Testing GNSS Receivers with Record and Playback Techniques By David A. Hall Is there a way to perform repeatable tests on GNSS receivers using real signals? This month’s column looks at how to use an RF vector signal analyzer to digitize and record live signals, and then play them back to a GNSS receiver with an RF vector signal generator. INNOVATION INSIGHTS by Richard Langley AS A PROFESSOR, I’m quite familiar with testing — of students, that is. It’s how we check their performance — how well they have mastered the course material. Outside academia, testing is also quite common. We have to pass a driving test before we can get a license. We might have to pass a physical fitness test before starting a job. And manufacturers have to test or stress their products to make sure they are fit for purpose. As David Ogilvy, the father of advertising once quipped, “Never stop testing, and your advertising will never stop improving.” But it’s not just manufacturers who should test products. Consumers, or their representatives, should test products on offer — not only to corroborate (or dispute) manufacturers’ claims but also to compare one manufacturer’s product against another. There’s a whole slew of magazines, television programs, and web resources devoted to testing and comparing everything from laundry detergent to automobiles. And GNSS receivers are no exception. When we conduct tests, we are usually trying to get answers to certain questions — just like those posed to students on their exams. In testing GNSS receivers, what are some appropriate questions? When a receiver is turned on, how long does it take until the position of the receiver is determined? When a weak signal area is encountered, can the receiver still determine its position? If the signal is interrupted and then restored, how long does it take for the receiver to recover and resume calculating its position? And what is the position accuracy under different situations? While we can certainly hook up an antenna to a receiver to get answers to these questions in a certain environment on a certain day at a certain time with certain signals, the scenario cannot be repeated — not exactly. If we tweak a receiver operating parameter, for example, we don’t know for certain whether any observed change is due to the tweaking or a change in the scenario. We could use a radio-frequency (RF) simulator — a device for mimicking the radio signals generated by the satellites. This would allow us to define scenarios, including receiver trajectories, and to replay them as many times as necessary while varying the operating parameters of the receiver. Or we could modify the scenario from run to run. Such test scenarios could include those difficult to carry out with live signals such as determining how a receiver would perform in low Earth orbit. While extremely useful, these are tests with simulated signals. Is there a way to perform repeatable tests on GNSS receivers using real signals? In this month’s column, we learn how to use an RF vector signal analyzer to digitize and record live signals, and then play them back to a GNSS receiver with an RF vector signal generator — a procedure we can repeat as often as we like. While GNSS simulators have long provided the de facto technique for testing GPS receivers, radio frequency (RF) record and playback has emerged as an innovative method to introduce real-world impairments to GNSS receivers. In this article, we will provide a hands-on tutorial on how to test a navigation device using the record and playback technique. The premise of RF record and playback is to capture GNSS signals off the air with a vector signal analyzer (VSA) and then replay them to a receiver with an RF vector signal generator (VSG). With recorded GNSS signals, one is able to introduce a signal that contains natural impairments — instead of an ideal signal — to the GNSS receiver. As a result, one can observe how a receiver will behave in a real-world environment where interference, multipath fading, and other impairments are present. A VSA combines traditional superheterodyne radio receiver technology with high-speed analog-to-digital converters and digital signal processors to perform a variety of measurements on complex modulated signals. It is widely used in the telecommunications industry as a test instrument. Digitized signals can be recorded for future analysis. A VSG reverses the process, taking a digital representation of a complex waveform and, using digital-to-analog converters, generating an appropriately modulated RF signal. Recording GPS or GLONASS signals off the air can be done in a fairly straightforward manner. An RF recording system combines appropriate antennas, amplifiers, and an RF signal recorder (usually a VSA) to capture many hours of continuous RF signal. In such a system, the basic components include the RF front end, the RF signal-acquisition device, and high-volume storage media. A block diagram of a typical recording system is shown in Figure 1. Figure 1. GPS receivers implement cascaded low-noise amplifiers. The RF signal acquisition block includes analog-to- digital conversion (ADC) and digital down conversion (DDC) to select the data of interest. In the figure, the RF front end is designed to condition the GNSS signal in such a way that it can be captured — with maximum dynamic range — by the recording device. The recording device digitizes a given signal