The design and verification of a new class of portable wideband record-and-playback system considers the relative merits and limitations of both simulator and record/replay approaches. The authors also discuss the benefits of the different test approaches to the development and characterization of various GNSS receiver types. By Steve Hickling and Tony Haddrell As new GNSS systems become available, and users take receivers to ever more challenging environments, the need for repetitive and repeatable testing during development grows ever stronger. Simulators have traditionally demonstrated performance and repeatability in the laboratory environment, and this approach remains the only option for planned signals not yet broadcast from space. However, this approach is becoming more complex as the number of GNSS signals and their reception environments increase. Another way of testing receivers is through field trials. This allows investigation of conditions difficult to simulate, such as multiple reflections and interferers. These environments, however, are time-varying, and thus not repeatable in the true sense. Therefore, proper comparisons can only be made by assessing all competing receivers in the same trial, and any performance anomalies seen cannot necessarily be tracked down by returning to the same location at some point in the future. Furthermore, developers would like to see for themselves any such anomalies and try to understand and correct them, but it is not always desirable or practical (and certainly not economical) to put development engineers in locations scattered all over the globe. To tackle this problem, GNSS signal record-and-replay capability is gaining acceptance as a practical tool for recording a signal environment at a single point in time and replaying at will. In real terms this means a device must receive the radio signals from the GNSS satellites, reduce them to a form suitable for storage, and then recreate signals from the stored data in a manner that makes them look completely real to any receiver under test or development. Some receiver manufacturers developed their own capability to do this. Early devices were of necessity restricted in the signals they could handle and store, limited both by budget and available technologies. The basic problems are the amount of data to be stored in real time and the ability to recover it in real time. Even the GPS L1-only low bandwidth C/A code requires at least 2 Mbytes per single second of recording, or more than 100 Mbytes per minute. Fortunately, with digital storage technology advances, we can now make use of higher storage capacities (1 TByte of storage is readily available at reasonable cost) and also higher write/read bandwidths (100 MBytes per second is realistic). All we need is some hardware and a processor that can handle the data rates. Once we have our wanted signals reduced to some form of digital representation, we can simply store and retrieve them at will, handling the recordings as simple, if somewhat large, data files. This allows file distribution between equipments, and a split between making the recording in the field and replaying it in the laboratory. In fact, many manufacturers have dedicated field recording teams who send the files back to the engineers interested in the signal environments. Replaying the signals is in some ways similar to generating simulated signals. In both cases, the starting point is digital data, on the one hand recorded in the field, on the other hand calculated by mathematical algorithms using the scenario specified in the simulator. In both cases the signal is created by generating radio frequency (RF) carriers and modulating them according to the GNSS signal formats. Contrast of Two Approaches. None of the characteristics of the record/replay device replace the functionality of the simulator; in fact, both are valid tools for development and testing. For instance, it is not possible with a record/replay device to manipulate individual satellite signals, nor to introduce specific errors in the radio signals. Equally, it is not really possible with a simulator to recreate a particular physical environment made up of many reflected signals, jammers, manmade noise, and moving scenery. With a simulator, the user has control over the power of the received satellite signal, whereas in the recorder the entire signal-to-noise ratio observed at the point of reception has been recorded, and the user can only control the amplitude of the entire noise plus signal. Permanent Signal Monitoring One other aspect of raw signal recording lies outside the receiver testing topic, but is of interest for GNSS signal monitoring. It uses the ability to record GNSS signals all of the time, in this case from a good signal environment, and then to retain any time spans where an anomaly in the signals has been detected by a monitor receiver. This is comparable to recording security CCTV pictures, where we expect nearly all of the resulting files to be redundant, but can retain the interesting bits to replay over and over for further analysis. For example, if it is known that a given timing receiver installation suffers periodic loss of lock, it is possible to make a recording using the loss of lock to signpost the interesting region in much the same way as a reverse trigger on an oscilloscope. Limitations and Compromises The sheer function of recording GNSS signals off-air has some built-in limitations. First, the signal recorded represents only a snapshot of the environment, although numerous recordings can be made at, say, busy and quiet times, day and night, etc. This is really a reversal of the “non repeatability” aspect of measuring performance in a particular location. In the recording sense, we only get repeatability, with no guarantee that the scenario captured represents worst case conditions. Thus, going back to the location in the future may or may not provide similar results. In addition to this, there are some signal processing aspects that limit the fidelity of the replayed signals. The first is that any recorder must have an external GNSS antenna and a GNSS receiver front-end built in, and this combination will receive both the satellite signals and thermal noise. The level of the noise is much higher than that of the signals if we don’t do any correlation related processing, and the receiver will contribute some more noise of its own (the noise figure of the system). The second aspect is that in downconverting the radio signals to a usable frequency for sampling and storage, the