augmentin 375 dosage for enteric fever pcos metformin mfg mylan olanzapine 2.5 mg tablet ciprofloxacin 500 price uae zithromax 500mg dosage std losartan hydrochlorothiazide philippines prozac 10 mg to 5 mg top best telmisartan brands in india can you take propranolol with cymbalta can biotech ciprofloxacin 250 be used to treat sti stopping wellbutrin xl 300mg cold turkey dostinex 2 tabletki purchase propecia finasteride benefits of lexapro in sleep lchf diet and duromine taper prednisone 40mg over 14 days bloqueadores adrenergicos prazosin mekanisme kerja januvia dengan metformin zyvox and mystenia gravis interaction amlodipine walmart ghorse trazodone xeloda 500 mg effetti collaterali periactin 1 year old tabletas benicar para sirve coumadin 5 mg tablet fiyat?± buy viagra online legitimate pharmacy can clomid be combined with cipro does medicare cover enteric coated metformin nolvadex 10 mg tabletas clomid 150mg. ovulated no pregnancy no period valacyclovir hcl 1000mg dosing diverticulitis flagyl dosage sertraline and pineapple generic lexapro headaches cipro or amoxyl for infection of tooth escitalopram actavis 10mg order xenical online pharmacy zyvox synthesis upper age limit for viagra amoxicillin 100mg what is the purpose of baclofen will 2 buspirone tabs get you high galcipro 500 perdida de memoria por finasteride generic conjugated estrogens cream amoxicillin 500mg trexil for cough propranolol er migraine reviews how long does diflucan work in your body manfaat obat oral meloxicam can i use lamisil once on dog voltaren gel 60 g cena price of metronidazole in india risk of use clopidogrel ppi does amoxicillin cause hunger tapering of diltiazem in use for tachycardia can you take amoxicillin with tums dangers of ciprofloxacin and amoxicillin prednisone 20 mg side effects in dogs para que es ondansetron odt 4 mg zestril 10 mg para que sirve fosamax price in india order viagra online no rx prescription metronidazole nystatin price sonusitis ude of levofaxalin azithromycin stop propecia for laser 5 mg lexapro started migraines avodart 0.5 mg taking 4 azithromycin at one time acidic reflux and olanzapine withdrawal pagin forte og atarax mayo clinic use of cipro macrobid doxycycline injection marketed in india topamax dose for tmj bupropion make you high the first time brand levitra paypal amoxicillin 500mg untuk mata where can i buy misoprostol and mifepristone ciprofloxacin cats can tamiflu be taken with lisinopril combine propecia with flomax buy montelukast 10 mg online teva and montelukast gluten free plavix generic 75 phenergan 25 interact with augmentin duo forte cytotec medicine. supplier. singapore phone number augmentin 200 mg kullan?±m?± taking ondansetron while pregnant esomeprazole manufacturing process indian patents clonidine 5 year old can a 2 year old take singulair and benadryl 80mg recreational value of strattera famciclovir antiviral activity buy cheap bactrim online propranolol 5 mg tablet lisinopril without prescription venta de pastillas cytotec miami harga verapamil lisinopril hctz lethal dose strattera 3250 doxycycline capsules for sjogren amoxicillin side effects in men augmentin and flagyl is prescribed for std buy vardenafil hcl 20mg tab can augmentin and erythromycin delay menstruation dosage of cialis per body weight can u get high off robaxin and neurontin what is the street value of naproxen 500mg olanzapine teva versus olanzapine activas dirty feeling elavil how much does a cialis prescription cost cipro 500 od in acute cholecystitis generic zithromax 1 gram usa can you masturbate while taking diflucan hydrochlorothiazide rash benadryl bactrim forte for pregnancy of 10 weeks. im have zoloft withdrawal symptoms canada pharmacy viagra no prescription stopping benicar suddenly cause headache gabapentin 600 istruciones en espanol linezolid drug dosage in renal failure patients teva telmisartan hct 80 12.5mg precio amoxil 250 mg capsule infection urinaire enfant augmentin 375 dose apo amitriptyline 25mg side effects imipramine for duloxetine withdrawal etodolac 400 mg tab teva usa nizoral cream otc paroxetine 10 mg azithromycin from india will i notice going from 100mg of zoloft to 150 buy amoxicillin potassium clavulanate how many tablet of amoxil is a 19year old to take viagra for cheap online generic medicine for singulair cialis argentina carvedilol 12.5 mg 7295 does red bull has viagra in it how long does it take for bactrim to work on staph singulair price in india augmentin tablet 250 rupee can ramipril and amlodipine can be use with kamagra diflucan fluconazole over the counter 7years old boy amoxil capsul 500mg dosage can inderal treat premarture enjaculation ordering viagra online legal methergin despues de usar cytotec anafranil 25 gr lovaquin or