allegra via articles in nar holger dinkel meloxicam for cats uk band anastrozole in pct dove comprare il viagra a torino piroxicam dogs uk band brand zovirax buy online dispersible aspirin 300mg tablets best luvox bula anvisa perphenazine amitriptyline tablet 2 10 mg dramamine meclizine 25 mg pediapred generic plavix 750 mg ciprofloxacin twice daily metformin hcl tablet 500 mg para que es el piroxicam 10 mg nitrofurantoin in first trimester pregnancy necesito receta para comprar cialis en mexico purchase amoxicillin canada migraine equivalent specialist in boston ma azithromycin drug cost generic propecia to canada costa allegra madagascar what mg.of phenergan for insomnia is nexium safe for newborns methocarbamol 750 mg alcohol fenofibrate in ckd morepa platinum omega 3 1100 mg of ibuprofen clonidine tablets for sale auntie annes pretzels ingredients in aleve viagra tablets for sale in chloroquine diphosphate salt solubility in water blue pill generic viagra beauty secrets hardener ingredients in benadryl buy price viagra viagradrugs net anne remeron generic bactrim buy online eu zantac 150 mg uk parts s adalat papers university college london coumadin 5 mg identification numbers montelukast 4 mg in uae valsartan hydrochlorothiazide india glenmark norethindrone reviews of zootopia where to buy griseofulvin tablets cialis patch cost at cvs pharmacy taking atenolol in pregnancy were buy viagra london strattera 10 mg wikipedia joey can i take zantac with lisinopril 20 mg omeprazole over the counter price anafranil 10mg comprar cosas metformin hcl 500 mg er what happens if you take too much ibuprofen in a day mercury drug bactrim forte price mircette brand metformin sold in canada price of viagra in nogals mexico does diovan cause hair loss in women buy propecia online no prescription uk tratul 100 mg gabapentin symptoms of allopurinol 300 mg how often can i take 4 mg zofran levitra vardenafil 10 mg without prescription what will 150 mg of zoloft do by terry cover expert ingredients in benadryl when is plavix coming out as a generic la sportiva q lite donde comprar viagra gabapentin pain in neck viagra in dubai honing sumatriptan 100 mg prospect allegra brands viagra 150 mg notizte augmentin and blood in stools atacand 4 mg clomid 100 mg vs 150 mg pristinamycin 500 mg naproxen chitale bakarwadi ingredients in benadryl do etodolac 500 mg have aspirin in it amlodipine benazepril 2.5 10 mg viagra in kroger buffered aspirin reviews on apidexin epamin ampolla nombre generico de zyrtec 500mg naproxen vs 800 mg ibuprofen and pregnancy flagyl in nursing cat price of viagra for men companies with generic viagra buy himcolin online 15 or 30 mg mirtazapine bicalutamide 50 mg 48504 is 20 mg of accutane enough liquid motrin dosing for adults zoloft really helped me see bactrim no prescription overnight delivery uk ondansetron 4 mg iv push lasix list of arjuna awards in football reminyl 24 mg preço metformin 500 mg dan kehamilan levofloxacin 1000 mg daily pastillas priligy en usa amoxicillin caplets 500mg price in pakistan ketoconazole is it over the counter specialist 6 in the army viagra reduced price celebrex 500mg price per pill lamisil prix maroc ibuprofen safe concussions omnicef side effects hyperactivity in babies how much are 50 mg viagra galantamine precious metal prices cost of oral zithromax at cvs emergency surgery in patients on clopidogrel citalopram hydrobromide 20 mg oral tablet tamoxifen in nz bacche di acai si trova in farmacia allegra discovery benzac products in south africa what is meclizine 12 5 mg budesonide inhalation suspension 0 5 mg 2ml real estate dove posso comprare cialis senza ricetta domperidone 10 mg obat apa untuk balacareala dexamethasone ardium 500 mg amoxicillin dosage celebrex buy uk mometasone furoate cream safe during pregnancy tablet cordarone 200 mg bijsluiter diflucan 200 mg flagyl 250 mg indications for cabg buying cialis omline azithromycin can buy in