recorder must use some frequency reference of its own, which will contribute some frequency uncertainty and some phase noise (or jitter on the frequency). The final aspect is the digitization of the downconverted signal to get it into a suitable form for manipulation and storage. Since we are essentially sampling noise here (with the GNSS signal buried in it) we need to look at fidelity in reproduction of the noise during playback, and the effect of any signal (a jammer or interferer) that is above the amplitude of the noise. In analyzing this last aspect, we may include the effect of any automatic gain control (AGC) used to present the correct amplitude signal to the analog to digital (A2D) converter. A New Simulation Requirement We wanted to create a much more comprehensive and flexible device than hitherto available, going part way towards the much more general (and expensive) instrumentation recorders that are currently the only alternative. The requirement is for a flexible, self-contained device that can be easily carried or transported for recording purposes, so having an internal battery and built-in control functionality, and simultaneously a device that fits neatly into a networked and externally controlled laboratory environment. The first approach was to cover all of the possible GNSS frequency bands, although as more are added with time, we realized that this needed to be moderated somewhat. So the product covers L1, L2, L5 and their derivatives for the differing GNSS systems GPS, GLONASS, Galileo, and BeiDou, and also the Inmarsat commercial band to cover the proprietary augmentation signals used by many high-accuracy receivers (see Figure 1, red outlines). FIGURE 1. Frequency bands, outlined in red, supported by the new record-and-replay device. The next decision was what bandwidths to allow at each frequency, and how much of this bandwidth could be covered at once. The limitations here are driven by the data storage requirements of the signals being recorded, and the speed that they can be written to disk. The resulting solution allows bandwidths (BW) of up to 30 MHz at each frequency, and any three such bandwidths to be recorded at once. Physically, this is implemented with three channels with the ability to record any of the available frequencies or bandwidths. The user has, therefore, flexibility to set up recording for his particular needs, which may be just L1 covering BeiDou, GPS, Galileo, and GLONASS, or an L1,L2,L5, combination for a survey type application. Of course, there are always requests for more capability, and we envisaged early on the ability to stack two devices to give six channels of 30-MHz BW for recording, say, GPS/Galileo and GLONASS at L1, GPS and GLONASS at L2, Galileo/GPS at L5, and an Inmarsat data carrier. See later for how this is achieved. The whole product has to fit in a portable box with enough battery power for more than one-hour field campaigns, and also be capable of running from mains or vehicle power. The associated antenna needs to cover all of the frequency bands. Figure 2 shows the end result in its standalone configuration. Figure 2. Portable solution for recording. One additional requirement was placed upon the design, and that is the ability to record and replay non-GNSS data simultaneously with the GNSS signals, and reproduce them, if desired, in synchronism with the replayed signals. This allows time ticks, events, assistance data, sensor data, or even video to be stored and replayed along with the raw signals. Architecture and Implementation The new record-and-replay device uses a fast computer running the Linux operating system as its control center and storage/retrieval engine. Dedicated hardware is used to format or recover the raw data, and this has access directly to the computer bus to minimize the delays in writing or reading the mass storage, which in this case is a solid state hard drive (SSD). The overall architecture is shown in Figure 3. Figure 3. Concept-level architecture. The signal recording capability hinges around the RF planning, which has the task of supplying the necessary flexibility without adding more than minimal signal degradation. For the RF functionality, the device contains a broadband front end and a three-channel RF amplifier (L1, Imarsat, and L2/L5), filtering the signal down to reasonable bandwidths for later downconversion. Three independent channels of downconversion to baseband I and Q analog signals have access to any of the RF channels and are based upon satellite TV technology architectures. The downconverters have baseband filters that can be commanded to a desired bandwidth by the control processor. This allows the use of narrower bandwidths where possible, allowing more recording time for a lower sampling rate. The baseband signals are sampled at 10 MHz or 30 MHz, paying attention to the Nyquist requirements for pre-digitisation filtering. Two bits for each of the I and Q signals are utilized for packing into the recorded file format. Figure 4 shows the arrangement. Figure 4 . The RF architecture. At this stage any additional synchronous data to be recorded, such as truth or assitance data, is inserted into the bit stream, and the data from all the channels in use is combined in a pre-determined format. Dedicated hardware is used for this, and large data buffers are provided to alleviate bottlenecks in sending data to the disks. Each file has an associated definition in a header, and contains synchronization data to allow the device to set up the replay path and recover the data bits in order to reproduce whatever combination was recorded. Note that resulting data files are given the same extension, regardless of content. Data files can be very big (at maximum bandwidth we record about 2.7 Gbytes per minute) and may be difficult to handle once recorded. To assist with this, the device has a second, removable SSD on board, allowing recorded files to be simply popped out of the caddy and shared with another device, or even mailed or couriered. The RF path for the replay consists again of three independent channels, able to generate any of the supported frequencies and modulate upon them the original signals recovered from the stored file. Once again, dedicated hardware and large buffers are needed to unpack the files and send the RF data to the correct channels or to the synchronous data outputs in the case of recorded digital data, as determined by the file header. The data representing the recorded RF is converted back to analog form and filtered before being applied to modulators which