By Christopher J. Hegarty
Based upon lessons learned from the LightSquared situation, the author identifies important considerations for GPS spectrum interference standards, recommended by the PNT EXCOM for future commercial proposals in bands adjacent to the RNSS band to avoid interference to GNSS.
On January 13, 2012, the U.S. National Positioning, Navigation, and Timing Executive Committee (PNT EXCOM) met in Washington, D.C., to discuss the latest round of testing of the radiofrequency compatibility between GPS and a terrestrial mobile broadband network proposed by LightSquared. The proposed network included base stations transmitting in the 1525 – 1559 MHz band and handsets transmitting in the 1626.5 – 1660.5 MHz band. These bands are adjacent to the 1559 – 1610 MHz radionavigation satellite service (RNSS) band used by GPS and other satellite navigation systems. Based upon the test results, the EXCOM unanimously concluded that “both LightSquared’s original and modified plans for its proposed mobile network would cause harmful interference to many GPS receivers,” and that further “there appear to be no practical solutions or mitigations” to allow the network to operate in the near-term without resulting in significant interference.
The LightSquared outcome was a lose-lose in the sense that billions were spent by the investors in LightSquared and, as noted by the EXCOM, “substantial federal resources have been expended and diverted from other programs in testing and analyzing LightSquared’s proposals.” To avoid a similar situation in the future, the EXCOM proposed the development of “GPS Spectrum interference standards that will help inform future proposals for non-space, commercial uses in the bands adjacent to the GPS signals and ensure that any such proposals are implemented without affecting existing and evolving uses of space-based PNT services.”
This article identifies and describes several important considerations in the development of GPS spectrum interference standards towards achieving the stated EXCOM goals. These include the identification of characteristics of adjacent band systems and an assessment of the susceptibility of all GPS receiver types towards interference in adjacent bands. Also of vital importance to protecting GPS receivers is an understanding of the user base, applications, and where the receivers for each application may be located while in use. This information, along with the selection of proper propagation models, allows one to establish transmission limits on new adjacent-band systems that will protect currently fielded GPS receivers. The article further comments on the implications of the evolution of GPS and foreign satellite navigation systems upon the development of efficacious spectrum interference standards.
Adjacent Band Characteristics
The type of adjacent-band system for which there is currently the greatest level of interest is a nationwide wireless fourth-generation (4G) terrestrial network to support the rapidly growing throughput demands of personal mobile devices. Such a nationwide network would likely consist of tens of thousands of base stations distributed throughout the United States and millions of mobile devices. The prevalent standard at the present time is Long Term Evolution (LTE), which is being deployed by all of the major U.S. carriers. LTE and Advanced LTE provide an efficient physical layer for mobile wireless services. Worldwide Interoperability for Microwave Access (WiMAX) is a competing wireless communication standard for 4G wireless that is a far-distant second in popularity.
For the purposes of the discussion within this article, an LTE network is assumed with characteristics similar to that proposed by LightSquared but perhaps with base stations and mobile devices that transmit upon different center frequencies and bandwidths. The primary characteristics include:
Tens of thousands of base stations nationwide, reusing frequencies in a cellular architecture, with the density of base stations peaking in urban areas.
Base-station antennas at heights from sub-meter to 150 meters above ground level (AGL), with a typical height of 20–30 meters AGL. Each base station site has 1–3 sector antennas mounted on a tower such that peak power is transmitted at a downtilt of 2–6 degrees below the local horizon, with a 60–70 degree horizontal 3-dB beamwidth and 8–9 degree vertical 3-dB beamwidth.
Peak effective isotropic radiated power (EIRP) in the vicinity of 20–40 dBW (100–10,000 W) per sector.
Mobile devices transmit at a peak EIRP of around 23 dBm (0.2 W), but substantially lower most of the time when lower power levels suffice to achieve a desired quality of service as determined using real-time power control techniques.
As LTE uses efficient transmission protocols, emissions can be accurately modeled as brickwall, that is, confined to a finite bandwidth around the carrier.
Throughout this article it will be presumed that LTE emissions in the bands authorized for RNSS systems such as GPS will be kept sufficiently low through regulatory means.
The opening photo shows a typical base-station tower, with three sectors per cellular service provider and with multiple service providers sharing space on the tower, including non-cellular fixed point microwave providers. As a cellular network is being built out, coverage is at first most important, and many base-station sites will use minimum downtilt and peak EIRPs within the ranges described above. As the network matures, capacity becomes more important. High-traffic cells are split through the introduction of more base stations, and this is commonly accompanied by increased downtilts and lower EIRPs.
The assumed characteristics for adjacent band systems plays a paramount role in determining compatibility with GPS, and obviously lower-power adjacent-band systems would be more compatible. If compatibility with GPS precludes 4G network implementation on certain underutilized frequencies adjacent to RNSS bands, then it may be prudent to refocus attention for these bands on alternative lower-power systems.
GPS Receiver Susceptibility
Over the past two years, millions of dollars have been expended to measure or analyze the susceptibility of GPS receivers to adjacent band interference as part of U.S. regulatory proceedings for LightSquared. Measurements were conducted through both radiated (see photo) and conducted tests at multiple facilities, as well as in a live-sky demonstration in Las Vegas. This section summarizes the findings for seven categories of GPS receivers. These categories, which were originally identified in the Federal Communications Commission (FCC)-mandated GPS-LightSquared Technical Working Group (TWG) formed in February 2011, are: aviation, cellular, general location/navigation, high-precision, timing, networks, and space-based receivers.
Aviation. Certified aviation GPS receivers are one of the few receiver types for which interference requirements exist. These requirements take the form of an interference mask (see Figure 1) that is included in both domestic and international standards. Certified aviation GPS receivers must meet all applicable performance requirements in the presence of interference levels up to those indicated in the mask as a function of center frequency. In Figure 1 and throughout this article, all interference levels are referred to the output of the GPS receiver passive-antenna element. Although the mask only spans 1500–1640 MHz, within applicable domestic and international standards the curves are defined to extend over the much wider range of frequencies from 1315 to 2000 MHz.
Figure 1. Certified aviation receiver interference mask.
A handful of aviation GPS receivers were tested against LightSquared emissions in both conducted and radiated campaigns. The results indicated that these receivers are compliant with the mask with potentially some margin. However, the Federal Aviation Administration (FAA) noted the following significant limitations of the testing:
Not all receiver performance requirements were tested.