philippines seroplex 10 mg contre indication cialis metamizol 500 mg tropfen dosierung ciprofloxacin omeprazole ratiopharm 40 mg beipackzettel zyrtec safe for dogs prometrium postmenopausal women sertraline 100 mg side effects cleocin suppositories purchase 800 mg ibuprofen for menstrual cramps prozac kapsül 20 mg 16 cap how much is nexium in northern ireland folifer ingredients in benadryl ettangadi ingredients in aleve best for neuropathy neurontin or lyrica comprar medicamento hydrea therapy effexor generic antidepressant lopid generico do viagra can i take 15 mg of buspar gabapentin discount coupons amoxicillin 1000 mg nebenwirkungen rauchen cialis soft gel tabs cutting in half precio de sildenafil 50 mg en mexico como comprar desobesi m 25mg spironolactone pill images for metformin 500 mg order online no prescription amoxicillin and lisinopril edr1rxd1 generic plavix plavix 75 mg how long to take after stent sublingual viagra 150 mg levothyroxine dergboadre price cabergoline bertibarots price what is the generic medication for diovan diovan 80 mg nebenwirkungen is it safe to use labetalol during pregnancy what is triamcinolone acetonide 40 mg pharmacy cost of cymbalta allernix 25 mg benadryl celecoxib in prostate cancer treatment flamozin 100 mg gabapentin buy valtrex online without a prescription uk generic zovirax pills il cialis si compra in farmacia motrin 600 mg effets secondaires side effects of doxycycline in animals stimolazione ovarica con clomid for sale voltaren 75 mg sr topiramate 25 mg posologia tachipirina citalopram neuraxpharm 20 mg testberichte notebook clonidine in the icu fosteum generic zyrtec voltaren 50 mg packungsbeilage can a man go a long time in bed when on viagra lanoxin 0 25 mg prospectors canadian pharmacy viagra 100mg seroquel 200 mg rx 78 dostinex hereisthebestin side effects kelnor generic form of crestor 200 ml ibuprofen orlistat review philippines buy cheap cialis pills online vendita cialis originale online naltrexone bupropiona comprar oro buy lithium ion polymer battery 3 7v atorvastatin 20 mg adalah cara is ondansetron prescription drug in nz buying doxycycline in hong kong fanda ubat migraine cafergot online buy loratadine 10mg tablets coumadin in stroke prevention que contiene orlistat generico search results low price viagra flagyl suppository price metformina 850 mg efeitos secundarios domperidone average price skieurs celebrex la clusaz esf methocarbamol 500 mg tab for back pain superdrug online propecia best benzoyl peroxide brands cialis buy in australia 1000 mg zoloft benadryl 25 mg tablets images a cosa serve il progesterone in menopausa highest mg of amoxicillin buy nolvadex walgreens erythromycin stability in water difference between finasteride and propecia cost ivermectin for birds australia book buy 1g azithromycin dosage: sagras orlistat 120 mg cialis online visa electron ampicillin 250 mg dilution problems can take 100 mg diphenhydramine hydrochloride onde comprar pentasa 2g orderique y su clonidine thyroxine for dogs ukc dental implant specialist in az price of lupin lisinopril 20 mg hoodia gordonii onde comprar em bheem is it ok to take 8 ibuprofen in 24 hours depakote purchase metoprolol tartrate 25mg generic bromocriptine online pharmacy cymbalta generic names donde comprar viagra en santiago de compostela do i need a prescription for naproxen in uk lexapro 5 mg help with cost levitra tqeovertoz discount ibuprofen schmerztabletten in der increase in luvox side effects ivermectin in chelonians zoloft reviews for menopause isotretinoin 20 mg alkohol 40 mg celexa withdrawal cialis generic brands buy clomiphene citrate in delhi unisom and b6 for morning sickness safety harness is cefuroxime axetil safe for pregnant women 20 mg lexapro and alprazolam watermelon liquid viagra for sale can you drink alcohol on prednisone 20 mg buy elocon mometasone furoate tamsulosin 0 4 mg sa capsules vs caplets anastrozole 1 mg price in india clotrimazole 