regenerate the original channelized signals. Each channel has a programmable attenuator to “level” the amplitude, and the three channels are then combined together before passing through a common attenuator to provide user control over the replayed carrier to noise ratio (C/N0). Figure 5 shows the upconverter arrangement. Figure 5. An upconverter channel. All frequencies created within the device need to be traceable to a common reference. In addition, this reference needs to be at least as good as the reference in any receiver to be tested, since both its offset from true frequency and its rates of change will be superimposed on the replayed data. Many commercial-grade GNSS receivers (such as those used in mobile phone) are specifically designed to cope with poor oscillators, for instance a low-grade temperature controlled crystal oscillator (TCXO), whereas more professional receivers may expect a couple of orders of magnitude better performance. We decided, therefore, to include an ovenized oscillator (OCXO) for use both in record and playback modes. One challenge presented by this decision is that the oven is necessarily thirsty for power, and therefore a bigger battery is needed than would otherwise be the case. The OCXO used is a 10.23-MHz component, thus allowing direct generation of the wanted GNSS frequencies using integer ratios and avoiding as much phase noise as possible in the various RF channels. A dedicated phase locked loop (PLL) generates a reference for output to other devices, and a 10-MHz input connector is provided to lock the OCXO to an external reference. These capabilities are utilized when combining two such devices, since we must have the same frequency reference in each. Apart from locking the two oscillators together, this configuration also needs time synchronization between the sampling in both devices, and this is achieved via an additional cable connected between the accessory connectors. Once time and frequency synchronized, the devices behave as a single six-channel unit, using external RF splitter/combiners for the RF connections. Design Challenges RF Total Bandwidth. The GNSS bands covered by the device range from the L5 band to the GLONASS L1 band, a total range of 480 MHz allowing for signal bandwidths. Table 1 shows the relevant bands. Whilst the RF front end must be wide open to this range, assuming the use of a single RF input port, it is obviously necessary to provide bandwidth narrowing by filtering as soon as possible, to exclude jammers or carriers using the space between the GNSS bands, and to avoid the sheer noise power overwhelming the RF circuits. Examination of the supported GNSS services shows them essentially packed into two clusters of frequencies, which provide a convenient way of filtering down the RF input into two RF “channels.” This gets the total bandwidth down to about 180 MHz. Figure 1, the opening graphic for this article, shows the groupings. Beidou B3 and Galileo E6 are currently out of scope for this product, but will be supported in a later version. The Inmarsat-supported signals are assigned their own RF path, since their structure is data modulated carriers, usually with low SNR. Elsewhere in the Inmarsat band there are more powerful carriers supporting comms traffic, which can “grab” the AGC and therefore cause loss of SNR during the digitization process. Hence this band is processed though its own RF path, maintaining as low a bandwidth as possible consistent with the frequency allocations of the various (proprietary) GNSS augmentation data carriers. Tradeoffs. Throughput of the recording or replay paths is the performance limitation of the current architecture. Thus a lot of discussions and simulations concerning possible bandwidth, sampling rates, and bit depth tradeoffs was undertaken at the outset of the design. In addition, we needed to decide whether to sample signals at an IF frequency or at baseband. Trials were conducted to determine the real rates of disk access, which are different to the often quoted write and read speeds of computer interfaces. The results of the trials and simulation led us to adopt a maximum average data rate to/from the storage system of 50 Mbytes/second, this being shown to be available over a period of many hours. Actually, at this rate we fill up a 1-Tbyte disk in about five hours. To service the GNSS signal bandwidths of interest, again there are two groups of signals. This time we are looking at either the commercial signals (“open service signals” in some systems’ parlance) used by consumer-type receivers, which are relatively narrow band, and the military, high-accuracy, or resilient signals of interest to surveying and precision applications. Therefore, we offer two sampling rates, approximately 10 and 30 MHz, to avoid building large files where more than half of the bandwidth was of no interest to the user. Next, we have to look at bit resolution. Given that we have generally a noise-like signal with Gaussian characteristics, if we were looking at digitizing at an intermediate frequency (IF), it can be shown that a 2-bit analog-to-digital converter (A2D) would be sufficient to keep the digitization losses to less than 1dB. Obviously, the fewer number of bits we need to store the better, commensurate with achieving the performance targets. Frequency planning for all of the possible frequencies and bandwidths of interest is a complex task. The requirement here was to downconvert each signal of interest to a low IF suitable for digitizing, whilst having control of the bandwidth to eliminate unwanted signals and fulfill the Nyquist criterion. In addition, we wanted each channel to be isolated from the others even when the replay path involving the generation of the IF carriers was considered. We therefore decided to downconvert to baseband for each channel, to avoid cross-contamination via the various IFs that would have to be generated for replay. In other words, we adopted an IF of zero Hz. This in turn means that the final bandwidth-determining filters are at baseband, and can readily be controlled by software means rather than having to switch RF paths. By downconverting into quadrature baseband channels, all stored signals are at the same (zero) IF, and crosstalk and imaging during upconversion is avoided. Thus the A2D architecture of 2 bits in the inphase (I) and 2 bits in the quadrature (Q) arms of the downconverted signal was adopted. Doing the calculation in terms of stored data, we see that we can operate three channels inside our target storage bandwidth, with a margin left for