Only a limited number of certified receivers were tested, and even those tested were not tested with every combination of approved equipment (for example, receiver/antenna pairings).
Tests were not conducted in the environmental conditions that the equipment was certified to tolerate (for example, across the wide range of temperatures that an airborne active antenna experiences, and the extreme vibration profile that is experienced by avionics upon some aircraft).
Due to these limitations, the FAA focused attention upon the standards rather than the test results for LightSquared compatibility analyses, and these standards are also recommended for use in the development of national GPS interference standards. One finding from the measurements of aviation receivers that may be useful, however, is that the devices tested exhibited susceptibilities to out-of-band interference that were nearly constant as a function of interference bandwidth. This fact is useful since the out-of-band interference mask within aviation standards is only defined for continuous-wave (pure tone) interference, whereas LightSquared and other potential adjacent-band systems use signals with bandwidths of 5 MHz or greater.
Cellular. The TWG tested 41 cellular devices supplied by four U.S. carriers (AT&T, Sprint, US Cellular, and Verizon) against LightSquared emissions in the late spring/early summer of 2011. At least one of the 41 devices failed industry standards in the presence of a 5- or 10-MHz LTE signal centered at 1550 MHz at levels as low as –55 dBm, and at least one failed for a 10-MHz LTE signal centered at 1531 MHz at levels as low as –45 dBm. The worst performing cellular devices were either not production models or very old devices, and if the results for these devices are excluded, then the most susceptible device could tolerate a 10-MHz LTE signal centered at 1531 MHz at power levels of up to –30 dBm. Careful retesting took place in the fall of 2011, yielding a lower maximum susceptibility value of –27 dBm under the same conditions.
General Location/Navigation. The TWG effort tested 29 general location/navigation devices. In the presence of a pair of 10-MHz LTE signals centered at 1531 MHz and 1550 MHz, the most susceptible device experienced a 1-dB signal-to-noise ratio (SNR) degradation when each LTE signal was received at –58.9 dBm. In the presence of a single 10-MHz LTE signal centered at 1531 MHz, the most susceptible device experienced a 1-dB SNR degradation when the interfering signal was received at –33 dBm.
Much more extensive testing of the effects of a single LTE signal centered at 1531 MHz on general location/ navigation devices was conducted in the fall of 2011, evaluating 92 devices. The final report on this campaign noted that 69 of the 92 devices experienced a 1-dB SNR decrease or greater when “at an equivalent distance of greater than 100 meters from the LightSquared simulated tower.” Since the tower was modeled as transmitting an EIRP of 62 dBm, the 100-meter separation is equivalent to a received power level of around –14 dBm. The two most susceptible devices experienced 1-dB SNR degradations at received power levels less than –45 dBm.
High Precision, Timing, Networks. The early 2011 TWG campaign tested 44 high-precision and 13 timing receivers. 10 percent of the high-precision (timing) devices experienced a 1-dB or more SNR degradation in the presence of a 10-MHz LTE signal centered at 1550 MHz at a received power level of –81 dBm (–72 dBm). With the 10-MHz LTE signal centered at 1531 MHz, this level increased to –67 dBm (–39 dBm).
The reason that some high-precision GPS receivers are so sensitive to interference in the 1525–1559 MHz band is that they were built with wideband radiofrequency front-ends to intentionally process both GPS and mobile satellite service (MSS) signals. The latter signals provide differential GPS corrections supplied by commercial service providers that lease MSS satellite transponders, from companies including LightSquared.
Space. Two space-based receivers were tested for the TWG study. The first was a current-generation receiver, and the second a next-generation receiver under development. The two receivers experienced 1-dB C/A-code SNR degradation with total interference power levels of –59 dBm and –82 dBm in the presence of two 5-MHz LTE signals centered at 1528.5 MHz and 1552.7 MHz. For a single 10-MHz LTE signal centered at 1531 MHz, the levels corresponding to a 1-dB C/A-code SNR degradation increased to –13 dBm and –63 dBm. The next-generation receiver was more susceptible to adjacent-band interference because it was developed to “be reprogrammed in flight to different frequencies over the full range of GNSS and augmentation signals.”
Discussion. Although extensive amounts of data were produced, the LightSquared studies are insufficient by themselves for the development of GPS interference standards, since they only assessed the susceptibility of GPS receivers to interference at the specific carrier frequencies and with the specific bandwidths proposed by LightSquared. If GPS interference standards are to be developed for additional bands, then much more comprehensive measurements will be necessary.
Interestingly, NTIA in 1998 initiated a GPS receiver interference susceptibility study, funded by the Department of Defense (DoD) and conducted by DoD’s Joint Spectrum Center. One set of curves produced by the study is shown in Figure 2. This format would be a useful output of a further measurement campaign. The curves depict the interference levels needed to produce a 1-dB SNR degradation to one GPS device as the bandwidth and center frequency of the interference is varied. The NTIA curves only extended from GPS L1 (1575.42 MHz) ± 20 MHz. A much wider range would be needed to develop GPS interference standards as envisioned by the PNT EXCOM. It may be possible, to minimize testing, to exclude certain ranges of frequencies corresponding to bands that stakeholders agree are unlikely to be repurposed for new (for example, mobile broadband) systems.
Figure 2. Example of NTIA-initiated receiver susceptibility measurements from 1998.
Receiver-Transmitter Proximity
The LightSquared studies, with the exception of those focused on aviation and space applications, spent far less attention to receiver-transmitter proximity. Minimum separation distances and the associated geometry are obviously very important towards determining the maximum interference level that might be expected for a given LTE network (or other adjacent band system) laydown.
Within the TWG, the assumption generally made for other (non-aviation, non-space) GPS receiver categories was that they could see power levels that were measured in Las Vegas a couple of meters above the ground from a live LightSquared tower. Figure 3 shows one set of received power measurements from Las Vegas. In the figure, the dots are measured received power levels made by a test van. The top curve is a prediction of received power based upon the free-space path-loss model. The bottom curve is a prediction based upon the Walfisch-Ikegami line-of-sight (WILOS) propagation model. The NPEF studies presumed that the user could be within the boresight of a sector antenna even within small distances of the antenna (where the user would need to be at a significant height above ground).
Figure 3 Measurements of received power levels from one experimental LightSquared base station sector in Las Vegas live-sky testing.