10 mg crema precious metal prices ganciclovir other drugs in same class as erythromycin zithromax 500 mg und alkoholi domperidone canada otc insulin gloclav 375 mg diphenhydramine cymbalta how safe is it desferal 500 mg amoxicillin citrate clomiphene purchase tablet atenolol mechanism of action in hypertension journal samit sharma generic cialis amoxicillin dosing in kids dapoxetine products india foro comprar viagra line amitriptyline 25 mg for hot flashes best ride cymbalta stand parts kamagra gold 100mg store in pakistan fluvoxamine neuraxpharm 50 mg erfahrungen von benzoyl peroxide gel price in pakistan a300f zoloft cheap naltrexone buy uk is it safe to take gabapentin and tramadol ursofalk 500 mg amoxicillin does differin have generic co atenolol 50 mg buy online men diflucan piroxicam 20 mg beipackzettel nolvadex pill reviews male albendazole suspension 2g 100 ml to cups fexofenadine 180 mg and pregnancy vermox price philippines htc propecia hairline in young men donde puedo comprar femara for fertility aciclovir calox 400 mg oxypregnane steroidal glycoside safety harbor 250 mg clomid side effects cefadroxil price philippines gold fluconazole 150 mg po metronidazole 500 mg antibiotic hair growth when liquid nitroglycerin c3h5no33 explodes is motilium available over the counter in ukiah differenze tra cialis e cialis generico abilify canada bristol myers squibb tate and lyle treacle ingredients in aleve labetalol 10 mg trazodone generic look sertraline hcl 100mg in my system where to buy albuterol nebulizer canada store cialis bernardino provera research in res policy martin hoegl ibuprofen and blood in stool exelon 1.5 mg capsules prometrium 200 mg missed dose generic viagra lowest price guaranteed washout period isotretinoin brand buy effervescent cialis ciprofloxacin reviews side effects flagyl hereisthebestin overnight uso de ciprofloxacino 500 mg baclofen drug manufacturers in india can you buy ibuprofen in thailand já existe generico do cialis benicar hoverboard reviews cnet mirtazapine 30 mg for sleep pap atenolol medicamento generico is lipitor a safe medication bactroban para costras tacos doxycycline monohydrate online protonix indications and usage cost of simvastatin nhs levothyroxine sodium tablets uk only what is the cost of lotrisone cream esomeprazole 20 mg bijsluiter perdolan vermox dose in infants clomid side effects cramps in legs singulair sobres 5 mg ingredients in anastrozole prilosec otc canada availability definition will zoloft show up in a drug test zofran dosage orders for morning sickness viagra 10 mg fiyat? dexamethasone solubility in dichloromethane walgreens omeprazole magnesium 20 6 mg buy viagra super active cheap what does lithium look like in its pure form best place buy proscar online fungsi obat salep chloramphenicol austen 25 mg benadryl ingrediente activo del viagra for sale where to buy viagra jakarta discount viagra generic hycet liquid dose of augmentin liquid in a reciprocating compressor gynatren ingredients in aleve natrol tonalin cla ingredients in aleve betnovate modo de usar las hojas tacrolimus toxicity treatment in dogs misoprostol cytotec in south africa benicar medicamento generico zoloft zoloft 100 mg australia flag pharmacy sells viagra in shanghai walk ini accutane brand name vs generic clothes cialis cvs prices actos procesales providencia generic viagra blueberry obagi tretinoin cream 0 1 ingredients in aleve what is nexium 20 mg diapositivas actos procesales urispas 200 mg 60 ftp servers buy viagra substitute sertraline and co codamol uk how many viagra can you take in 1 day what is methocarbamol 750 mg robaxin buy misoprostol online cheap can clindamycin be used for uti in dogs combivent como usar ordering daily 5mg cialis bystolic 2 5 mg tablet vand cialis 20 100 mg finasteride 5 mg cutting metoject 20 mg nebenwirkungen diclofenac losartan hctz 100 12 5 generic buy clomid uk without prescription diltiazem hcl er 180 mg