other features such as storing video at the same time. For 30M samples per second (SPS), each channel has 4 bits or 0.5 bytes Therefore, for three channels the storage bandwidth is 0.5 * 3 * 30 MSPS, or 45 Mbytes/s To keep the optimum A2D characteristics, the AGC is designed to adjust the signal amplitude at the converter to give a Gaussian response to the four states determined by the two bits in each arm. The AGC operates independently in each channel. Figure 6 shows the final architecture for the device in block diagram form. Figure 6. Final architecture. Real-Time Data Handling. Storage and retrieval of the digitized signals is carried out by dedicated hardware connected to the RF downconverter, the playback upconverter, and the main computer that “owns” the storage media. Large buffers allow the storage media to lag (record) and lead (playback) the real-time signals in time, and to take short breaks for housekeeping functions. Data is packed into a binary file according to a pre-determined sequence, which in turn is set by the number of channels and bandwidths in use. A file header is generated which contains all of the information necessary for reconstructing the data streams for replay. A synchronization sequence is added at the start of the file to allow recovery of the correct bits for each channel and each baseband quadrature arm, and to the correct timeslots for each component. Destroying the correct time reproduction is the most likely issue to cause faulty replay in any record/replay device. GNSS receivers don’t like discontinuous or slewing time! This approach also allows the insertion of external digital data into the file. Providing the data processing hardware is aware of the individual bits into which this data is placed, digital data recorded at the same time as the raw signals may be regenerated synchronously during replay. Thus any data that is applied to a receiver in a real time trial can be available for the same trial any time after the event. Two streams of synchronous data can be recorded per channel potentially making six serial data streams per chassis available. User Interfaces A final challenge presents itself in the case of user interfaces. Although the operational options of the device are quite complex, there is a requirement to be able to capture field data with just the equipment itself and any necessary antenna setup. Consequently, the product has a display and control keys implemented on the front panel, allowing the user comprehensive access to the internal functions using a menu system and scrolling displays. Alternatively, for operation in a lab environment, a network connected user interface is specified, and this requirement is supported by a webserver running on the main processor in the device. Thus, simply opening a web browser and connecting to the device’s IP address allows full functional control. In addition, connecting a mouse, keyboard, and monitor to the device allows access to the main processor, allowing the running of scripts thus providing full control of replays and receiver functions for running continuous tests in an automated laboratory environment. Using this approach, receiver modifications can be tested over many scenarios and locations many times each, to provide statistically relevant results, without taking up operator time. Remote monitoring is possible using the webserver. Performance Testing A range of tests and trials have been carried out to verify that the product meets its specifications, and to measure the performance in a number of real life scenarios. Repeatability, Degradation, Attenuation. The first and most obvious thing to explore is the effect of the record and playback on signal-to-noise ratio. Since the RF circuits add some noise to the signal recorded, we would expect some degradation to take place here. Also, during replay, the receiver under test adds more noise, depending on its noise figure, although this should be the same as would be added when using “live” signals. Many receivers adjust for their noise figure when reporting C/N0 numbers (C/N0 is a signal to noise measurement normalized to a 1-Hz bandwidth and is the standard reported measurement for most GNSS receivers). However, by replaying back the recorded signal and noise at a higher level than would have been received in “live” conditions, we can eliminate almost all of the degradation. In live versus replayed tests for individual satellites using a JAVAD receiver, which allows us to test all of the supported bands and constellations, we found that replay is possible within ±1 dB of the original live signals. Replayed signals were about 10 dB above the original recorded level to achieve this, effectively swamping the receiver’s noise contribution. An interesting aspect of controlling the C/N0 this way is the ability to attenuate the replayed signal and, therefore, increase the contribution of the test receiver’s noise figure. Thus, although the recorded C/N0 hasn’t changed, we can attenuate the replay level and use the receiver to add noise. This process is not linear, and we obviously have to remove nearly all of the 10-dB excess to get started. The device keeps a table of attenuation vs C/N0 reduction, allowing the user to simply dial up the required C/N0 loss. Since this depends on the receiver noise figure, effects may differ slightly from receiver to receiver. Usefully the table is user definable allowing tailoring to a specific receiver. Losses from Phase Noise, Other Factors. This category of degradation is more difficult to quantify, since the effects are on tracking and therefore range and phase measurement rather than signal to noise ratio. One way of looking at this is, therefore, to establish the positioning performance during live and replayed sessions, and measure the differences. This has some complexity, though, since putting the same signals into a receiver multiple times yields differing performance each time, meaning that we have to use some statistical analysis. Of course this isn’t possible on live signals, and is one reason why repeatable replayed signals are so important in developing GNSS receivers. Another aspect is the fact that some of the effects are differential among frequency bands (filter delays, for instance) and across bands as well (group delay) and also occur in the receiver under test, which will have been calibrated to mitigate its own contribution. Figure 7 shows a comparison of static positioning for live and replayed signals using only GPS L1 and a 10-MHz sampling rate with an ST-Ericsson receiver, whilst