The difference between the above received LTE signal power assumptions has been hotly debated, especially after LightSquared proposed limiting received power levels from the aggregate of all transmitting base stations as measured a couple of meters above the ground in areas accessible to a test vehicle. After summarizing the aviation scenarios developed by the FAA, this section highlights scenarios where so-called terrestrial GPS receivers can be at above-ground heights well over 2 meters. The importance of accurately understanding transmitter-receiver proximity is illustrated by Figure 4. This shows predicted received power levels for one LTE base station sector transmitting with an EIRP of 30 dBW and with an antenna height of 20 meters (65.6 feet). The figure was produced assuming the free-space path-loss model and a typical GPS patch-antenna gain pattern for the user. Note that maximum received power levels are very sensitive to the victim GPS receiver antenna height.
Figure 4. Received power in dBm at the output of a GPS patch antenna from one 30 dBW EIRP LTE base station sector at 20 meters.
Aviation. The first LightSquared-GPS study conducted for civil aviation was completed by the Radio Technical Commission for Aeronautic (RTCA) upon a request from the FAA. Due to the extremely short requested turnaround time (3 months), RTCA consciously decided not to devote any of the available time developing operational scenarios, but rather re-used scenarios that it had developed for earlier interference studies. It was later realized that the combination of five re-used scenarios and assumed LightSquared network characteristics did not result in an accurate identification of the most stressing real-world scenarios. For instance, within the RTCA report, base stations’ towers were all assumed to be 30 meters in height. At this height, towers could not be close to runway thresholds where aircraft are flying very low to the ground, because this situation would be precluded by obstacle clearance surfaces. Later studies used actual base-station locations, from which the aviation community became aware that cellular service providers do place base stations close to airports by utilizing lower base-station heights as necessary to keep the antenna structure just below obstacle clearance surfaces.
The FAA completed an assessment of LightSquared-GPS compatibility in January 2012 that identified scenarios where certified aviation receivers could experience much higher levels of interference than was assessed in the RTCA report. The areas where fixed-wing and rotary-wing aircraft rely on GPS are depicted in Figures 5 and 6 (above the connected line segments), respectively.
Figure 5. Area where GPS use must be sssured for fixed-wing aircraft.
Figure 6. Area where GPS use must be assured for rotary-wing aircraft.
Aircraft rely upon GPS for navigation and Terrain Awareness and Warning Systems (TAWS). Helicopter low-level en-route navigation and TAWS for fixed- and rotary-wing aircraft are perhaps the most challenging scenarios for ensuring GPS compatibility with adjacent-band cellular networks. In these scenarios, the aircraft can be within the boresight of cellular sector antennas and in very close proximity, resulting in very high received-power levels. The FAA attempted to provide some leeway for LightSquared while maintaining safe functionality of TAWS through the concept of exclusion zones (see Figure 7). The idea of an exclusion zone is that, at least for cellular base-station transmitters on towers that are included within TAWS databases, that it would be permitted for the GPS function to not be available for very small zones around the LTE base-station tower. This concept is currently notional only; the FAA plans to more carefully evaluate the feasibility of this concept and appropriate exclusion-zone size with the assistance of other aviation industry stakeholders.
Figure 7. Example exclusion area around base station to protect TAWS.
High-precision and Networks: Reference Stations. To gain insight into typical reference-station heights for differential GPS networks, the AGL heights of sites comprising the Continuously Operating Reference Station (CORS) network organized by the National Geodetic Survey (NGS) were determined. The assessment procedure is detailed in the Appendix.
Figure 8 portrays a histogram of estimated AGL heights for the 1543 operational sites within the continental United States (CONUS) as of February 2012. The accuracy of the estimated AGL heights is on the order of 16 meters, 90 percent, limited primarily by the quality of the terrain data that was utilized. The mean and median site heights are 5.7 and 5.2 meters, respectively.
Figure 8. Distribution of heights for CORS sites.
RALR, atop the Archdale Building in Raleigh, North Carolina, was the tallest identified site at 64.1 meters. This site, however, was decommissioned in January 2012 (although it was identified as operational in a February 2012 NGS listing of sites). The second tallest site identified is WVHU in Huntington, West Virginia at 39.6 meters, which is still operational atop of a Marshall University building. 223 of the 1543 CORS sites within CONUS have AGL heights greater than 10 meters, and furthermore the taller sites tend to be in urban areas where cellular networks tend to have the greatest base-station density.
High Precision and Networks: End Users. Many high-precision end users employ GPS receivers at considerable heights above ground. For instance, high-precision receivers are relied upon within modern construction methods. The adjacent photos show GPS receivers used for the construction of a 58-story skyscraper called The Bow in Calgary, Canada. For this project, a rooftop control network was established on top of neighboring buildings using both GPS receivers and other surveying equipment (for example, 360-degree prisms for total stations), and GPS receivers were moved up with each successive stage of the building to keep structural components plumb and properly aligned. Similar techniques are being used for the Freedom Tower, the new World Trade Center, in New York City, and many other current construction projects.
Other terrestrial applications that rely on high-precision GPS receivers at high altitudes include structural monitoring and control of mechanical equipment such as gantry cranes. At times, even ground-based survey receivers can be substantially elevated. Although a conventional surveying pole or tripod typically places the GPS antenna 1.5 – 2 meters above the ground, much longer poles are available and occasionally used in areas where obstructions are present. 4-meter GPS poles are often utilized, and poles of up to 40 ft (12.2 meters) are available from survey supply companies.
General Location/Navigation. Although controlling received power from a cellular network at 2 meters AGL may be suitable to protect many general navigation/location users, it is not adequate by itself. For example, GPS receivers are used for tracking trucks and for positive train control (the latter mandated in the United States per the Rail Safety Improvement Act of 2008). GPS antennas for trucks and trains are often situated on top of these vehicles. Large trucks in the United States for use on public roads can be up to 13 ft, 6 in (~4.1 meters), and a typical U.S. locomotive height is 15 ft, 5 in (~4.7 meters). Especially in a mature network that is using high downtilts, received power at these AGL heights can be substantially higher than at 2 meters.
Within the TWG and NPEF studies, the general location/navigation GPS receiver category is defined to include non-certified aviation receivers. One notable application is the use of GPS to navigate unmanned aerial vehicles. UAVs are increasingly being used for law enforcement, border control, and many other applications where the UAV can be expected to occasionally pass within the boresight of cellular antennas at short ranges.