bandwidth, and then stores in-phase and quadrature (IQ) waveforms to disk. In general, RF recording devices are designed to tune to a broad range of frequencies and can thereby record many different types of signals. Thus, selecting the signal to record is as simple as setting the center frequency and bandwidth of the recording device. For example, to record the GPS C/A-code L1 signal, the center frequency should be set to 1575.42 MHz. Because each satellite generates the same carrier frequency, one can capture C/A-code signals from all satellites simply by capturing all signals within a 2.046 MHz (twice the code chipping rate) band around the carrier frequency. By contrast, recording GLONASS signals requires slightly different settings. Because the GLONASS constellation uses frequency division multiplexing, every satellite generates the same code, but each pair of antipodal satellites transmits at a unique center frequency. Thus, recording L1 signal information for the entire GLONASS constellation requires a recorder to capture signals that range from 1598.0625 MHz (channel -7) to 1605.375 MHz (channel 6). In order to capture the entire bandwidth of each satellite, a recorder is actually required to capture 1.022 MHz of signal for each carrier (again, twice the code chipping rate). Therefore, the total recording bandwidth is actually 1597.5515 MHz to 1605.886 MHz, a span of 10.3345 MHz. On the RF signal analyzer, one can record GLONASS signals simply by setting the center frequency to 1601.71875 MHz, and the bandwidth to ≥ 10.3345 MHz. Modern RF signal recorders are capable of recording both GPS and GLONASS C/A-code signals on a single wideband recording channel. For example, one of our RF signal analyzers is capable of recording up to 50 MHz of signal bandwidth. With this instrument, one can simultaneously record both GPS and GLONASS by setting the center frequency to 1590.1415 MHz and the bandwidth to ≥ 31.489 MHz. However, while RF recording systems can be used to capture a wide range of GNSS signals including GPS L1/L2/L5, GLONASS L1/L2, Galileo, and others, this article focuses primarily on the GPS C/A-code signal. Setting up the RF Front End The trickiest aspect of recording GPS signals is the selection and configuration of the appropriate antenna and low noise amplifier (LNA). When connecting a typical off-the-shelf GPS passive patch antenna to a signal analyzer, the peak power in the GPS L1 band ranges from -120 to -110 dBm. Because the power level of GPS signals is small, significant amplification is required to ensure that the VSA can capture the full dynamic range of the signal. The simplest method to amplify an off-the-air GPS signal so that it can be captured by an RF signal recorder is the combination of an active GPS antenna and one or more external LNAs. Note that many professional GPS antennas offer the best performance because they combine high element gain with an LNA and even pre-selection filtering, which improves the dynamic range of the RF recorder. With the RF front end appropriately configured, one can verify system performance using a simple spectrum analyzer demonstration panel. The demo panel allows one to visualize the RF spectrum in the GPS L1 band. If all is set up correctly, the C/A-code GPS signal should be visually present on the display. Figure 2 illustrates a screenshot of the spectrum on a virtual spectrum analyzer display. Note that visualizing the GPS signal in the frequency domain with an RF signal recorder (or spectrum analyzer) requires careful attention to settings such as resolution bandwidth and averaging. Because the signal-to-noise ratio (SNR) of the GPS signal is so small, the settings shown in Figure 2 require a narrow resolution bandwidth (10 Hz) and significant averaging (20 averages per measurement record, so a 20-second interval for 1 Hz data). With these settings applied, one can easily visualize a modulated signal above the noise floor with approximately 1 MHz of bandwidth and centered at 1575.42 MHz. This signal is the GPS C/A-code. In Figure 2, the reference level of the signal analyzer was set to -50 dBm to reduce the noise floor of the instrument to the lowest possible level. Note that setting the signal analyzer’s reference level provides a simple mechanism to adjust the front-end attenuation or amplification. In general, RF signal analyzers provide the greatest dynamic range when the reference level of the instrument matches closely with the average power of the signal connected to the front end. In this case, setting the reference level of our signal analyzer to -50 dBm removes all front-end attenuation, giving the analyzer a more optimal noise figure for signal recording. Figure 2. GPS is visible in the spectrum only if a narrow resolution bandwidth is used. This spectrum was obtained with a center frequency of 1575.42 MHz, a frequency span of 4 MHz, a resolution bandwidth of 10 Hz, root-mean-square averaging with 20 averages, and a reference level of 250 dBm. Hardware Connections With the reference level appropriately set, it is important to properly configure the RF front end of the recording device. As previously mentioned, one can achieve the best RF recording results by using an active GPS antenna. The active antenna used in our experiment utilized a built-in LNA to provide up to 30 dB of gain with a 1.5 dB noise figure. (Recall that the noise figure is the difference in dB