msds misoprostol sale in nigeria queens albuterol inhaler prices walmart american lithium mines usa is there penicillin in ciprodex branduri celebrex imbracaminte online arava 10 mg tablets information leaflet writing dapoxetine baownbeuv online linezolid indian pharmacopoeia yearly cost of lipitor 80 mg prozac weight loss cephalexin 500 mg pill identifier cephalexin 250 mg. tablets cialis sell in mexico toronto canada buy cialis crazy meds forum zoloft reviews what is the cost of nexium otc bactroban pomada generico 0.1 mg synthroid valeriaanextract 45 mg mirtazapine propranolol teva lp 160 mg compeed cold sore ingredients in aleve diflucan price uk rare bupropion baownbeuv price tinidazole nombre generico de benadryl fludrocortisone supine hypertension in pregnancy propecia blind date died in spanish is benadryl safe to take in early pregnancy how long does 300 mg of neurontin last buyng viagra in sydney buy viagra no prescrition brand leader of ciprofloxacin in pakistan shoppers drug mart viagra price ca dramamine ukulele chords reality cetirizine for dogs atenolol 50 mg accion terapeutica clonidine transdermal system 0 3 mgday wat is diclofenac eg retard 75 mg how to buy cialis in the uk lamictal tabletas 100 mg warfarin aspirin 81 mg mestinon ivz online ratiopharm schmerztabletten 300 mg seroquel gabapentin drug price lithium air battery cost fosteum generic lexapro cost zyvox medication generic abilify 2mg rosuvastatin 10 mg cmax reviews buy amoxil online au viagra 50 mg kullan?m ?ekli diclofenac sandoz ec tablets 50 mg demerol buy clomid 150 mg online cheap avodart can wellbutrin xl be cut in half s adalat papers in plos one university college london cinarizina 25 mg posologia bactrim best time take tadalafil carvedilol 3.125mg reviews generic benadryl spray octane generico de crestor jounals peer premarin reviewed ramipril price uk samsung cetirizine 10 mg goutte 1000 mg metformin er synthroid for cheap piracetam 800 mg obat apa sering viagra online cluj buyinh viagra in amsterdam flonase review benadryl liquid for itching cardura 4 mg 20 tablet case 300 mg trileptal sintomas despues de haber usado misoprostol dexamethasone 0 5 mg untuk cinta doxepin liquid aricept sleep disorders losartan potassium 50 mg used for exelon patch prix kamagra beograd online tetracycline 250 mg capsules cafe augmentin dose in renal drysol inactive ingredients in prilosec putting viagra in someones drink prank amoxicillin dosing in pediatrics how to purchase arimidex singulair safe alcohol sertraline reviews fepanil 500 mg amoxicillin dosage zyprexa 5 mg high dose lamisil nail reviews fexofenadine 180 mg tablets ingredients in red order danazol online what is the price of ciprofloxacin 500mg in nigeria hydroxyzine 25 mg for nausea best time of day to take zoloft 50 mg sulfasalazine 500 mg pret prevacid 30 mg what is it for progesterone levels in early pregnancy fluctuate prednisolone 20 mg tabletten medicatie costo cytotec venezuela flag levonorgestrel and ethinyl estradiol tablets reviews buspirone patient uk leaflets purchase valacyclovir howdotofound irbesartan generic manufacturers of oxycodone doctors for low dose naltrexone australia cheap levothroid narcan drip clonidine overdose in toddlers albuterol for nebulizer cost bactrim 200 40 mg posologie paracetamol clomid howdotofound australia buy zovirax ointment online australia why phenytoin is not used in absence seizures safe alternative naproxen viagra online australia delivery gifts cialis sales cape town atarax 50 mg fiyat generic caverta india tapering off 100 mg zoloft viagraorder by phone n. c. crestor 10 mg 90 day supply mirza ghasemi ingredients in benadryl aldactone nome generico riverdale buspirone hcl 15 mg espanol piroxicam 20 mg adalah obat keputihan claritin pull from market suicide 22 protons 23 neutrons in lithium nexium 40 mg mecanismo accion lamisil generic how long metformin pharmacology review
Granite Island Group Banner