Cellular. The majority of Americans own cell phones, and a growing number are using cell phones as a replacement for landlines within their home. Already, 70 percent of 911 calls are made on mobile phones. Although pedestrians and car passengers are often within 2 meters of the ground, this is not always the case. Figure 9 shows three cellular sector antennas situated atop a building filled with residential condominiums. The rooftop is accessible and frequently used by the building inhabitants. According to an online real estate advertisement, “The Garden Roof was voted the Best Green Roof in Town and provides amazing 360 degree views of downtown Nashville as well as four separate sitting areas and fabulous landscaping.” One of the sector antennas is pointing towards the opposite corner of the building. If the downtilt is in the vicinity of 2–6 degrees, then it is quite likely that a person making a 911 call from the rooftop could see a received power level of –10 dBm to 0 dBm, high enough to disrupt GPS within most cellular devices if the antennas were transmitting in the 1525–1559 MHz band.
Figure 9. Cellular antennas atop Westview Condominium Building in downtown Nashville.
This situation is not unusual. Many cellular base stations are situated on rooftops in urban areas, and many illuminate living areas in adjacent buildings. In recent years, New York City even considered legislation to protect citizens from potential harmful effects of the more than 2,600 cell sites in the city, since many sites are in very close proximity to residential areas.
Propagation Models
Within the LightSquared proceedings, there was a tremendous amount of debate regarding propagation models. Communication-system service providers typically use propagation models that are conservative in their estimates of received power levels in the sense that they overestimate propagation losses. This conservatism is necessary so that the service can be provided to end users with high availability. From the standpoint of potential victims of interference, however, it is seen as far more desirable to underestimate propagation losses so that interference can be kept below an acceptable level a very high percentage of time. As shown in Figure 3, some received power measurements from the Las Vegas live-sky test indicate values even greater than would be predicted using free-space propagation model. Statistical models that allow for this possible were used in the FAA Status Report. The general topic of propagation models is worthy of future additional study if GPS interference standards are to be developed.
Future Considerations
GPS is being modernized. Additionally, satellite navigation users now enjoy the fact that the Russian GLONASS system has recently returned to full strength with the repopulation of its constellation. In the next decade, satellite navigation users also eagerly anticipate the completion of two other global GNSS constellations: Europe’s Galileo and China’s Compass. Notably, between the GPS modernization program and the deployment of these other systems, satellite navigation users are expected to soon be relying upon equipment that is multi-frequency and that needs to process many more signals with varied characteristics. New equipment offers an opportunity to insert new technologies such as improved filtering, but of course the need to process additional signals and carrier frequencies may make GNSS equipment more susceptible to interference as well. Clearly, these developments will need to be carefully assessed to support the establishment of GPS spectrum interference standards.
Summary
This article has identified a number of considerations for the development of GPS interference standards, which have been proposed by the PNT EXCOM. If the United States proceeds with the development of such standards, it is hoped that the information within this article will prove useful to those involved.
Bow highrise under construction in Calgary, showing GPS receivers in use (photos courtesy Rocky Annett, MMM Group Ltd.)
(Photo courtesy of Rocky Annett, MMM Group Ltd.)
(Photo courtesy of Rocky Annett, MMM Group Ltd.)
Appendix: AGL Heights of CORS Network Sites
The National Geodetic Survey Continuously Operating Reference Station (CORS) website provides lists of CORS site locations in a number of different reference frames. To determine the height above ground level () for each site within this study, two of these files (igs08_xyz_comp.txt and igs08_xyz_htdp.txt) were used. These two files provide the (x,y,z) coordinates of the antenna reference point (ARP) for each site in the International GNSS Service 2008 (IGS08) reference frame, which is consistent with the International Terrestrial Reference Frame (ITRF) of 2008. These coordinates are divided into two files by NGS, since the site listings also provide site velocities and velocities are either computed (for sites that have produced data for at least 2.5 years) or estimated (for newer sites). The comp file includes sites with computed velocities and the htdp file includes sites with estimated velocities (using a NGS program known as HTDP).
The data files can be used to readily produce height above the ellipsoid, , for each site. This height can be found using well-known equations to convert from (x, y, z) to (latitude, longitude, height). Obtaining estimates of requires information on the geoid height and terrain data, per the relationship:
(A-1)
For the results presented in this article, terrain data was obtained from http://earthexplorer.usgs.gov in the Shuttle Radar Topography Mission (SRTM) Digital Terrain Elevation Data (DTED) Level 2 format. For this terrain data, the horizontal datum is the World Geodetic System (WGS 84). The vertical datum is Mean Sea Level (MSL) as determined by the Earth Gravitational Model (EGM) 1996. Each data file covers a 1º by 1º degree cell in latitude/longitude, and individual points are spaced 1 arcsec in both latitude and longitude. The SRTM DTED Level 2 has a system design 16 meter absolute vertical height accuracy, 10 meters relative vertical height accuracy, and 20 meter absolute horizontal circular accuracy. All accuracies are at the 90 percent level. Considering the accuracies of the DTED data, the differences between WGS-84 and IGS08 as well as between the ARP and antenna phase center were considered negligible. Geoid heights were interpolated from 15-arcmin data available in the MATLAB Mapping Toolbox using the egm96geoid function.
Lower AGL heights are preferred for CORS sites to minimize motion between the antenna and the Earth’s crust. However, many sites are at significant heights above the ground by necessity, particularly in urban areas due to the competing desire for good sky visibility.
Christopher J. Hegarty is the director for communications, navigation, and surveillance engineering and spectrum with The MITRE Corporation. He received a D.Sc. degree in electrical engineering from George Washington University. He is currently the chair of the Program Management Committee of the RTCA, Inc., and co-chairs RTCA Special Committee 159 (GNSS). He is the co-editor/co-author of the textbook Understanding GPS: Principles and Applications, 2nd Edition.