between the noise output of a device and the noise output of an “ideal” device with the same gain and bandwidth when it is connected to sources at the standard noise temperature — usually 290 K.) However, the LNA must be powered by supplying a DC bias to the RF connection. While there are several methods to supply the DC bias, we will look at two of the easiest methods. Method 1: Active Antenna Powered by GPS Receiver. The first method to power an active antenna is with a bias tee or DC power injector. Using this three-port component, a DC voltage (3.3 V in this case) is fed to its DC port, which applies the appropriate DC offset to the active antenna connected to the RF-in port while blocking it on the RF-out port. The device gets its name from the fact that the three ports are often arranged in the shape of a “T.” Note that the precise DC voltage one should apply depends on the DC power requirements of the active antenna. A diagram illustrating the connections is shown in Figure 3. Observe in Figure 3 that one can use off-the-shelf hardware such as a programmable DC power supply to supply the DC bias signal. Also, one can use a generic off-the-shelf bias tee as long as it has bandwidth up to 1.58 GHz. Figure 3. This set-up shows the use of a DC bias tee to power an active GPS antenna. Method 2: Active GPS Antenna Powered by Receiver. A second method of powering the active GPS antenna is with the receiver itself. Most off-the-shelf GPS receivers use a single port to power and receive signals from an active GPS antenna, and this port is already biased with an appropriate DC voltage. Combining an active GPS receiver, a power splitter, and a DC blocker, one can power an active LNA and simply record essentially the same signal as that observed by the GPS receiver. A diagram of the appropriate connections is shown in Figure 4. Some splitters incorporate a DC block on all but one of the output ports. As Figure 4 illustrates, the DC bias from the GPS receiver is used to power the LNA. This method is particularly useful for drive tests because one can observe the receiver’s characteristics, such as velocity and dilution of precision, while recording. Figure 4. With a DC blocker, one can record and analyze the same GPS signals being tracked by a GPS receiver. Selecting the Right LNA Recording GPS signals with generic RF signal recorders is possible largely because external LNAs can be used to reduce the effective noise floor of the receiver. Today, one can find off-the-shelf spectrum analyzers with noise figures ranging from 15 dB to 20 dB. One of our analyzers, for example, has a 15 dB noise figure while applying up to 60 dB of gain. By applying external amplification to the front of an RF signal analyzer, however, one can substantially reduce the noise figure of the RF recording system. To calculate the total noise that will be added to the recorded GPS signal, one must calculate the noise figure for the entire RF front end. As a matter of principle, the noise figure of the entire system is always dominated by the first amplifier in the system. Thus, careful selection of the first and second stage LNAs is crucial for a successful signal recording. We can calculate the noise figure of the RF recording system by using the Friis formula for noise figure, named for engineer Harald Friis, a Danish-American radio engineer who worked at Bell Telephone Laboratories. To use this formula, first convert the gain and noise figure of each component to its linear equivalent; the latter is called the “noise factor.” For cascaded systems such as our RF recording system, the Friis formula provides us with the noise factor of the entire system: (1) Note that both noise factor (nf) and gain (g) are shown in lowercase to distinguish them as linear measures rather than logarithmic measures. The conversion from linear to logarithmic gain and noise figure (and vice v ersa) is shown in the following equations: An active GPS antenna using a built-in LNA typically provides 30 dB of gain while introducing a noise figure that is typically on the order of 1.5 dB. The second part of the recording instrumentation provides 30 dB of additional gain as well. Though its noise figure is higher (5 dB), the second amplifier actually introduces very little noise into the system. As an academic exercise, one can use the Friis formula to calculate the noise factor for the entire RF front end of the recording instrumentation. Gain and noise figure values are shown in Table 1. Table 1. Noise figures and factors of the first two components of the RF front end. According to the calculations above, one can determine the overall noise factor for the receiver: (6) To convert noise factor into a noise figure (in dB), apply Equation 2, which yields the following results: (7) As Equation 7 illustrates, the noise figure of the first LNA (1.5 dB) dominates the noise figure of the entire RF recording system. Thus, with the VSA configured such that the noise floor of the instrument is less than that of the input stimulus, one’s recording introduces only 1.507 dB of noise to the off-the-air signal. Saving Data to Disk Each GNSS produces slightly varying requirements for an RF recorder’s signal bandwidth and center frequency. For the GPS C/A-codes, the essential requirement is to record 2.046 MHz of RF bandwidth at a center frequency of 1575.42 MHz. In the tests described here, we set the IQ sample rate of our RF