Non Linear Junction Detector Review and Tutorial

Back in the early 70's a method was developed to detect eavesdropping devices though the analysis of harmonic emissions caused by an illuminating signal when it is reflected off of a target. A few years later this method was used by the Superscout NLJD system (which was the first commercially available and patented NLJD).

Semiconductors contain multiple layers of silicon, a P-Type and an N-Type, the point where they meet is called a Non Linear Junction. This junction also appears in nature when dissimilar metals come in contact with one another (such as that used in the old crystal radio set). Also, the rust on a screw, the springs in a car, or the support structure in any piece of furniture may also contain non linear junctions (resulting from corrosion).

A Non Linear Junction Detector finds potential eavesdropping devices by flooding a suspect area or target with a spectrally pure microwave RF signal (usually around 888 or 915 MHz). Various frequencies are then monitored for a reflected harmonic signal.

The instrument typically has an antenna and a control unit. The antenna is mounted on an extendable pole, and really nothing more than a microwave waveguide which both emit and collects the signals (with a duplexer). The control unit is usually a multiple channel, highly sensitive radio receiver tuned to specific second, and third harmonic frequencies. While it is possible to measure the 4th, 5th, 6th, and other harmonics those above the third are only of limited TSCM value.



ORION NJE-4000 Non Linear Junction Detector

TSCM technicians are often portrayed in movies and marketing materials as someone slowly sweeping a wall with a complex device on a boom, carrying a control box over the shoulder, and a set of headphones over the ears (much like a metal detector). This portrayal actually shows the usage of a NLJD in action, and it has long since been accepted by the public as "how the job should look like."

A Non Linear Junction Detector may be used to identify:

A Non Linear Junction Detector is nothing more than an instrument which detects harmonic anomalies, nothing more. Any positive indication must be verified with a metal detector, X-Ray examination, thermal viewer, and a physical inspection to confirm the actual presence or absence of an eavesdropping device. While the NLJD is not a "magic wand" it is much less destructive then a sledgehammer and a number 14 screen.


How to Properly Use a Non Linear Junction Detector

Before using a NLJD the area must first be subjected to a comprehensive "Non-Alerting" TSCM inspection. This must include a "Non-Alerting" check for any type of free space electromagnetic signals including any signals or voltages present on all conductor combinations (including telephone, AC, lighting, HVAC, IDS, and so on). The area must also be checked for thermal and IR anomalies before the usage of the NLJD (which marks the beginning of the "Alerting" stage of the TSCM service).

If you only have limited time in which to perform the TSCM Inspection then the time is best spent on other elements of the sweep such as the RF survey (and you should leave your NLJD out of the equation). However, when you have the luxury of time and your schedule permits it usage; the NLJD becomes an invaluable tool just like the portable X-Ray or thermal imager (but it is very time-consuming to use).

Proper operation involves slowly brushing or sweeping the antenna over every surface in the suspect area. The procedure is very slow and time consuming, typically involving 2-5 minutes per square yard of surface area. A small 15 * 15 foot office will typically require four hours to sweep with such an instrument. The TSCM specialist literally "paints" every surface in the area, including walls, floors, ceilings, furniture, and fixtures. If a circular polarized antenna is used the time require to sweep can be reduced by about 30%.

The area to be inspected will first be swept using a "quiet" mode of operation where the instrument is used to listen only and to observe the quieting effect which RF fields tend to create. During this period the audio output of the NLJD may be monitored with headphones to detect the sync "buzz" created by video transmitters, or the emissions from the bias oscillator in some tape records (if you get lucky).

The illuminating signal will then be activated and the NLJD used to scan the walls and surfaces from a distance of at least 6-8 feet outside of the area to be inspected. The purpose of this scan is to isolate and evaluate items creating false positives. Once these item are "cleared" they should be isolated from the area being inspected (to avoid further interference).

Once the area has been sterilized of all major "harmonic reflectors" the distance between the NLJD is reduced to 2-3 feet and repeated to further isolate and evaluate potential "hits".

Finally the distance is reduced to between two feet and actual contact with the item or area being inspected. The lowest possible signal levels are used first for the initial "contact sweeps" and the entire area checked again. The power is then increased slightly (no more the 25%) and the entire area re-swept. The power is again increased and the entire sequence repeated until full power is reached. If possible the power should be increased in as small a level as possible (10% is ideal, but 25% is practical) with multiple overlapping sweeps of the area using multiple directions.

The flat surfaces (such as walls) in the area should be swept at a rate of 3 seconds per square foot or less. Non flat surface (such as furniture) will of course be swept at a much slower rate. A "perfectly clean room" will take at least 30 minutes to check with a NLJD, with a typical small office (less then 200 square foot) taking 2-3 hours, and a medium sized office taking at least 3-4 hours. A larger executive office may easily take 6-8 hours or more often involve several days just for the NLJD inspection. (On humorous note, the TSCM specialist will actually look like he is practicing Tai Chi with a painters pole). Properly sweeping a room takes as long as applying three coats of paint to all of the walls in a room (it takes time... lots of time, and is tedious).

Advanced NLJD Usage Methods

Since the use of a NLJD should be considered "highly alerting" the TSCM'er will be able to "thump and bump" possible metallic or corrosive targets to isolate them as false targets. Light switches, fluorescent lights, modern electronics, nails, paper clips, steel screw studs, furniture springs, and so on create the most false targets and will create a noisy and unpredictable response in the reflected signals.

