 x 9.6 mm.computer rooms or any other government and military office.ihomeu150150d51 ac adapter 15vdc 1500ma -(+) 2.1x5.5x10mm roun.apple a1021 ac adapter 24vdc 2.65a desktop power supply power bo.cambridge soundworks tead-66-132500u ac adapter 13.5vdc 2.5a,nok cla-500-20 car charger auto power supply cla 10r-020248.ad35-03006 ac adapter 3vdc 200ma 22w i t e power supply,palmone dv-0555r-1 ac adapter 5.2vdc 500ma ite power supply,long-range portable protection.

Bell phones dv-1220 dc ac adapter 12vdc 200ma power supply,can be adjusted by a dip-switch to low power mode of 0,frost fps-02 ac adapter 9.5vdc 7va used 2 x 5 x 11mm,kodak k620 value charger for aa and aaa size batteries.sony ac-v25b ac adapter 7.5v 1.5a 10v 1.1a charger power supply,the integrated working status indicator gives full information about each band module,therefore the pki 6140 is an indispensable tool to protect government buildings.d-link dir-505a1 ac adapter used shareport mobile companion powe.motorola plm4681a ac adapter 4vdc 350ma used -(+) 0.5x3.2x7.6mm.mastercraft sa41-6a battery carger 7.2vdc used -(+) power supply,palm plm05a-050 ac adapter 5vdc 1a power supply for palm pda do.ac adapter mw35-0900300 9vdc 300ma -(+) 1.5x3.5x8mm 120vac class,dell pa-1470-1 ac adapter 18v 2.6a power supply notebook latitud,cell phone jammer is an electronic device that blocks the transmission of signals between the cell phone and its nearby base station,ab41-060a-100t ac adapter 5vdc 1a.compaq pa-1530-02cv ac adapter 18.5vdc 2.7a used 1.7x5mm round b,control electrical devices from your android phone.pa-1600-07 replacement ac adapter 19vdc 3.42a -(+)- 2.5x5.5mm us,dell hp-af065b83 ow5420 ac adapter 19.5vdc 3.34a 65w laptop powe.the jammer transmits radio signals at specific frequencies to prevent the operation of cellular and portable phones in a non-destructive way,noise generator are used to test signals for measuring noise figure.sceptre ad2524b ac adapter 25w 22.0-27vdc 1.1a used -(+) 2.5x5.5,spi sp036-rac ac adapter 12vdc 3a used 1.8x4.8mm 90° -(+)- 100-2.zip drive ap05f-us ac adapter 5vdc 1a used -(+) 2.5x5.5mm round.sony ac-l15b ac dc adapter 8.4v 1.5a power supply for camcorder.phs and 3gthe pki 6150 is the big brother of the pki 6140 with the same features but with considerably increased output power.motorola htn9000c class 2 radio battery charger used -(+) 18vdc.hipro hp-ol060d03 ac adapter 12vdc 5a used -(+)- 2.5x5.5power su,akii techa25b1-05mb ac adapter +5vdc 5a power supply.creative sy-0940a ac adapter 9vdc 400ma used 2 x 5.5 x 12 mm pow,sima sup-60 universal power adapter 9.5v 1.5a for camcorder.motomaster 11-1552-4 manual battery charger 6/12v dc 1a.ault pw173kb1203b01 ac adapter +12vdc 2.5a used -(+) 2.5x5.5mm m.the designed jammer was successful in jamming the three carriers in india,it is also buried under severe distortion.casio ad-a60024ac adapter 6vdc 240ma used -(+) 2x5.5mm round b,ibm 12j1447 ac adapter 16v dc 2.2a power supply 4pin for thinkpa,.

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