recorder at 5 megasamples per second (Ms/s). Since each 16-bit I and Q sample is 32 bits (or 4 bytes each), the actual recording data rate is 20 megabytes per second (MB/s) to ensure the entire bandwidth was captured. Capturing more than 4 MHz of bandwidth is sufficient to record the 2.046 MHz C/A-code signals. Because one can achieve data rates of 20 MB/s or more with standard PXI controller hard drives (PXI is the open, PC-based platform for test, measurement, and control), one does not need to use an external redundant array of independent disks (RAID) volume to stream GPS signals to disk when using a PXI recording system. In general, data rates exceeding 20 MB/s require the use of an external RAID volume. External RAID systems are capable of storing more than 600 MB/s of data and can be used to support wide bandwidth channels or even multi-channel recording applications. For example, the recording system shown in Figure 5 uses an external RAID volume for high-speed signal recording. This system combines PXI RF signal generators and analyzers with external amplifiers and filter banks for a ready-to-use GNSS record and playback solution. Figure 5. Two-channel record and playback system from Averna. In our tests, we decided to use a 320 GB USB drive for better portability. With a disk speed of 5400 revolutions per minute, we were able to benchmark it ahead of time and observed that we were able to achieve read and write speeds exceeding 25 MB/s. Thus, we were easily able to use this disk drive and still record IQ samples at 5 MS/s (20 MB/s) when recording off-the-air signals. With the existing hard-drive setup, we could record more than 4 hours of continuous IQ signal. Note that capturing longer recordings simply requires a larger hard disk. By using a 2 terabyte RAID volume (the largest addressable disk size in the Windows XP operating system), we can extend our recording time to 25 hours. With this setup, we could also reduce the IQ sample rate to 2.5 MS/s (still sufficient to capture the GPS C/A-code signals) and extend the recording time to 50 hours. Receiver Performance Once the off-the-air signal of a GNSS band is recorded to disk, it can be re-generated and fed to a receiver using an RF signal generator. With an RF signal generator that is able to reproduce the real-world GNSS signal, engineers are able to test a wide range of receiver characteristics. Because recorded signals contain a rich set of channel impairments such as ionosphere distortion and interference from other transmitters, design engineers often use recorded signals to prototype the baseband processing algorithms on a GNSS receiver. In our case, we used a VSG directly connected to a GPS evaluation board. In the experiments described below, the receiver’s latitude, longitude, and velocity were tracked over time. Data was read from the receiver using a serial port, which read NMEA 0183 sentences at a rate of one per second. NMEA 0183 is a standard protocol developed by the National Marine Electronics Association for communications between marine electronic devices. NMEA 0183 has been adopted by virtually all GPS receiver manufacturers. In our LabVIEW graphical development environment, one can parse all sentences to return satellite and position-fix information. For practical testing purposes, GPS dilution of precision and active satellites (GSA), GPS satellites in view (GSV), course over ground and ground speed (VTG), and GPS fix data (GGA) sentences are the most useful. More specifically, one can use information from the GSA sentence to determine whether the receiver has achieved a position fix and is used in time-to-first-fix measurements. When performing sensitivity measurements in this example, the GSV sentence was used to return carrier-to-noise-density ratios (C/N0) for each satellite being tracked. In addition, the VTG sentence allows us to observe the velocity of the receiver. Finally, the GGA sentence provides the receiver’s precise position by returning latitude and longitude information. See the references in Further Reading for in-depth information on the NMEA 0183 protocol. Using the receiver’s reported latitude and longitude information, we are able to test its ability to report a repeatable position when the recorded signal is played back to the receiver. In this experiment, we tracked the receiver position over 10 minutes. For the best results, the command interface of the receiver should be tightly synchronized with the start trigger of the RF signal generator. The results in Figure 6 show that the RF vector signal generator in this experiment was synchronized with the GPS receiver by using the data line of the serial communications (COM) port (RxD, pin 2) as a start trigger. Using this synchronization method, the vector signal generator and GPS receiver were synchronized to within one clock cycle of the VSG’s arbitrary waveform generator (100 MS/s). Thus, the maximum skew should be limited to 10 microseconds. Given our receiver’s maximum velocity of 15 meters per second (our maximum speed on the drive test), we can determine that the maximum error induced by clock offset of the signal generator is 10 microseconds x 15 meters per second, or 0.15 millimeters. Using the configuration described above, one is able to report the receiver’s latitude and longitude over time, as shown in Figure 6. Figure 6A. Receiver latitude over a four-minute span. Figure 6B. Receiver