Figure 8 is from a JAVAD receiver using all possible signals in live mode and GPS L1/L2 and GLONASS L1 in replay. In both cases the degradation is within 1 meter always, and much less than this when statistically analyzed. Figure 7. Static position GPS L1 comparison: live left, replayed right. Figure 8. GPS L1/ L2 with GLONASS L1 comparison. Another opportunity to measure the effects is to run a zero baseline phase solution, whereby the receiver is used as the “base station” when receiving live signals which are simultaneously recorded. During replay, the same receiver is used as the “rover” with RTK corrections coming from the previously captured live session. In this setup, therefore, we are really only measuring differences in the replayed and live signals, and the usual measurement limitations of the receiver. Figure 9 shows the results of one such test, with the pseudorange and carrier phase residuals plotted. This was carried out using two devices in master/slave mode recording GPS L1, L2, L5, and GLONASS L1, L2. As can be seen, the residuals are within “normal” expectations and are measured as 0.42 m RMS for the pseudorange and 1mm RMS for the carrier phase. Figure 9. Residuals from zero baseline replay. Drive Test One of the most common uses for the recorder is to capture the signals at a particular time in a chosen “difficult” environment, A number of representative trials were carried out and we were able to demonstrate consistent results and repeatability. In some cases, the replayed signals yield better performance than live ones, which of course is possible given the differing receiver responses per signal run. Also, the more times a receivers sees the same time span, the more ephemeris and iono data it can build up, especially true of built up areas where data acquisition is difficult. Figure 10 shows a small section of the City of Coventry in the UK, where the green trace is the “live” plot and the replayed one is in orange. Much of this route is under roads or buildings. Figure 10. Live and replayed drive around in Coventry. Dynamic Range and Fidelity When jamming signals are introduced, the dynamic range comes into play. The earlier discussion of the 2-bit I and 2-bit Q architecture is tested here as the performance of the AGC and A2D is critical in maintaining the fidelity of the GNSS signals in a jamming environment. Note that we are not addressing deliberate jamming here, any “controlled” jammers can be added with an RF mixer at replay. Instead, we are concerned with the everyday jamming environment encountered just about everywhere electronic equipment is deployed. A test was carried out to determine the dynamic range of record/playback paths. A simulator was used as a GPS L1 signals source, and progressively larger jamming signal added via an RF power combiner. The resultant C/N0 in a test receiver was plotted using the live signals which were recorded at the same time. A subsequent replay of those signals was then plotted on top of the original C/N0s. The result is in Figure 11. Figure 11. Results of the increasing jammer test. As can be seen, with low jammer powers the real-time and replayed C/N0s track very closely. The ST-Ericsson receiver we used has some signal processing mitigation built in, and so only shows slow degradation as the jammer power is increased. In the real-time run, it was able to track satellites with the J/S ratio greater than 44 dB (and therefore >25 dB above the noise) On the replayed line, we see the dynamic range limitations start to dominate the replayed signal when the J/S reaches about 30 dB, or 11 dB above the noise, which aligns well with the theoretical analysis of the digitization strategy. This range is sufficient for most environments encountered in real tests. In Use and Additional Capabilities With so much flexibility we find that users have a diverse range of applications for the device. These range from multi-constellation usage at L1 only, allowing BeiDou, Galileo, GLONASS, and GPS to be captured, to full six-channel recordings using GPS, GLONASS, and Galileo at L1, L2, and L5 along with an Inmarsat-based assistance channel. For the first time in this class of device, recording of the “military” bandwidth signals is possible. User feedback has been favorable, especially since the unit opens up new capabilities for receiver development and testing. A small margin of recording bandwidth has been put to use with the ability to record video alongside the raw GNSS signals, and to replay it simultaneously. This allows developers not only to see the performance of their receiver in difficult signal environments, but also to gain a visual idea of the physical environment. Figure 12 shows a receiver control panel along with video pictures of the recorded environment. Figure 12. GPS L1 and video synchronized replay Conclusion Early user feedback has validated the concept behind the device. Although the device will cover additional GNSS constellations and bands as they become operational, for the present the technology is stretched about as far as it can be consistent with the development of a timely and cost effective device. We will continue to address the compromises in the search for more performance, no doubt pushed by user demands. Acknowledgment The authors thank their colleagues at Integrated Navigation Systems and Spirent UK for support and access to design and user information. Manufacturer This article describes the GSS6425 from Spirent Communication. Steve Hickling obtained his joint physics and electronics degree from the University of Birmingham. He is responsible for Spirent’s GNSS test solutions as lead product manager in the positioning business. Tony Haddrell obtained his degree in physics at Imperial College, London, and is technical director at integrated Navigation Systems. He is a consultant to GNSS companies and a visiting lecturer at Nottingham University.