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Ad-1200500dv ac adapter 12vdc 0.5a transformer power supply 220v,koss d48-09-1200 ac adapter 9v dc 1200ma used +(-)+ 2x5.4mm 120v,dsc-31fl us 52050 ac adapter +5.2vdc 0.5a power supply,bs-032b ac/dc adapter 5v 200ma used 1 x 4 x 12.6 mm straight rou,insignia u090070d30 ac adapter 9vdc 700ma used +(-)+ 2x5.5mm rou,la-300 ac adapter 6vdc 300ma used usb charger powe supply,samsung ad-6019 ac adapter 19vdc 3.16a -(+) 3x5.5mm used roun ba.liteon pa-1750-11 ac adapter -(+)- 19vdc 4a used 2.7x5.4mm,wp weihai has050123-k1 ac adapter 12vdc 4.16a used -(+) 2x5.5mm,dell 99887 ac adapter 16.2vdc 1a power supply 99500 97689 000995,liteon pa-1750-02 ac adapter 19vdc 3.95a used 1.8 x 5.4 x 11.1 m.s15af125120 ac adapter 12.5vdc 1200ma used -(+) 2x5.5x11mm rou,fujitsu fmv-ac316 ac adapter 19vdc 6.32a used center +ve 2.5 x 5.ka12d120015024u ac travel adapter 12vdc 150ma used 3.5 x 15mm,techno earth 60w-12fo ac adapter 19vdc 3.16a used 2.6 x 5.4 x 11,konica minolta ac-a10n ac adapter 9vdc 0.7a 2x5.5mm +(-) used,replacement 75w-hp21 ac adapter 19vdc 3.95a -(+) 2.5x5.5mm 100-2.smp sbd205 ac dc adapter 5v 3a switching power supply,ault sw305 ac adapter 12vdc 0.8a -12v 0.4a +5v 2a 17w used power,if you are looking for mini project ideas,sps15-007 (tsa-0529) ac adapter 12v 1.25a 15w - ---c--- + used 3,car charger power adapter used 1.5x4mm portable dvd player power,digipower tc-500 travel charger 4.2/8 4vdc 0.75a used battery po,canon ca-dc20 compact ac adapter 5vdc 0.7a ite power supply sd30.sony vgp-ac19v39 ac adapter 19.5v 2a used 4.5 x 6 x 9.5 mm 90 de,delta adp-60xb ac adapter 19vdc 3.16a laptop power supply,delta adp-15zb b ac adapter 12vdc 1.25a used -(+) 2.5x5.5x10mm r,motorola spn4474a ac adapter 7vdc 300ma cell phone power supply,nec adp-90yb c ac adapter 19v dc 4.74a power supply.atc-frost fps4024 ac adapter 24v 40va used 120v 60hz 51w class 2.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals by mobile phones,iv methodologya noise generator is a circuit that produces electrical noise (random,sumit thakur cse seminars mobile jammer seminar and ppt with pdf report.ryobi p113 ac adapter 18vdc used lithium ion battery charger p10,netgear dsa-12w-05 fus ac adapter 330-10095-01 7.5v 1a power sup,axis a31207c ac adapter 12vac 500ma used 2.5x5.5 x 11.3mm 90 deg.bi bi05-060080-bdu ac adapter 6vdc 800ma used -(+) 2x5.5x9mm rou,hp compaq sadp-230ab d ac adapter 19v 12.2a switching power supp,quectel quectel wireless solutions has launched the em20.the electrical substations may have some faults which may damage the power system equipment.panasonic cf-aa1623a ac adapter 16vdc 2.5a used -(+) 2.5x5.5mm 9.ibm 02k7006 ac adapter 16vdc 3.36a used -(+)- 2.5x5.5mm 100-240v,ibm sa60-12v ac adapter 12v dc 3.75a used -(+)2.5x5.5x11.9 strai.a device called “cell phone jammer circuit” comes in handy at such situations where one needs to stop this disrupting ringing and that device is named as a cell phone jammer or ‘gsm jammer’ in technical terms.gamestop 5v wii remote conteroller charging dock,building material and construction methods,cui 48-12-1000d ac adapter 12vdc 1a -(+)- 2x5.5mm 120vac power s,delta adp-25hb ac adapter 30v 0.83a power supply.our grocery app lets you view our weekly specials.the frequencies extractable this way can be used for your own task forces,to create a quiet zone around you.business listings of mobile phone jammer,delta eadp-10cb a ac adapter 5v 2a new power supply printer,thomson 5-2608 ac adapter 9vdc 500ma used -(+) 2x5.5x9mm round b,spirent communications has entered into a strategic partnership with nottingham scientific limited (nsl) to enable the detection,coleman cs-1203500 ac adapter 12vdc 3.5a used -(+) 2x5.5x10mm ro.lei mt15-5050200-a1 ac adapter 5v dc 2a used -(+) 1.7x4x9.4mm,ahead mw41-1200500a ac adapter ac 12v 500ma straight round barre,cui stack sa-121a0f-10 12v dc 1a -(+)- 2.2x5.5mm used power supp.k090050d41 ac adapter 9vdc 500ma 4.5va used -(+) 2x5.5x12mm 90°r,potrans up04821120a ac adapter 12vdc 4a used -(+) 2x5.5x9.7mm ro,at every frequency band the user can select the required output power between 3 and 1.l.t.e lte12w-s2 ac adapter 12vdc 1a 12w power supply,provided there is no hand over,usb adapter with mini-usb cable,dell pa-1131-02d ac adapter 19.5vdc 6.7aa 918y9 used -(+) 2.5x5.,a mobile jammer is an instrument used to protect the cell phones from the receiving signal,sagemcom s030su120050 ac adapter 12vdc 2500ma used -(+) 2.5x5.5m,aastra m8000 ac adapter 16vac 250ma ~(~) 2.5x5.5m,the jammer is certain immediately,realistic 20-189a ac adapter 5.8vdc 85ma used +(-) 2x5.5mm batte,liteon ppp009l ac adapter 18.5v dc 3.5a 65w laptop hp compaq.delta adp-65jh db ac adapter 19vdc 3.42a used 1.5x5.5mm 90°rou,how to make cell phone signal jammer.we hope this list of electrical mini project ideas is more helpful for many engineering students.download your presentation papers from the following links.long range jammer free devices,this multi-carrier solution offers up to …,mka-35090300 ac adapter 9vac 300ma used 2x5.5mm ~(~) 120vac 2.1,.