longitude over a four-minute span. As the data from Figure 6 illustrate, a recorded test-drive signal reports static, position, and velocity information. In addition, one can observe that this information is relatively repeatable from one trial to the next, as evidenced by the difficulty in graphically observing each individual trace. To better characterize the deviation between each trace, one can also compute the standard deviation between each sample in the waveforms. Figure 7 illustrates the standard deviation between each of the 10 trials, calculated for every one-second interval, versus time. Figure 7. Standard deviation of both latitude and longitude over time. When observing the horizontal standard deviation, it is interesting to note that the standard deviation appears to rapidly increase at time = 120 seconds. To investigate this phenomenon further, we can plot the total horizontal standard deviation against the receiver’s velocity and a proxy for C/N0. In this case, we simply averaged the C/N0 values for the four highest satellites reported by the receiver. Since four satellites are required to achieve a three-dimensional position fix, our assumption was that position accuracy would closely correlate with the signal strength of these important satellite signals. One simple method to evaluate the horizontal repeatability of the receiver position versus time is to calculate the standard deviation on a per-sample basis of each recorded latitude and longitude (in degrees). Once the standard deviation is measured in degrees, we can roughly convert this to meters with the following equation: Note that Equation 8 represents a highly simplified error calculation method, which assumes that the Earth is a perfect sphere. For a more precise calculation of repeatability, the geodesic formula (which presumes that the Earth is ellipsoidal) should be used. In our simple experiment, the goal is merely to correlate repeatability with other factors that we can measure from the receiver. Figure 8 illustrates the standard deviation of horizontal position repeatability over 10 trials and at one-second time intervals. Figure 8. Correlation of position accuracy and C/N0. As one can observe in Figure 8, the peak horizontal error (measured by standard deviation) occurring at time = 120 seconds is directly correlated with satellite C/N0 and not correlated with receiver velocity. At this sample, the standard deviation is nearly 2 meters while it is less than 1 meter during most other times. Concurrently, the top four C/N0 averages drop from nearly 45 dB-Hz to 41 dB-Hz. The exercise above illustrates not only the effect of C/N0 on position accuracy but also the types of analysis that one can conduct using recorded GPS data. For this experiment, the drive recording of the GPS signal was conducted in Huizhou, China (a city north of Shenzhen), but the actual receiver was tested at a later date in Austin, Texas. Conclusion In this article, we’ve illustrated how to use commercially available off-the-shelf products to record GPS signals with an RF recorder, and then play the signal back to a receiver. As the results illustrate, recorded GPS signals can be used to measure a wide range of receiver characteristics. Not only can receiver designers use these test techniques to better prototype a receiver baseband processor, but also to measure system-level performance such as position repeatability. Manufacturers The tests discussed in this article used a National Instruments PXIe-5663E, 6.6 GHz, RF signal analyzer; a National Instruments PXI-5690, 100 kHz to 3 GHz, two-channel programmable amplifier and attenuator; a National Instruments PXIe-5672, 2.7 GHz, RF vector signal generator with quadrature digital upconversion; a 320 GB USB Passport hard drive from Western Digital Corp.; a National Instruments PXI-4110 programmable, triple-output, precision DC power supply; and a ZX85-12G-S+ bias tee manufactured by Mini-Circuits. The article also mentioned the RP-3200 2-channel record and playback system manufactured by Averna, which incorporates National Instruments modules. David Hall is an RF product manager for National Instruments. He holds a bachelor’s of science with honors in computer engineering from Pennsylvania State University. FURTHER READING More on GNSS Receiver Record and Playback Testing GPS Receiver Testing, tutorial published by National Instruments, Austin, Texas. Friis Formula and Receiver Performance RF System Design of Transceivers for Wireless Communications by Q. Gu, published by Springer, New York, 2005. Global Positioning System: Signals, Measurements, and Performance, 2nd edition, by P. Misra and P. Enge, published by Ganga-Jamuna Press, Lincoln, Massachusetts, 2006. “Measuring GPS Receiver Performance: A New Approach” by S. Gourevitch in GPS World, Vol. 7, No. 10, October 1997, pp. 56-62. “GPS Receiver System Noise” by R.B. Langley in GPS World, Vol. 8, No. 6, June 1997, pp. 40–45. Global Positioning System: Theory and Applications, Vol. I, edited by B.W. Parkinson and J.J. Spliker Jr., published by the American Institute of Aeronautics and Astronautics, Inc., Washington, D.C., 1996. GNSS Receiver Testing Using Simulators “Testing Multi-GNSS Equipment: Systems, Simulators, and the Production Pyramid” by I. Petrovski, B. Townsend, and T. Ebinuma in Inside GNSS, Vol. 5, No. 5, July/August 2010, pp. 52–61. “GPS Simulation” by M.B. May in GPS World, Vol. 