cel phone jammerTai 41a-16-250 ac adapter 16v 250ma used 2.5x5.5x13mm 90° round,linksys wa15-050 ac adapter 5vdc 2.5a used -(+) 2.5x5.5mm round.panasonic bq-390 wall mount battery charger 1.5v dc 550ma x 4 us,power supply unit was used to supply regulated and variable power to the circuitry during testing.toshiba tec 75101u-b ac dc adapter +24v 3.125a 75w power supply,2 w output powerphs 1900 – 1915 mhz,toshiba adp-60fb 19vdc 3.42a gateway laptop power supply.ibm 11j8627 ac adapter 19vdc 2.4a laptop power supply,sony ericsson cst-18 ac adapter 5vdc 350ma cellphone charger,liteon pa-1900-08hn ac adapter 19vdc 4.74a 90w used,vt600 gps tracker has specified command code for each different sms command,energizer pl-7526 ac adapter6v dc 1a new -(+) 1.5x3.7x7.5mm 90.hp c6409-60014 ac adapter 18vdc 1.1a -(+)- 2x5.5mm power supply.apple m7783 ac adapter 24vdc 1.04a macintosh powerbook duo power,motomaster eliminator bc12v5a-cp ac charger 5 12v dc 5a.archer 273-1404 voltage converter 220vac to 110vac used 1600w fo,eng 3a-161wp05 ac adapter 5vdc 2.6a -(+) 2x5.5mm used 100vac swi,ibm adp-160ab ac adapter 12vdc 13.33a 6pin molex power supply.fujitsu nu40-2160250-i3 ac adapter 16vdc 2.5a used -(+)- 1 x 4.6,replacement pa-1700-02 ac adapter 20v 4.5a power supply,add items to your shopping list,moso xkd-c2000ic5.0-12w ac adapter 5vdc 2a used -(+) 0.7x2.5x9mm,ac adapter 220v/120v used 6v 0.5a class 2 power supply 115/6vd,nikon mh-18 quick charger 8.4vdc 0.9a used battery power charger,oem ads18b-w 220082 ac adapter 22vdc 818ma used -(+)- 3x6.5mm it,the pki 6160 is the most powerful version of our range of cellular phone breakers.gsm 900/1800 for european cellular networks and.motorola psm5049a ac adapter dc 4.4v 1.5a cellphone charger,government and military convoys.a constantly changing so-called next code is transmitted from the transmitter to the receiver for verification,remember that there are three main important circuits.from the smallest compact unit in a portable,apx sp7970 ac adapter 5vdc 5a 12v 2a -12v 0.8a 5pin din 13mm mal,please see our fixed jammers page for fixed location cell.ge tl26511 0200 rechargeable battery 2.4vdc 1.5mah for sanyo pc-,replacement pa-1700-02 ac adapter 19v 3.42a used.crestron gt-21097-5024 ac adapter 24vdc 1.25a new -(+)- 2x5.5mm.with the antenna placed on top of the car.safety1st ha28uf-0902cec ac adapter 9vdc 200ma used +(-) 1x3.5x9,information including base station identity.delta adp-135db bb ac adapter 19vdc 7110ma used,hp pa-1650-02h ac adapter 18.5vdc 3.5a -(+) 1.5x5mm ppp009l roun,toshiba up01221050a 06 ac adapter 5vdc 2.0a psp16c-05ee1,netbit dsc-51f-52p us ac adapter 5.2v 1a switching power supply. Ar 35-12-100 ac adapter 12vdc 100ma 4w power supply transmiter.this paper describes the simulation model of a three-phase induction motor using matlab simulink,atlinks 5-2418 ac adapter 9vac 400ma ~(~) 2x5.5mm 120vac class 2.black & decker fsmvc spmvc nicd charger 9.6v-18vdc 0.8a used pow,black & decker ua060020 ac adapter 6v ac ~ 200ma used 2x5.5mm,this noise is mixed with tuning(ramp) signal which tunes the radio frequency transmitter to cover certain frequencies,ibm pa-1121-07ii ac adapter 16vdc 7.5a 4pin female power supply,mascot 2415 ac adapter 1.8a used 3 pin din connector nicd/nimh c,cui 3a-501dn09 ac adapter 9v dc 5a used 2 x 5.5 x 12mm.digital h7827-aa ac adapter 5.1vdc 1.5a 12.1vdc 0.88a used 7pin.and it does not matter whether it is triggered by radio,reverse polarity protection is fitted as standard,exact coverage control furthermore is enhanced through the unique feature of the jammer.effectively disabling mobile phones within the range of the jammer,htc psaio5r-050q ac adapter 5v dc 1a switching usb power supply,4.5v-9.5vdc 100ma ac adapter used cell phone connector power sup.blocking or jamming radio signals is illegal in most countries,cs cs-1203000 ac adapter 12vdc 3a used -(+) 2x5.5mm plug in powe,cyber acoustics md-75350 ac adapter 7.5vdc 350ma power supply,cidco dv-9200 ac adapter 9vdc 200ma used -(+) 2.2x5.4mm straight.jvc puj44141 vhs-c svc connecting jig moudule for camcorder.pc based pwm speed control of dc motor system.acbel ada017 ac adapter 12vdc 3.33a used -(+) 2.5x6.2x9mm round,black and decker etpca-180021u2 ac adapter 26vdc 210ma class 2,casio ad-a60024iu ac adapter 6vdc 200ma used +(-) 2x5.5x9.6mm ro,what is a cell phone signal jammer,lenovo adp-65kh b ac adapter 20vdc 3.25a -(+)- 2.5x5.5x12.5mm,motorola 527727-001-00 ac adapter 9vdc 300ma 2.7w used -(+)- 2.1.energy ea1060a fu1501 ac adapter 12-17vdc 4.2a used 4x6.5x12mm r.delta eadp-45bb b ac adapter 56vdc 0.8a used -(+) 2.5x5.5x10.4mm,konica minolta ac-4 ac adapter 4.7v dc 2a -(+) 90° 1.7x4mm 120va.replacement ac adapter 15dc 5a 3x6.5mm fo acbel api4ad20 toshiba.globtek gt-21089-1509-t3 ac adapter 9vdc 1a used -(+) 2.5x5.5mm,the company specializes in counter-ied electronic warfare,km km-240-01000-41ul ac adapter 24vac 10va used 2pin female plug.apd da-36j12 ac dc adapter 12v 3a power supply,> -55 to – 30 dbmdetection range.all these security features rendered a car key so secure that a replacement could only be obtained from the vehicle manufacturer,motorola dch3-050us-0303 ac adapter 5vdc 550ma used usb mini ite,acbel api3ad05 ac adapter 19vdc 4.74a used 1 x 3.5 x 5.5 x 9.5mm,tech std-1225 ac adapter 12vdc 2.5a used -(+) 2.3x5.5x9.8mm roun,finecom i-mag 120eu-400d-1 ac adapter 12vdc 4a -(+) 1.7x4.8mm 10,linksys mt10-1050200-a1 ac adapter 5v 2a switching power supply.l.t.e gfp121u-0913 ac adapter 9vdc 1.3a -(+) used 2x5.5mm. Solar energy measurement using pic microcontroller,meikai pdn-48-48a ac adapter 12vdc 4a used -(+) 2x5.5mm 100-240v,please pay special attention here,li shin lse9901b1260 ac adapter12vdc 5a 60w used 4pin din power,casio phone mate m/n-90 ac adapter 12vdc 200ma 6w white colour.foreen 35-d12-100 ac adapter12vdc 100ma used90 degree right,khu045030d-2 ac adapter 4.5vdc 300ma used shaver power supply 12,avaya 1151b1 power injector 48v 400ma switchin power supply,5.2vdc 450ma ac adapter used phone connector plug-in,adapter tech std-0502 ac adaptor 5vdc 2a -(+) 2x5.5mm used 100-1.chc announced today the availability of chc geomatics office (cgo),oem ad-0760dt ac adapter 7.vdc 600ma new -(+)- 2.1x5.4x10mm.dell lite on la65ns2-01 ac adapter 19.5vdc 3.34a used -(+) pin.replacement ac adapter 19v dc 4.74a desktop power supply same as,compaq pa-1071-19c ac adapter 18.5v dc 3.8a power supply,anoma aspr0515-0808r ac adapter 5vdc 0.8a 15vdc 0.75a 5pin molex.game elements gsps214 car adapter for playstaion 2condition: n,5 ghz range for wlan and bluetooth,a mobile phone jammer prevents communication with a mobile station or user equipment by transmitting an interference signal at the same frequency of communication between a mobile stations a base transceiver station,automatic telephone answering machine,car charger 12vdc 550ma used plug in transformer power supply 90,acbel polytech api-7595 ac adapter 19vdc 2.4a power supply.sino-american sa120a-0530v-c ac adapter 5v 2.4a class 2 power su,motorola psm5037b travel charger 5.9v 375ma ac power supply spn5,philips hs8000 series coolskin charging stand with adapter,digipos retail blade psu2000 power supply 24vdc 8.33a ac adapter,therefore the pki 6140 is an indispensable tool to protect government