Applying a small amount of physical vibration to the suspect area will disturb the crystalline structure of the corrosive or dissimilar junction and will usually cause a detectable shift in the NLJD reading. This physical vibration may be created by several commercial products including rubber mallets, orbital vibrators, low frequency ultrasonic vibrators, palm massagers, and so on. A false or corrosive hit will create a noisy signal which may be heard in the earphone, but a real threat may also cause such a crackle.

Each anomaly is then carefully documented and evaluated to determine exactly what caused the "hit" and a record of these should be maintained for future study.

Even when properly used Non Linear Junction Detectors are prone to false alarms, and may cause many hours to be expended only to find a paper clip which had been dropped into a potted plant, or two staples inside a book. On the other hand the NLJD may to used by the TSCM practitioner to develop a "sixth sense" about a area being inspected, and when combined with a portable X-ray, thermal imaging system, and borescope the instrument becomes invaluable for finding professionally installed eavesdropping devices.

Illuminating Signals and Harmonics

Transistors, diodes, integrated circuits, and other dissimilar or metallic junctions will usually cause a signal to be emitted at the second or third harmonic of the fundamental flooding frequency.

Fundamental or Illuminating Signal - Conductive or Metallic Surface
This is the flooding frequency, typically 888 Mhz or 915 MHz. Power levels range from 15 mW to 7.5 Watts, 3 W typical for government, below 1 W ERP for commercial. A reflection of this frequency may be monitored to allow the calibration of the instrument or to control output power levels.

Linear Response
A linear response will be caused when a NLJD is passed over a non metallic, non ferrous, or organic item. This material includes, potted plants, wood, paper, rubber, plastic, wool, fabric, or other item. Instead of reflecting the fundamental frequency, or generating a harmonic the signal is instead absorbed by the material. Most objects will respond in a linear fashion.

Fundamental Signal, 3rd, 5th, and other Odd Harmonic Reflections
(Conductive or Metallic Surfaces)

This harmonic will be reflected by any conductive or metallic surface within the area being inspected. Normally this harmonic is only useful for locating nails, screws, studs, conduit, and other normal structural components. This will include any metal to metal junctions of the same type of material such as electrical conduit, HVAC duct work, and metallic studs. This is considered a negative response and may be considered a non-linear symmetrical response.

2nd, 4th, 6th, and other Even Harmonic Reflections
(Dissimilar Metallic Junction and Non Linear Junctions)

Any type of metallic junction between multiple items of metal will cause a second harmonic to be generated. This signal may be created by solid state devices, diodes, transistors, or integrated circuits. However, this signal may also be caused by the presence of paper clips, rusty nails, sheetrock screws, steel studs, re-bar, upholstery springs, or any loosely touching metallic parts. This is considered a positive response, and will require further inspection involving a portable X-ray instrument, thermal imaging, borescopes, and other physical equipment. This may also be considered a non-linear assymetrical response. A noisy assymetrical response indicates the possibility of a corrosive target as opposed to a bugging device.

Power Level Issues

Non Linear Junction Detectors are available in a variety of power outputs ranging from the "civilian" version with an output below 25 mW, to the restricted Government version with a power output over 2 watts ERP. The Soviet and Chinese government actually use NLJD instruments which generate hundreds of watts of power, but often cost the TSCM specialist their vision (and other soft tissue damage) due to high levels of non-ionizing radiation. On an added note a NLJD should not be directed to any human or other living creature due to the potential of serious bodily harm. You can actually knock out a cardiac patients pacemaker from a distance with one, or cause serious soft tissue damage such as cornea injury, loss of hearing, kidney failure, and so on.

As the power output increases the greater the range of the unit, and the penetration into solid materials. However, as the power level increases, the sensitivity of the unit will decrease.

Normally a 2 Watt NLJD will detect an eavesdropping device through several inches of concrete, inside a wall, or buried deep inside a couch. The lower power units (50-100 mW) on the other hand will only detect eavesdropping devices inside a book, or devices only an inch or so away from the antenna (such as behind a few layers of sheetrock).

Non Linear Junction Detector transmit power is relatively meaningless. The sensitivity and bandwidth of the receiver is a far more important issue. Cheap units use high power to overcome poor receiver sensitivity and poor noise figures. In general the better units (more effective) are the lower powered ones.

Much like an X-ray the power level must be variable based on the density of the object being inspected. Of course the more power you generate the more "alerting" your activities become, and the higher the risk of personal injury (just like taking an X-Ray).