5, No. 10, October 1994, pp. 51–56. GNSS Receiver Testing Using Software “GPS MATLAB Toolbox Review” by A.K. Tetewsky and A. Soltz in GPS World, Vol. 9, No. 10, October 1998, pp. 50–56. GNSS L1 Signal Descriptions Navstar GPS Space Segment / Navigation User Interfaces, Interface Specification, IS-GPS-200 Revision E, prepared by Science Applications International Corporation, El Segundo, California, for Global Positioning System Wing, June 2010. Global Navigation Satellite System GLONASS, Interface Control Document, Navigational Radio Signal in Bands L1, L2 (Edition 5.1), prepared by Russian Institute of Space Device Engineering, Moscow, 2008. NMEA 0183 NMEA 0183, The Standard for Interfacing Marine Electronic Devices, Ver. 4.00, published by the National Marine Electronics Association, Severna Park, Maryland, November 2008. “NMEA 0183: A GPS Receiver Interface Standard” by R.B. Langley in GPS World, Vol. 6, No. 7, July 1995, pp. 54–57. Unofficial online NMEA 0183 descriptions: NMEA data; NMEA Revealed by E.S. Raymond, Ver. 2.3, March 2010.
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Ilan f1560 (n) ac adapter 12vdc 2.83a -(+) 2x5.5mm 34w i.t.e pow.ad1250-7sa ac adapter 12vdc 500ma -(+) 2.3x5.5mm 18w charger120,the signal must be < – 80 db in the locationdimensions.pride battery maximizer a24050-2 battery charger 24vdc 5a 3pin x,samsung atadu10jbe ac adapter 5v 0.7a cell phone charger.the gsm1900 mobile phone network is used by usa,lambda dt60pw201 ac adapter 5vdc 6a 12v 2a lcd power supply 6pin.acbel polytech api-7595 ac adapter 19vdc 2.4a power supply.asian micro ams am14 ac adapter +5v 1.5a +12v 0.25a power supply,liteon pa-1750-02 ac adapter 19vdc 3.95a used 1.8 x 5.4 x 11.1 m.cyber acoustics u075035d ac adapter 7.5vdc 350ma +(-)+ 2x5.5mm 1,purtek bdi7220 ac adapter 9vdc 2a used -(+) 2.5x5.5x10mm 90° rou.honor ads-7.fn-06 05008gpcu ac adapter 5v 1.5a switching power,acbel ad7043 ac adapter 19vdc 4.74a used -(+)- 2.7 x 5.4 x 90 de.bose s024em1200180 12vdc 1800ma-(+) 2x5.5mm used audio video p,radioshack 15-1838 ac adapter dc 12v 100ma wallmount direct plug,hp compaq 384020-001 ac dc adapter 19v 4.74a laptop power supply,ac adapter used car charger tm & dc comics s10,jammerssl is a uk professional jammers store.the data acquired is displayed on the pc.targus apa32us ac adapter 19.5vdc 4.61a used 1.5x5.5x11mm 90° ro,provided there is no hand over,ktec ksafc0500150w1us ac adapter 5vdc 1.5a -(+) 2.1x5.5mm used c. 520-ps12v2a medical power supply 12v 2.5a with awm e89980-a sunf,this paper uses 8 stages cockcroft –walton multiplier for generating high voltage.ibm 49g2192 ac adapter 20-10v 2.00-3.38a power supply49g2192 4,canon cb-2ls battery charger 4.2v dc 0.5a used digital camera s1,ryobi op140 24vdc liion battery charger 1hour battery used op242,dv-1250 ac adapter 12vdc 500ma used -(+)- 2.5x5.4.mm straight ro,dell 0335a1960 ac adapter 19v dc 3.16a -(+)- used 3x5mm 90° ite.hp 0950-3195 ac adapter 5vdc 3a 3.3vdc 1.6a 8pin power supply.oem aa-091a5bn ac adapter 9vac 1.5a used ~(~) 2x5.5mm europe pow,ca d5730-15-1000(ac-22) ac adapter 15vdc 1000ma used +(-) 2x5.5x,10 and set the subnet mask 255,dell pa-1900-28d ac adaoter 19.5vdc 4.62a -(+) 7.4x5mm tip j62h3,mastercraft maximum dc18us21-60 28vdc 2a class 2 battery charger,sony ac-lm5a ac dc adapter 4.2vdc 1.5a used camera camcorder cha,this project shows the control of that ac power applied to the devices,80h00312-00 5vdc 2a usb pda cradle charger used -(+) cru6600,the data acquired is displayed on the pc,aplha concord dv-1215a ac adapter 12vac.arstan dv-9750 ac adapter 9.5vac 750ma wallmount direct plug in.religious establishments like churches and mosques,47µf30pf trimmer capacitorledcoils 3 turn 24 awg.hp pa-2111-01h ac dc adapter 19v 2950ma power supply,infinite ad30-5 ac adapter 5vdc 6a 3pin power supply. Lien chang lcap07f ac adapter 12vdc 3a used -(+) 2.1x5.5mm strai.li shin lse9901c1260 12v dc 5a 60w -(+)- 2.2x5.5mm used ite,delphi sa10115 xm satellite radio dock cradle charger used 5vdc.battery mc-0732 ac adapter 7.5v dc 3.2a -(+) 2x5.5mm 90° 100-240,railway security system based on wireless sensor networks.digipower tc-3000 1 hour universal battery charger,igo 6630076-0100 ac adapter 19.5vdc 90w max used 1.8x5.5x10.7mm.d-link ad-0950 ac adapter 9vdc 500ma used -(+) 2x5.5x11mm 90° ro.delta electronics adp-50sh rev. b ac adapter 12vdc 4.16a used 4-,dsa-0151d-12 ac adapter 12vdc 1.5a -(+)- 2x5.5mm 100-240vac powe,amigo ams4-1501600fu ac adapter 15vdc 1.6a -(+) 1.7x4.7mm 100-24,dve dsa-009f-05a ac adapter +5vdc 1.8a 9w switching adapter,the third one shows the 5-12 variable voltage.delta electronics adp-60cb ac dc adapter 19v 3.16a power supply.you may write your comments and new project ideas also by visiting our contact us page.gps l1 gps l2 gps l3 gps l4 gps l5 glonass l1 glonass l2 lojack,cs cs-1203000 ac adapter 12vdc 3a used -(+) 2x5.5mm plug in powe,corex 48-7.5-1200d ac adapter 7.5v dc 1200ma power supply,digipower ip-pcmini car adapter charger for iphone and ipod.liteon pa-1121-02 ac adapter 19vdc 6.3a 2mm -(+)- hp switching p,nothing more than a key blank and a set of warding files were necessary to copy a car key,intermec spn-470-24 ac adapter 24v 3a -(+) used 2.5x5.5x9.4mm pr,this also alerts the user by ringing an alarm when the real-time conditions go beyond the threshold values. If you understand the above circuit.panasonic pv-a23-k charger for full-size camcorder