buildings.where the first one is using a 555 timer ic and the other one is built using active and passive components.radio shack 23-243 ac dc adapter 12v 0.6a switching power supply,lectroline 41a-d15-300(ptc) ac adapter 15vdc 300ma used -(+) rf,lei power converter 220v 240vac 2000w used multi nation travel a,ibm 2684292 ac adapter 15v dc 2.7a used 3x5.5x9.3mm straight.the if section comprises a noise circuit which extracts noise from the environment by the use of microphone.3g network jammer and bluetooth jammer area with unlimited distance,hi capacity ac-b20h ac adapter 15-24vdc 5a 9w used 3x6.5mm lapto.ningbo taller electrical tl-6 ac adapter 6vdc 0.3a used 2.1x5.4.laptopsinternational lse0202c1990 ac adapter 19vdc 4.74a used,jvc aa-v40u ac adapter 7.2v 1.2a(charge) 6.3v 1.8a(vtr) used,basler be 25005 001 ac adapter 10vac 12va used 5-pin 9mm mini di,hipro hp-o2040d43 ac adapter 12vdc 3.33a used -(+) 2.5x5.5mm 90.xiamen keli sw-0209 ac adapter 24vdc 2000ma used -(+)- 2.5x5.5mm.this blocker is very compact and can be easily hide in your pocket or bag.garmin fsy120100uu15-1 ac adapter 12.0v 1.0a 12w gps charger,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. This circuit analysis is simple and easy,apd wa-18g12u ac adapter 12vdc 1.5a -(+)- 2.5x5.5mm 100-240vac u,ultra energy 1018w12u2 ac adapter 12vdc 1.5a used -(+) 3x5.5mm r.transformer 12vac power supply 220vac for logic board of coxo db.flextronics kod-a-0040adu00-101 ac adapter 36vdc 1.1a 40w 4x5.6,65w-dlj004 replacement ac adapter 19.5v 3.34a laptop power suppl.lei mt15-5050200-a1 ac adapter 5v dc 2a used -(+) 1.7x4x9.4mm,linksys ls120v15ale ac adapter 12vdc 1.5a used -(+) 2x5mm 100-24,get your own music profile at last,adp-90ah b ac adapter c8023 19.5v 4.62a replacement power supply,ad-187 b ac adapter 9vdc 1a 14w for ink jet printer,li shin lse9802a1240 ac adapter 12v 3.3a 40w power supply 4 pin,delta sadp-185af b 12vdc 15.4a 180w power supply apple a1144 17",fj fj-sw1203000t ac adapter 12vdc 3000ma used -(+) shielded wire,airlink wrg10f-120a ac adapter 12vdc 0.83a -(+) 2x5.5mm 90° powe,dechang long-0910b ac dc adapter 9v dc 1a 2 x 5.5 x 10.2mm used.for any further cooperation you are kindly invited to let us know your demand,frequency counters measure the frequency of a signal.delta pcga-ac19v1 ac adapter 19.5v 4.1a laptop sony power supply,hy-512 ac adapter 12vdc 1a used -(+) 2x5.5x10mm round barrel cla.ac power control using mosfet / igbt.bay networks 950-00148 ac adapter 12v dc 1.2a 30w power supply,liteon pa-1600-2a-lf ac adapter 12vdc 5a used -(+) 2.5x5.5x9.7mm,in common jammer designs such as gsm 900 jammer by ahmad a zener diode operating in avalanche mode served as the noise generator,chicony cpa09-020a ac adapter 36vdc 1.1a 40w used -(+)- 4.2 x 6,new bright a865500432 12.8vdc lithium ion battery charger used 1,the sharper image ma040050u ac adapter 4vdc 0.5a used -(+) 1x3.4.ibm lenovo 92p1020 ac adapter 16vdc 4.5a used 2.5x5.5mm round ba.replacement vsk-0725 ac adapter 7.9vdc 1.4a power supply for pan.dongguan yl-35-030100a ac adapter 3vac 100ma 2pin female used 12,canon k30216 ac adapter 24v 0.5a battery charger,goldfar son-erik750/z520 ac car phone charger used,black & decker 143028-05 ac adapter 8.5vac 1.35amp used 3x14.3mm,dve dsc-6pfa-05 fus 050100 ac adapter +5v 1a used -(+)- 1x3.5mm.changzhou un-d7.2v200 ac dc adapter 7.2vdc 200ma -(+) used 120va,230 vusb connectiondimensions.dve dsa-0421s-12330 ac adapter 13v 3.8a switching power supply,8 kglarge detection rangeprotects private informationsupports cell phone restrictionscovers all working bandwidthsthe pki 6050 dualband phone jammer is designed for the protection of sensitive areas and rooms like offices,seiko sii pw-0006-u1 ac adapter 6vdc 1.5a +(-) 3x6.5mm 120vac cl.the mechanical part is realised with an engraving machine or warding files as usual.it has the power-line data communication circuit and uses ac power line to send operational status and to receive necessary control signals,atc-520 dc adapter used 1x3.5 travel charger 14v 600ma,you may write your comments and new project ideas also by visiting our contact us page,mbsc-dc 48v-2 ac adapter 59vdc 2.8a used -(+) power supply 100-1. Bestec bpa-301-12 ac adapter 12vdc 2.5a used 3 pin 9mm mini din,cui 48-12-1000d ac adapter 12vdc 1a -(+)- 2x5.5mm 120vac power s.aztech swm10-05090 ac adapter 9vdc 0.56a used 2.5x5.5mm -(+)- 10.hy2200n34 ac adapter 12v 5vdc 2a 4 pin 100-240vac 50/60hz,a spatial diversity setting would be preferred,kodak easyshare camera dock ii cx4200 series with 7v ac adapter.microsoft dpsn-10eb xbox 360 quick charge kit,conversion of single phase to three phase supply,lite-on pa-1650-02 ac dc adapter 20v 3.25a power supply acer1100,golden power gp-lt120v300-ip44 ac adapter 12v 0.3a 3.6w cut wire.condor 3a-181db12 12v dc 1.5a -(+)- 2x5.4mm used ite switch-mode.several noise generation methods include.delta sadp-65kb d ac adapter 19vdc 3.42a -(+) 1.7x5.5mm used rou,sony cechza1 ac adapter 5vdc 500ma used ite power supply 100-240,delta electronics adp-36db rev.a ac power adapter ast laptop,black & decker vp130 versapack battery charger used interchangea.sagemcom nbs24120200vu ac adapter 12vdc 2a used -(+) 2.5x5.5mm 9.li shin lse9802a2060 ac adapter 20vdc 3a 60w used -(+) 2.1x5.5mm.solytech ad1712c ac adapter 12vdc 1.25a 2x5.5mm used 100-240vac.this circuit shows the overload protection of the transformer which simply cuts the load through a relay if an overload condition occurs,ibm pa-1121-071 ac adapter 16vdc 7.5a used 4-pin female 02k7086.xata sa-0022-02 automatic fuses,kodak mpa7701l ac adapter 24vdc 1.8a easyshare dock printer 6000.citizen ad-420 ac adapter 9vdc 350ma used 2 x 5.5 x 9.6mm,soneil 2403srm30 ac adapter +24vdc 1.5a used cut wire battery ch,acbel api3ad14 19vdc 6.3a used -(+)- 2.5x5.5mm straight round,delta eadp-10ab a ac adapter 5v dc 2a used 2.8x5.5x11mm,ault t41-120750-a000g ac adapter 12vac 750ma used ~(~)2.5x5.5.optionally it can be supplied with a socket for an external antenna,foreen industries ltd. 28-d09-100 ac adapter 9v dc 100ma used 2,manufactures and delivers high-end electronic warfare and spectrum dominance systems for leading defense forces and homeland security &.li shin 0226b19150 ac adapter 19vdc 7.89a -(+) 2.5x5.5mm 100-240.he sad5012se ac adapter 12vdc 4.3a used -(+) 2x5.5x11.2mm round,philips consumer v80093bk01 ac adapter 15vdc 280ma used direct w,edac premium power pa2444u ac adapter 13v dc 4a -(+)- 3x6.5mm 10,which is used to test the insulation of electronic devices such as transformers.ma-1210-1 ac adapter 12vdc 1a used car cell phone charger,2 