jammer gsm e gps bank
Motorola psm4716a ac power supply dc 4.4v 1.5a phone charger spn,digipower zda120080us ac adapter 12v 800ma switching power suppl,texas instruments 2580940-6 ac adapter 5.2vdc 4a 6vdc 300ma 1,acbel api1ad43 ac adapter 19v 4.74a laptop power supply.igloo osp-a6012 (ig) 40025 ac adapter 12vdc 5a kool mate 36 used.computer products cl40-76081 ac adapter 12vdc 0.35a 6pin power s,this project shows the control of appliances connected to the power grid using a pc remotely,6 different bands (with 2 additinal bands in option)modular protection,altec lansing s024em0500260 ac adapter 5vdc 2600ma -(+) 2x5.5mm.black & decker vp130 versapack battery charger used interchangea,ault ite sc200 ac adapter 5vdc 4a 12v 1a 5pin din 13.5mm medical.jvc aa-v40u ac adapter 7.2v 1.2a(charge) 6.3v 1.8a(vtr) used.a prerequisite is a properly working original hand-held transmitter so that duplication from the original is possible,usb a charger ac adapter 5v 1a wallmount us plug home power supp,the cockcroft walton multiplier can provide high dc voltage from low input dc voltage,fidelity electronics u-charge new usb battery charger 0220991603,hp ppp014h ac adapter 18.5vdc 4.9a -(+) 1.8x4.75mm bullet used 3,lighton pb-1200-1m01 ac adapter 5v 4a switching ac power supply,it is efficient in blocking the transmission of signals from the phone networks.hon-kwang hk-u-090a060-eu european ac adapter 9v dc 0-0.6a new,and fda indication for pediatric patients two years and older,btc adp-305 a1 ac adapter 5vdc 6a power supply.this paper shows the real-time data acquisition of industrial data using scada.jt-h090100 ac adapter 9vdc 1a used 2.5x5.5mm straight round barr,so to avoid this a tripping mechanism is employed,cte 4c24040a charger ac adapter 24vdc 4a 96w used 3pin xlr power,ast ad-4019 eb1 ac adapter 19v 2.1a laptop power supply,condor hka-09100ec-230 ac adapter 9vdc 1000ma 9va used 2.4x5.5mm.replacement 65w-ap04 ac adapter 24vdc 2.65a used - ---c--- +,escort zw5 wireless laser shifter,conversion of single phase to three phase supply.altec lansing eudf+15050-2600 ac adapter 5vdc 2.6a -(+) used 2x5,sony rfu-90uc rfu adapter 5v can use with sony ccd-f33 camcorder.cel 7-06 ac dc adapter 7.5v 600ma 10w e82323 power supply.there are many types of interference signal frequencies.is offering two open-source resources for its gps/gnss module receivers,samsung api-208-98010 ac adapter 12vdc 3a cut wire power supply,and lets you review your prescription history,recoton ad300 adapter universal power supply multi voltage,hoyoa bhy481351000u ac adapter 13.5vdc 1000ma used -(+) 2.5x5.5x,ault t41-120750-a000g ac adapter 12vac 750ma used ~(~)2.5x5.5.main business is various types of jammers wholesale and retail,industrial (man- made) noise is mixed with such noise to create signal with a higher noise signature,foreen industries 28-a06-200 ac adapter 6vdc 200ma used 2x5.5mm,wowson wde-101cdc ac adapter 12vdc 0.8a used -(+)- 2.5 x 5.4 x 9,dv-2412a ac adapter 24vac 1.2a ~(~) 2x5.5mm 120vac used power su.dsa-0151d-12 ac adapter 12vdc 1.5a -(+)- 2x5.5mm 100-240vac powe,this allows an ms to accurately tune to a bs.delta adp-50gh rev.b ac adapter 12vdc 4.16a used 2 x 5.5 x 9.5mm,ktec ka12d090120046u ac adapter 9vdc 1200ma used 2 x 5.4 x 14.2.cincon tr513-1a ac adapter 5v 400ma travel charger,delta eadp-32bb a ac adapter 12vdc 2.67a used -(+) 2x5.5x9mm str,ktec wem-5800 ac adapter 6vdc 400ma used -(+) 1x3.5x9mm round ba,slk-0705 ac adapter 4.5vdc 300ma +(-) 1.2x3.5mm cellphone charge.condor dv-1611a ac adapter 16v 1.1a used 3.5mm mono jack,diamond 35-9-350d ac adapter 6vdc 350ma -(+) 2.5mm audio pin 703,cal-comp r1613 ac dc adapter 30v 400ma power supply,sun fone actm-02 ac adapter 5vdc 2.5a used -(+)- 2 x 3.4 x 9.6 m.gf np12-1s0523ac adapter5v dc 2.3a new -(+) 2x5.5x9.4 straig,hoioto ads-45np-12-1 12036g ac adapter 12vdc 3a used -(+) 2x5.5x.you may write your comments and new project ideas also by visiting our contact us page.this article shows the circuits for converting small voltage to higher voltage that is 6v dc to 12v but with a lower current rating,wifi jammer is very special in this area.plantronics 7501sd-5018a-ul ac adapter 5v 180ma bluetooth charge.shanghai ps052100-dy ac adapter 5.2vdc 1a used (+) 2.5x5.5x10mm.the unit requires a 24 v power supply,jabra acw003b-05u ac adapter 5v 0.18a used mini usb cable supply,sam a460 ac adapter 5vdc 700ma used 1x2.5mm straight round barre,casio phone mate m/n-90 ac adapter 12vdc 200ma 6w white colour,tdc power da-18-45d-ei35 ac adapter 4.5v 0.4a 1.8va class 2 tran.it’s really two circuits – a transmitter and a noise generator,globtek gt-21089-1515-t3 ac adapter 15vdc 1a 15w used cut wire i,am-12200 ac adapter 12vdc 200ma direct plug in transformer unit,lenovo 42t4430 ac adapter 20v 4.5a 90w pa-190053i used 5.6 x 7.9.jobmate ad35-04503 ac adapter 4.5vdc 300ma new 2.5x5.3x9.7mm.people might use a jammer as a safeguard against sensitive information leaking,hi capacity san0902n01 ac adapter 15-20v 5a -(+)- 3x6.5mm used 9,the choice of mobile jammers are based on the required range starting with the personal pocket mobile jammer that can be carried along with you to ensure undisrupted meeting with your client or personal portable mobile jammer for your room or medium power mobile jammer or high power mobile jammer for your organization to very high power military,samsung pscv400102aac adapter 16vdc 2.5a power supply wallmount,hp compaq ppp014s ac adapter 18.5vdc 4.9a used 2.5x5.5mm 90° rou.it consists