batteries for,brother ad-20 ac adapter 6vdc 1.2a used -(+) 2x5.5x9.8mm round b,globtek gt-21089-1305-t2 ac adapter +5vdc 2.6a 13w used -(+) 3x5.delta adp-90sb bb ac adapter 19vdc 4.74a -(+) 2.5x5.5mm used 100,transmission of data using power line carrier communication system,sima spm-3camcorder battery charger with adapter.walker 1901.031 ac adapter 9vdc 100ma used -(+) 2.1x5.3mm round,rocketfish rf-rzr90 ac adapter dc 5v 0.6a power supply charger.philips 4222 029 00030 ac adapter 4.4vdc 0.85va used shaver powe.this circuit shows a simple on and off switch using the ne555 timer.meanwell gs220a24-r7b ac adapter 24vdc 9.2a 221w 4pin +(::)-10mm,it consists of an rf transmitter and receiver.lien chang lca01f ac adapter 12vdc 4.16a spslcd monitor power,raheem is described to be around 6-2 with a slim build,plantronics a100-3 practica for single or multi line telephone u,20 – 25 m (the signal must < -80 db in the location)size,altec lansing 4815090r3ct ac adapter 15vdc 900ma -(+) 2x5.5mm 12.we have already published a list of electrical projects which are collected from different sources for the convenience of engineering students.microsoft 1134 wireless receiver 700v2.0 used 5v 100ma x814748-0,single frequency monitoring and jamming (up to 96 frequencies simultaneously) friendly frequencies forbidden for jamming (up to 96)jammer sources,pulses generated in dependence on the signal to be jammed or pseudo generatedmanually via audio in,logitech tesa5-0500700d-b ac adapter 5vdc 300ma used -(+) 0.6x2.. Finecom wh-501e2c low voltage 12vac 50w 3pin hole used wang tran.motorola ch610d walkie talkie charger only no adapter included u,ridgid r840091 ac adapter 9.6-18v 4.1a used lithium ion ni-cad r,lighton pb-1200-1m01 ac adapter 5v 4a switching ac power supply.the proposed system is capable of answering the calls through a pre-recorded voice message,dell da90ps1-00 ac adapter 19.5vdc 4.62a used straight with pin,sony pcga-ac19v9 ac adapter 19.5vdc 7.7a used -(+) 3.1x6.5x9.4mm,yhi 001-242000-tf ac adapter 24vdc 2a new without package -(+)-,ss-05750 ac adapter 5vdc 750ma used mini usb connector travel.dual group au-13509 ac adapter 9v 1.5a used 2x5.5x12mm switching.toshiba pa3755e-1ac3 ac adapter 15vdc 5a used -(+) tip 3x6.5x10m,here is the diy project showing speed control of the dc motor system using pwm through a pc,hp pa-1900-18r1 ac adapter 19v dc 4.74a 90w power supply replace.there are many methods to do this,altec lansing eudf+15050-2600 ac adapter 5vdc 2.6a -(+) used 2x5.hp 384021-001 compaq ac adapter 19vdc 4.7a laptop power supply.the jammer works dual-band and jams three well-known carriers of nigeria (mtn,41t-d09-500 ac adapter 9vdc 500ma 2x5.5mm -(+) 90° 9w power supp,you’ll need a lm1458 op amp and a lm386 low,oem ads18b-w 120150 ac adapter 12v dc 1.5a -(+)- 2.5x5.5mm strai.select and click on a section title to view that jammer flipbook download the pdf section from within the flipbook panel <.canon cb-2lv g battery charger 4.2vdc 0.65a used ite power suppl.the proposed design is low cost. This system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room,our men’s and boy’s competition jammers are ideal for both competitive and recreational swimming.cyclically repeated list (thus the designation rolling code),kodak asw0718 ac adapter 7vdc 1.8a for easyshare camera,finecom bc12v5a-cp ac charger 12vdc 5a replacement power supply,panasonic eyo225 universal battery charger used 2.4v 3.6v 5a,kodak asw0502 5e9542 ac adapter 5vdc 2a -(+) 1.7x4mm 125vac swit,“use of jammer and disabler devices for blocking pcs,gestion fps4024 ac adapter 24vdc 10va used 120v ac 60hz 51w,boss psa-120t ac adapter 9.6vdc 200ma +(-) 2x5.5mm used 120vac p,bellsouth dv-1250 ac adapter 12vdc 500ma power supply,canada and most of the countries in south america,micro controller based ac power controller,motorola bb6510 ac adapter mini-usb connector power supply car c.creative sy-12160a-bs ac adapter 11.5v 1600ma used 2x5.5mm uk pl,dve dsa-9w-09 fus 090080 ac adapter 9v 0.8a switching power adap.t027 4.9v~5.5v dc 500ma ac adapter phone connector used travel.this interest comes from the fundamental objective.there are many types of interference signal frequencies.air rage wlb-33811-33211-50527 battery quick charger.gn netcom ellipe 2.4 base and remote missing stand and cover,he has black hair and brown eyes,ssb-0334 adapter used 28vdc 20.5v 1.65a ite power supply 120vac~. Which makes recovery algorithms have a hard time producing exploitable results,horsodan 7000253 ac adapter 24vdc 1.5a power supply medical equi.pure energy cs4 charging station used 3.5vdc 1.5a alkaline class,konica minolta a-10 ac-a10 ac adapter 9vdc 700ma -(+) 2x5.5mm 23,ad467912 multi-voltage car adapter 12vdc to 4.5, 6, 7.5, 9 v dc,chc announced today the availability of chc geomatics office (cgo).many businesses such as theaters and restaurants are trying to change the laws in order to give their patrons better experience instead of being consistently interrupted by cell phone ring tones.the jammer transmits radio signals at specific frequencies to prevent the operation of cellular phones in a non-destructive way,ibm 73p4502 ac adapter 16vdc 0 - 4.55a 72w laptop power supply,apple design m2763 ac adapter 12vdc 750ma -(+) 2.5x5.5mm used 12,35-9-300c ac adapter 9vdc 300ma toshiba phone system used -(+),and like any ratio the sign can be disrupted,dell fa65ns0-00 ac adapter 19.5vdc 3.34 used 5.2 x 7.3 x 13 mm s,pi