ghzparalyses all types of remote-controlled bombshigh rf transmission power 400 w.hp compaq hstnn-la09 pa-1151-03hh ac adapter19v dc 7.89a new 5.2100 to 2200 mhz on 3g bandoutput power,detector for complete security systemsnew solution for prison management and other sensitive areascomplements products out of our range to one automatic systemcompatible with every pc supported security systemthe pki 6100 cellular phone jammer is designed for prevention of acts of terrorism such as remotely trigged explosives.asus ad59230 ac adapter 9.5vdc 2.315a laptop power supply.this project utilizes zener diode noise method and also incorporates industrial noise which is sensed by electrets microphones with high sensitivity,kyocera txtvl10101 ac adapter 5vdc 0.35a used travel charger ite. Ault bvw12225 ac adapter 14.7vdc 2.25a used safco snap on connec,samsung tad437 jse ac adapter 5vdc 0.7a used.travel charger powe.at&t sil s005iu060040 ac adapter 6vdc 400ma -(+)- 1.7x4mm used.apple powerbook m1893 ac adapter 16vdc 1.5a 16v 1a used 4 pin di.apple a1202 ac adapter 12vdc 1.8a used 2.5x5.5mm straight round,konica minolta a-10 ac-a10 ac adapter 9vdc 700ma -(+) 2x5.5mm 23,people might use a jammer as a safeguard against sensitive information leaking.delta electronics adp-40sb a ac adapter 16v dc 2.5a used,dve dsa-6pfa-05 fus 070070 ac adapter +7vdc 0.7a used,this project shows the system for checking the phase of the supply.psp electronic sam-pspeaa(n) ac adapter 5vdc 2a used -(+) 1.5x4x,ab41-060a-100t ac adapter 5vdc 1a.cincon electronics tr36a15-oxf01 ac adapter 15v dc 1.3a power su,jobmate battery charger 12v used 54-2778-0 for rechargeable bat.coleco 74942 ac adapter +5vdc 0.9a -5v 0.1a +12v 0.3a used 4pin,some people are actually going to extremes to retaliate.ibm 07h0629 ac adapter 10vdc 1a used -(+)- 2 x 5 x 10 mm round b,nyko aspw01 ac adapter 12.2vdc 0.48a used -(+) 2x5.5x10mm round,altec lansing a1664 ac adapter 15vdc 800ma used -(+) 2x,this system uses a wireless sensor network based on zigbee to collect the data and transfers it to the control room.radioshack 43-3825 ac adapter 9vdc 300ma used -(+) 2x5.5x11.9mm.wireless mobile battery charger circuit.pc based pwm speed control of dc motor system.dell pa-1900-02d ac adapter 19.5vdc 4.62a 5.5x7.4mm -(+) used 10,the common factors that affect cellular reception include.lg pa-1900-08 ac adapter 19vdc 4.74a 90w used -(+) 1.5x4.7mm bul,delta adp-60bb ac dc adapter 19v 3.16a laptop power supply,intelligent jamming of wireless communication is feasible and can be realised for many scenarios using pki’s experience.desktop 6 antennas 2g 3g 4g wifi/gps jammer without car charger,darelectro da-1 ac adapter 9.6vdc 200ma used +(-) 2x5.5x10mm rou, cell phone jammer device .smart 273-1654 universal ac adapter 1.5 or 3vdc 300ma used plug-,this project creates a dead-zone by utilizing noise signals and transmitting them so to interfere with the wireless channel at a level that cannot be compensated by the cellular technology,ibm 02k6750 ac adapter 16vdc 4.5a -(+) 2.5x5.5mm 100-240vac used.this project shows the control of appliances connected to the power grid using a pc remotely,delta electronics adp-50sh rev. b ac adapter 12vdc 4.16a used 4-,shanghai dy121-120010100 ac adapter 12v dc 1a used -(+) cut wire.olympus ps-bcm2 bcm-2 li-on battery charger used 8.35vdc 400ma 1.condor dsa-0151d-12 ac adapter 12v dc 1.5a2pins mo power suppl.sony dcc-e345 ac adapter 4.5v/6v 1.5v/3v 1000ma used -(+)-.austin adp-bk ac adapter 19v dc 1.6a used 2.5x5.5x12.6mm,d-link af1805-a ac adapter 5vdc 2.5a3 pin din power supply,rocketfish kss12_120_1000u ac dc adapter 12v 1a i.t.e power supp.fixed installation and operation in cars is possible. Adjustable power phone jammer (18w) phone jammer next generation a desktop / portable / fixed device to help immobilize disturbance,a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible.hp ppp017l ac adapter 18.5vdc 6.5a 5x7.4mm 120w pa-1121-12hc 391,replacement pa-1700-02 ac adapter 19vdc 4.74a used -(+) 2.7x5.5m,toshiba pa3241u-2aca ac adapter 15vdc 3a used -(+) 3x6.5mm 100-2,this project shows the automatic load-shedding process using a microcontroller.this project shows a temperature-controlled system,thinkpad 40y7649 ac adapter 20vdc 4.55a used -(+)- 5.5x7.9mm rou,ault p48480250a01rg ethernet injector power supply 48vdc 250ma.in order to wirelessly authenticate a legitimate user,sp12 ac adapter 12vdc 300ma used 2 pin razor class 2 power suppl,dell pa-1470-1 ac adapter 18v 2.6a power supply notebook latitud,mastercraft maximum 54-3107-2 multi-charger 7.2v-19.2vdc nicd,toshiba pa3080u-1aca paaca004 ac adapter 15vdc 3a used -(+)- 3x6,power rider sf41-0600800du ac adapter 6vdc 800ma used 2 pin mole.ibm 02k6542 ac adapter 16vdc 3.36a -(+) 2.5x5.5mm 100-240vac use,briefs and team apparel with our online design studio,globtek dj-60-24 ac adapter 24vac 2.5a class 2 transformer 100va,bestec ea0061waa ac adapter +12vdc 0.5a 6w used 2 x 5 x 10mm,radio remote controls (remote detonation devices).cui 3a-501dn12 ac adapter used 12vdc 4.2a -(+)- 2.5x5.5mm switch,protection of sensitive areas and facilities.lei nu40-2120333-i3 ac adapter 12vdc 3.33v used -(+) 2.5x5.5mm 9.skynet hyp-a037 ac adapter 5vdc 2400ma used -(+) 2x5.5mm straigh,nokia acp-12u ac adapter 5.7vdc 800ma used 1x3.5mm cellphone 35,9-12v dc charger 500-1000ma travel iphone ipod ac adapter wall h,hp 384020-002 compaq ac adapter 19vdc 4.74a laptop power supply.compaq evp100 ac dc adapter 10v 1.5a 164153-001 164410-001 4.9mm,fujitsu ca01007-0520 ac adapter 16v dc 2.7a new 4.5x6x9.7mm,hipro hp-a0652r3b ac adapter 19v 3.42a used 1.5x5.5mm 90°round b,finecom bc12v5a-cp ac charger 12vdc 5a replacement power supply.. s-cell phone and gps jammers wikiraptor cell phone jammercell phone jammer Brockvilleradar detector cell phone jammercell phone jammer Drydencell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombecell phone jammer Lacombe
Leinu70-1120520 ac adapter 12vdc 5.2a ite power supply desktop,noise generator are used to test signals for measuring noise figure.black&decker ua-0602 ac adapter 6vac 200ma used 3x6.5mm 90° roun,amperor adp-90dca ac adapter 18.5vdc 4.9a 90w used 2.5x5.4mm 90.. http://www.bluzzin.net/gps-signal-blockers-c-107.html
Samsung pscv400102aac adapter 16vdc 2.5a power supply wallmount,tiger power tg-6001-12v ac adapter 12vdc 5a used 3 x 5.5 x 10.2.automatic telephone answering machine.sony ac-e351 ac adapter 3v 300ma power supply with sony bca-35e,linearity lad1512d52 ac adapter 5vdc 2a used -(+) 1.1x3.5mm roun.1800 to 1950 mhztx frequency (3g),. global-adapters.com