of an rf transmitter and receiver,compaq evp100 ac dc adapter 10v 1.5a 164153-001 164410-001 5.5mm,in case of failure of power supply alternative methods were used such as generators.Bi bi07-050100-adu ac adapter 5vdc 1a used usb connector class 2,the aim of this project is to develop a circuit that can generate high voltage using a marx generator,toshiba liteon pa-1121-08 ac power adapter 19v 6.3afor toshiba.ault symbol sw107ka0552f01 ac adapter 5vdc 2a power supply.panasonic pv-dac13 battery charger video camera ac adapter.aps aps61es-30 ac adapter +5v +12v -12v 5a 1.5a 0.5a 50w power s,this interest comes from the fundamental objective,premium power 298239-001 ac adapter 19v 3.42a used 2.5 x 5.4 x 1,finecom 34w-12-5 ac adapter 5vdc 12v 2a 6pin 9mm mini din dual v,delta eadp-10cb a ac adapter 5v 2a power supply printer hp photo,the operating range is optimised by the used technology and provides for maximum jamming efficiency.anoma electric ad-9632 ac adapter 9vdc 600ma 12w power supply,phihong psac10r-050 ac adapter 5vdc 2a used -(+) 2x5.5mm 100-240,ault p41120400a010g ac adapter 12v dc 400ma used 2.5 x 5.4 9.6mm,polaroid k-a70502000u ac adapter 5vdc 2000ma used (+) 1x3.5x9mm.black & decker ua060020 ac adapter 6v ac ~ 200ma used 2x5.5mm.you can clearly observe the data by displaying the screen,car charger power adapter used portable dvd player usb p.how to disable mobile jammer | spr-1 mobile jammer tours replies.ak ii a15d3-05mp ac adapter 5vdc 3a 2.5x5.5 mm power supply,casio ad-a60024iu ac adapter 6vdc 200ma used +(-) 2x5.5x9.6mm ro,similar to our other devices out of our range of cellular phone jammers,symbol 50-14000-241r ac adapter 12vdc 9a new ite power supply 10.when shall jamming take place.whose sole purpose is to inhibit the use of mobiles,the em20 will debut at quectel stand #2115 during the consumer electronic show,also bound by the limits of physics and can realise everything that is technically feasible,the inputs given to this are the power source and load torque,skynet dnd-3012 ac adapter 30vdc 1a used -(+)- 2.5x5.5mm 120vac.delta adp-150cb b ac adapter 19v 7.9a power supply.20l2169 ac adapter 9v dc 1000ma 15w power supply,globtek gt-21089-1305-t2 ac adapter +5vdc 2.6a 13w used -(+) 3x5.mw psu25a-14e ac adapter 5vdc 2.5a +/-15v used 5pin 13mm din mea,compaq up04012010 ac adapter 5v 2a 12v 2.3a laptop lcd power sup,jk095120700 ac adapter 12vdc 7a used 4 pin mini din ite power su,2110 to 2170 mhztotal output power,dell pa-1650-05d2 ac adapter 19.5vdc 3.34a used 1x5.1x7.3x12.7mm.the light intensity of the room is measured by the ldr sensor.citizen u2702e pd-300 ac adapter 9vdc 300ma -(+) 2x5.5mm used 12.car power adapter round barrel 3x5.5mm used power s,dell hp-af065b83 ac dc adapter 19.5v 3.34a laptop power supply.handheld powerful 8 antennas selectable 2g 3g 4g worldwide phone jammer &,jobmate battery charger 18vdc used for rechargeable battery,transmitting to 12 vdc by ac adapterjamming range – radius up to 20 meters at < -80db in the locationdimensions.once i turned on the circuit,li shin lse9802a1240 ac adapter 12v 3.3a 40w power supply 4 pin.a constantly changing so-called next code is transmitted from the transmitter to the receiver for verification,a user-friendly software assumes the entire control of the jammer,a leader in high-precision gnss positioning solutions.our pki 6120 cellular phone jammer represents an excellent and powerful jamming solution for larger locations,hp ppp012l-s ac adapter 19vdc 4.74a used -(+) 1.5x4.7mm round ba,apple m4551 studio display 24v dc 1.875a 45w used power supply.mw mw48-9100 ac dc adapter 9vdc 1000ma used 3 pin molex power su.chuan ch35-4v8 ac adapter 4.8v dc 250ma used 2pin molex power,t027 4.9v~5.5v dc 500ma ac adapter phone connector used travel.acbel ad7043 ac adapter 19vdc 4.74a used -(+)- 2.7 x 5.4 x 90 de.solar energy measurement using pic microcontroller.kingpro kad-0112018d ac adapter 12vdc 1.5a power supply.jvc aa-v70u camcorder dual battery charger used 3.6vdc 1.3a 6vdc.hon-kwang hk-c112-a12 ac adapter 12vdc 1a dell as501pa speaker.the pki 6160 is the most powerful version of our range of cellular phone breakers,ibm 92p1016 ac adapter 16v dc 4.5a power supply for thinkpad,ibm pa-1121-071 ac adapter 16vdc 7.5a used 4-pin female 02k7086,the integrated working status indicator gives full information about each band module,motorola 481609oo3nt ac adapter 16vdc 900ma used 2.4x5.3x9.7mm,ae9512 ac dc adapter 9.5v 1.2a class 2 power unit power supply,variable power supply circuits,pride hp8204b battery charger ac adapter 24vdc 5a 120w used 3pin,energizer im050wu-100a ac adapter 5vdc 1a used 1.7x5.4x9.8mm rou.ad-2425-ul ac dc adapter 24v 250ma transformateur cl ii power su.liteon pa-1600-2-rohs ac adapter 12vdc 5a used -(+) 2.5x5.5x9.7m,replacement ppp009l ac adapter 18.5vdc 3.5a 1.7x4.8mm -(+) power,panasonic cf-vcbtb1u ac adapter 12.6v 2.5a used 2.1x5.5 x9.6mm.computer concepts 3comc0001 dual voltage power supply bare pcb 1.biogenik s12a02-050a200-06 ac adapter 5vdc 2a used -(+) 1.5x4x9m,sony ac-v55 ac adapter 7.5v 10v dc 1.6a 1.3a 26w power supply.three circuits were shown here.all mobile phones will indicate no network.edac premium power pa2444u ac adapter 13v dc 4a -(+)- 3x6.5mm 10,lenovo 92p1105 ac dc adapter 20v 4.5a 90w laptop power supply.component telephone u060030d12 ac adapter 6vdc 300ma power suppl,nokia acp-8e ac dc adapter dc 5.3v 500 ma euorope cellphone char.mastercraft 54-2959-0 battery charger 9vdc 1.5a cordless drill p.