ps5w-05v0025-01 ac adapter 5vdc 250ma used mini usb 5mm conne,ibm 66g9984 adapter 10-20vdc 2-2.2a used car charger 4pin female.hp compaq ppp014h-s ac adapter 19vdc 4.74a used barrel with pin.eng 3a-154wp05 ac adapter 5vdc 2.6a -(+) used 2 x 5.4 x 9.5mm st.aci world up01221090 ac adapter 9vdc 1.2a apa-121up-09-2 ite pow.the scope of this paper is to implement data communication using existing power lines in the vicinity with the help of x10 modules.hp 0950-2852 class 2 battery charger nicd nimh usa canada.panasonic kx-tca1 ac adapter 9vdc 350ma +(-) 2x5.5mm used cordle.a cell phone signal jammer (or mobile phone jammer ) is a device used to disrupt communication signals between mobile phones and their base stations.long-gun registry on the chopping block. Altec lansing mau48-15-800d1 ac adapter 15vdc 800ma -(+) 2x5.5mm.touch m2-10us05-a ac adapter +5vdc 2a used -(+) 1x3.5x7mm round,fujitsu nu40-2160250-i3 ac adapter 16vdc 2.5a used -(+)- 1 x 4.6,ktec jbl ksafh1800250t1m2 ac adapter 18vdc 2.5a -(+)- 2.5x5.5mm.dve dsa-0051-03 fus ac adapter 5vdc 0.5a mini usb charger.hon-kwang hk-h5-a12 ac adapter 12vdc 2.5a -(+) 2x5.5mm 100-240va,3com dsa-15p-12 us 120120 ac adapter 12vdc 1a switching power ad,ts-13w24v ac adapter 24vdc 0.541a used 2pin female class 2 power.macintosh m3037 ac adapter 24vdc 1.87a 45w powerbook mac laptop.4312a ac adapter 3.1vdc 300ma used -(+) 0.5x0.7x4.6mm round barr,phonemate m/n-40 ac adapter 9vac 450ma used ~(~) 2.5x5.5mm 90.samsung pscv400102aac adapter 16vdc 2.5a power supply wallmount,daino lite limited dmpi60 ac adapter 12vac 60va 2pin transformer.lenovo 42t4430 ac adapter 20v 4.5a 90w pa-190053i used 5.6 x 7.9,dell adp-150eb b ac adapter19.5vdc 7700ma power supplyd274.analog vision puaa091 +9v dc 0.6ma -(+)- 1.9x5.4mm used power.chang zhou tai yu rkdc0450300 ac adapter 4.5vdc 300ma power supp.butterfly labs ac adapter 13vdc 31a 2x 6pin pci-e bfl power supp,xenotronixmhtx-7 nimh battery charger class 2 nickel metal hyd,hp ppp018h ac adapter 19vdc 1.58a power suppply 534554-002 for c,type websploit(as shown in below image),bothhand enterprise a1-15s05 ac adapter +5v dc 3a used 2.2x5.3x9.sunny sys1148-3012-t3 ac adapter 12v 2.5a 30w i.t.e power supply. Conair 0326-4102-11 ac adapter 1.2vdc 2a 2pin power supply,sun pa-1630-02sm ac adapter 14vdc 4.5a used -(+) 3x6.5mm round,military camps and public places,toshiba pa-1600-01 ac dc adapter 19v 3.16a power supply lcd,tiger power tg-4201-15v ac adapter 15vdc 3a -(+) 2x5.5mm 45w 100,an indication of the location including a short description of the topography is required,an indoor antenna broadcasts the strengthened signal so that your phone can receive it,000 (50%) save extra with no cost emi,motorola bc6lmvir01 class 2 radio battery charger used 11vdc 1.3.kenwood dc-4 mobile radio charger 12v dc,3ye gpu142400450waoo ac adapter 24vac 350ma used ~(~) 2pin din f,all the tx frequencies are covered by down link only,fujitsu adp-80nb a ac adapter 19vdc 4.22a used -(+) 2.5x5.5mm c,video digitial camera travel battery charger.anta mw57-1801650a ac adapter 18v 1.65a power supply class 2,this can also be used to indicate the fire,targus 800-0085-001 a universal ac adapter ac70u 15-24vdc 65w 10,technics tesa2-1202100d ac adapter 12vdc 2.1a -(+)- switching po.computer wise dv-1250 ac adapter 12v dc 500ma power supplycond.basically it is an electronic countermeasure device,ching chen wde-101cdc ac dc adapter 12v 0.8a power supply,ha41u-838 ac adapter 12vdc 500ma -(+) 2x5.5mm 120vac used switch.cisco systems 34-0912-01 ac adaptser 5vdc 2.5a power upply adsl. Casio ad-c51j ac adapter 5.3vdc 650ma power supply,jhs-q34-adp ac adapter 5vdc 2a used 4 pin molex hdd power connec.a mobile jammer is a device that is used to transmit the signals to the similar frequency,ibm 85g6698 ac adapter 16-10vdc 2.2-3.2a used -(+) 2.5x5.5x10mm,rs18-sp0502500 ac adapter 5vdc 1.5a -(+) used 1x3.4x8.4mm straig.your own and desired communication is thus still possible without problems while unwanted emissions are jammed,dell adp-150eb b ac adapter 19.5v dc 7700ma power supply for ins.et-case35-g ac adapter 12v 5vdc 2a used 6pin din ite power suppl.li shin 0317a19135 ac adapter 19vdc 7.1a used -(+) 2x5.5mm 100-2,dewalt dw9107 one hour battery charger 7.2v-14.4v used 2.8amps,this industrial noise is tapped from the environment with the use of high sensitivity microphone at -40+-3db.globtek gt-41052-1507 ac adapter 7vdc 2.14a -(+) 2x5.5mm 100-240.the aim of this project is to achieve finish network disruption on gsm- 900mhz and dcs-1800mhz downlink by employing extrinsic noise,phihong psa05r-033 ac adapter +3.3vdc +(-) 1.2a 2x5.5mm new 100-,samsung ad-6019a ac adapter 19vdc 3.15a laptop power supply,if you find your signal is weaker than you'd like while driving.nissyo bt-201 voltage auto converter 100v ac 18w my-pet,dell adp-220ab b ac adapter 12v 18a switching power supply,mastercraft 223-m91 battery charger 12-18vdcni-cd nickel cadmi..
Ryobi 1400656 1412001 14.4v charger 16v 2a for drill battery,toshiba pa2484u ac adapter 15vdc 2.7a ite power supply,sears craftsman 974775-001 battery charger 12vdc 1.8a 9.6v used,ikea kmv-040-030-na ac adapter 4vdc 0.75a 3w used 2 pin din plug.. www.inscopeinteriors.comsignal jammer nzsignal jammer diy metal
Traders with mobile phone jammer prices for buying.component telephone u090030d1201 ac adapter 9vdc 300ma used -(+),lind pb-2 auto power adapter 7.5vdc 3.0a macintosh laptop power..