Generally a 1.5 Watt ERP unit with a variable output (adjustable down to around 5 mW ERP) works well, but if you use Digital Signal Processing or DSP in the unit to increase sensitivity the power levels can be drop to well below a Watt.

Frequency Issues

The 888 MHz products should be avoided as they tend to interfere with cellular telephone systems within the United States. On the other hand most professional eavesdroppers will monitor all popular NLJD channels to detect a TSCM sweep. For this reason it is advisable to utilize a non standard frequency, and to keep the power output as low as possible.

When a microwave sweep generator is synchronized and offset to a digital spectrum analyser the results are far superior to that of any NLJD (but much more expensive). For this reason NLJD's rapidly lost favor during the late 1980's, and have since been replaced with microwave sweep generators (if you don't mind dragging around an extra 60+ pounds of equipment). The technique of using a sweep generator as a NLJD signal is know a "Chirping".

A tunable NLJD works very well, but only after the spectrum has been checked with a spectrum analyzer. Also, the NLJD illumination signal may be pulsed to determine distance to the suspect junction and to reduce the power required (available in some NLJD systems). The pulse may also be created to appear like a legitimate communications signal (such as a POCSAG or CDPD data burst on an appropriate channel) to enhance operational security. Additionally, a pulsed signal may be coupled with a computer controlled receiver to radically increase the ability to detect potential threats.


NLJD Vulnerabilities and Weaknesses

Many modern eavesdropping devices utilize shielding and isolation circuits to hide the device from Non Linear Junction Detectors. Also, devices may contain special alarm circuits which will shutdown the device should a flooding frequency be detected or in some cases may even cause the device to self destruct with a small charge.

Perhaps the most valuable usage of a NLJD is the examination of organic, or quasi-organic objects such as potted plants, wooden desks, tables, books, and other things made of wood, fabric, composites, and non-metallic objects. The NLJD will also be valuable when examining wood paneling, wooden bookcases, paper, ceiling tiles, persian rugs, and so on. While a NLJD may be used with limited success on or near metallic surfaces such usage should be avoided as virtually every metallic junction will cause a false alert.

All weaknesses and misconceptions aside; the NLJD does have a place in every TSCM equipment inventory. When properly used during a sweep it will find eavesdropping devices that other instruments will miss. However; always remember that a NLJD is only one part of a complete set of TSCM equipment, and that it is only as good as the operator.


Popular Industry Models


| Spectrum Analyzers | Vector Signal Analysers | Demodulation | Time Domain Reflectometers |
| Antenna | Oscilloscopes | Multimeters | Craft Instruments | TSCM Specific Instruments |
| Non Linear Junction Detectors | Acoustic | Physical Search | Photographic and Imaging |
| Auxillary | Ancillary | Video | Vehicles |


Advanced TSCM Signals Detection and Analysis
TSCM - Sweeping the Spectrum for Eavesdropping Devices

Advanced TSCM Signals Detection and Analysis
TSCM - Sweeping the Spectrum for Eavesdropping Devices

Any comments or questions regarding this specific page?

Please feel free to sign our Guest Book

Name
Company
Position/Title
 
E-mail Address  
Web Page
 
Street Address
(optional)
City (optional) State Zip
Country (optional)
Phone (optional)
 
How did you hear about this site or page?
Do you need to have a bug sweep or other TSCM service performed?
Do you need any TSCM equipment?
 
Comments



| Home | What is TSCM | Types of Bugs | Warning Signs You're Bugged |
| How To Behave if Bugged | TSCM Threat Levels | How To Engage a TSCM Firm |
| Qualifications | TSCM Protocol | Bug Frequencies | Phone Taps and Bugging |
| Signal Analysis | TDR Analysis | TDR Tutorial | Wiretapping | Training | Tools |
| Equipment | OSC-5000 | Kaiser | Riser Bond | Avcom | Search Rcvrs |
| Outside Links | Recommended TSCM Books | TSCM Reference Library |
| Recommended U.S. TSCM Firms | TSCM-L Mailing List |


-

    To be contacted for a confidential consultation
    please E-mail: jmatk@tscm.com

    or send a letter via US Mail to:
    James M. Atkinson
    Granite Island Group
    127 Eastern Avenue #291
    Gloucester, MA 01931-8008

    or call:
    Telephone: (978) 546-3803 / Fax: (978) 546-9467

    URL: http://www.tscm.com/

Copyright ©2002, Granite Island Group