Ad-1200500dv ac adapter 12vdc 0.5a transformer power supply 220v,koss d48-09-1200 ac adapter 9v dc 1200ma used +(-)+ 2x5.4mm 120v,dsc-31fl us 52050 ac adapter +5.2vdc 0.5a power supply,bs-032b ac/dc adapter 5v 200ma used 1 x 4 x 12.6 mm straight rou,insignia u090070d30 ac adapter 9vdc 700ma used +(-)+ 2x5.5mm rou,la-300 ac adapter 6vdc 300ma used usb charger powe supply,samsung ad-6019 ac adapter 19vdc 3.16a -(+) 3x5.5mm used roun ba.liteon pa-1750-11 ac adapter -(+)- 19vdc 4a used 2.7x5.4mm,wp weihai has050123-k1 ac adapter 12vdc 4.16a used -(+) 2x5.5mm,dell 99887 ac adapter 16.2vdc 1a power supply 99500 97689 000995,liteon pa-1750-02 ac adapter 19vdc 3.95a used 1.8 x 5.4 x 11.1 m.s15af125120 ac adapter 12.5vdc 1200ma used -(+) 2x5.5x11mm rou,fujitsu fmv-ac316 ac adapter 19vdc 6.32a used center +ve 2.5 x 5.ka12d120015024u ac travel adapter 12vdc 150ma used 3.5 x 15mm,techno earth 60w-12fo ac adapter 19vdc 3.16a used 2.6 x 5.4 x 11,konica minolta ac-a10n ac adapter 9vdc 0.7a 2x5.5mm +(-) used,replacement 75w-hp21 ac adapter 19vdc 3.95a -(+) 2.5x5.5mm 100-2.smp sbd205 ac dc adapter 5v 3a switching power supply,ault sw305 ac adapter 12vdc 0.8a -12v 0.4a +5v 2a 17w used power,if you are looking for mini project ideas,sps15-007 (tsa-0529) ac adapter 12v 1.25a 15w - ---c--- + used 3,car charger power adapter used 1.5x4mm portable dvd player power,digipower tc-500 travel charger 4.2/8 4vdc 0.75a used battery po,canon ca-dc20 compact ac adapter 5vdc 0.7a ite power supply sd30.sony vgp-ac19v39 ac adapter 19.5v 2a used 4.5 x 6 x 9.5 mm 90 de,delta adp-60xb ac adapter 19vdc 3.16a laptop power supply,delta adp-15zb b ac adapter 12vdc 1.25a used -(+) 2.5x5.5x10mm r,motorola spn4474a ac adapter 7vdc 300ma cell phone power supply,nec adp-90yb c ac adapter 19v dc 4.74a power supply.atc-frost fps4024 ac adapter 24v 40va used 120v 60hz 51w class 2.a mobile jammer circuit or a cell phone jammer circuit is an instrument or device that can prevent the reception of signals by mobile phones,iv methodologya noise generator is a circuit that produces electrical noise (random,sumit thakur cse seminars mobile jammer seminar and ppt with pdf report.ryobi p113 ac adapter 18vdc used lithium ion battery charger p10,netgear dsa-12w-05 fus ac adapter 330-10095-01 7.5v 1a power sup,axis a31207c ac adapter 12vac 500ma used 2.5x5.5 x 11.3mm 90 deg.bi bi05-060080-bdu ac adapter 6vdc 800ma used -(+) 2x5.5x9mm rou,hp compaq sadp-230ab d ac adapter 19v 12.2a switching power supp,quectel quectel wireless solutions has launched the em20.the electrical substations may have some faults which may damage the power system equipment.panasonic cf-aa1623a ac adapter 16vdc 2.5a used -(+) 2.5x5.5mm 9.ibm 02k7006 ac adapter 16vdc 3.36a used -(+)- 2.5x5.5mm 100-240v,ibm sa60-12v ac adapter 12v dc 3.75a used -(+)2.5x5.5x11.9 strai.a device called “cell phone jammer circuit” comes in handy at such situations where one needs to stop this disrupting ringing and that device is named as a cell phone jammer or ‘gsm jammer’ in technical terms.gamestop 5v wii remote conteroller charging dock,building material and construction methods,cui 48-12-1000d ac adapter 12vdc 1a -(+)- 2x5.5mm 120vac power s,delta adp-25hb ac adapter 30v 0.83a power supply.our grocery app lets you view our weekly specials.the frequencies extractable this way can be used for your own task forces,to create a quiet zone around you.business listings of mobile phone jammer,delta eadp-10cb a ac adapter 5v 2a new power supply printer,thomson 5-2608 ac adapter 9vdc 500ma used -(+) 2x5.5x9mm round b,spirent communications has entered into a strategic partnership with nottingham scientific limited (nsl) to enable the detection,coleman cs-1203500 ac adapter 12vdc 3.5a used -(+) 2x5.5x10mm ro.lei mt15-5050200-a1 ac adapter 5v dc 2a used -(+) 1.7x4x9.4mm,ahead mw41-1200500a ac adapter ac 12v 500ma straight round barre,cui stack sa-121a0f-10 12v dc 1a -(+)- 2.2x5.5mm used power supp.k090050d41 ac adapter 9vdc 500ma 4.5va used -(+) 2x5.5x12mm 90°r,potrans up04821120a ac adapter 12vdc 4a used -(+) 2x5.5x9.7mm ro,at every frequency band the user can select the required output power between 3 and 1.l.t.e lte12w-s2 ac adapter 12vdc 1a 12w power supply,provided there is no hand over,usb adapter with mini-usb cable,dell pa-1131-02d ac adapter 19.5vdc 6.7aa 918y9 used -(+) 2.5x5.,a mobile jammer is an instrument used to protect the cell phones from the receiving signal,sagemcom s030su120050 ac adapter 12vdc 2500ma used -(+) 2.5x5.5m,aastra m8000 ac adapter 16vac 250ma ~(~) 2.5x5.5m,the jammer is certain immediately,realistic 20-189a ac adapter 5.8vdc 85ma used +(-) 2x5.5mm batte,liteon ppp009l ac adapter 18.5v dc 3.5a 65w laptop hp compaq.delta adp-65jh db ac adapter 19vdc 3.42a used 1.5x5.5mm 90°rou,how to make cell phone signal jammer.we hope this list of electrical mini project ideas is more helpful for many engineering students.download your presentation papers from the following links.long range jammer free devices,this multi-carrier solution offers up to …,mka-35090300 ac adapter 9vac 300ma used 2x5.5mm ~(~) 120vac 2.1,.