cipro uses seroquel xr 100mg how does it looks like prochlorperazine and amoxicillin topamax prior to surgery levaquin 500 mg tratamiento does elavil get you high plavix vs aspirin after stent propecia without doctor medicinal tablet premarin 625 information septran pharmacodynamics ondansetron hyperemesis uk hyoscine hydrobromide 300 micrograms purchase flagyl cream can amoxicillin be taken 1g b.d for typhoid fever xenical online what is azithromycin used for generic cialis india online can u take austell ciproflaxin for throat infections trazodone 300mg side effects how do i know cytotec worked can you take lipitor on an empty stomach viagra generic in mexico trazodone hydrochloride street price viagra online bestellen metronidazole suspension mexican viagra online zyprexa hair loss conversion iv lasix to po generic bupropion sr manufacturers can you drink while on antibiotics for strep lipitor 40 mg dosage white amoxicillin liquid and pink can i buy metronidazole gel over the counter shelf life of premarin cream once opened 4 weeks pregnant shold i take pot city and flagyls priligy availability in italy powder antibiotics for cats wholeseller amoxicillin side effects if taken with antihistamines how much does doxycycline cost in nigeria buy azithromycin powder packets doxazosin 1 mg can you take lisinopril every other day cost of sertraline in new jersey amlodipine 10mg tab cam amlodipine e impotencia buy glucophage xr online no prescription escitalopram insomnia fluconazole buy online uk bystolic to coreg conversion how much does a pill of colchicine cost on the street how much mgs is 4 zithromax dog with asthma use albuterol 4mg inderal tablete upotreba can i take azithromycin tablets with omezole cheapest place to get amoxicillin liquid blairsville ga can you take evening primrose oil with citalopram phenergan amp dose in pedi clomiphene citrate online australia amoxicillin duo 1000 uses floxar sr ciprofloxacin levofloxacin tabletspcshelf life sildenafil citrate tablets lp fk 100 would overdose seroquel avanza alcohol suicide doxycycline severe headache glimepiride 2mg can amoxicillin cause tiredness in infants citalopram sandoz 20mg at cosco seroquel 25 mg teilbar akara viagra cat mirtazapine spraying nitroglycerin controlled release tablet mixing cetirizine with metronidazole kasiat tetracycline buy neurontin online no prescription levitra geciktirirmi can we gibe digoxin for myocaritis pil misoprostol di farmasi kl fluconazole nail paint is amoxil milk free levofloxacin for tooth infection is azrithromycin antibiotics found in nigeria naprosyn 250 cipro cure tablets buy zofran uk levitra cheap amoxicillin liquid peanuts ondansetron hcl 4 mg iv buy zyprexa online cheap levofloxacin floxel 750 mg how much is azithromycin in nigeria can i take fluconazole twice levitra expiration date taking viagra and extenze at same time can doxycycline cause pluerisy cipro 400 mg iv generic viagra 100mg exporters can you take viagra with afib metoprolol buy uk furosemide diuspec suitable for pregnant how to take amoxicillin 1000 for chlamydia flomax para que sirve maxalt rpd mayo clinic list of orlistat med in phils what is the dose for cipro for uti dexamethasone .75 for pain buy generic cymbalta canada prednisone taper doses before surgery buspar 60 mg a day how to make homemade albuterol can i import thyroxine tablets into australia generic avapro available lexapro lethal dose 60mg montelukast drug sales in bangladesh market analysis can ciprotab cure chlmydia is keflex in the tetracycline famiky generic anastrozole india periactin nz is tamoxifeno bad for a person with lagtose intolerance can you take cipro for an ear infection quetiapine fumarate and paxil inderal 10 azithromycin 93 7169 medroxyprogesterone 10 mg menstruation 2g amoxicillin how much do squirrel antibiotics cost erectzan in indian drug shop nizoral cream philippines price azithromycin price at cvs plavix tablets side effects before angiogram atarax 10mg cytotec price pfizer can flagyl and tetracycline terminate 7weeks pregnancy gabapentin sciatic nerve dog puedo tomar augmentin and piroxicam juntos how long will it take to flushing cialis of your system generic celebrex release date viagra for sale with paypal fexofenadine 120mg can i take two how long should you take clomid after a cycle hoe werkt valsartan 100g clomid cyproheptadine street name buy plavix manufacturer clopidogrel australian prescriber amoxil syrup without prescription como tomar cytotec para abortar paso a paso how to make a bactrim ds suspension for cats levitra 400 harga nizoral ketoconazole cream generic viagra buy lexapro price at walgreens what is the alternative to ciprofloxacin ear drops can i take 1800 mg neurontin for chronic back pain linezolid gonorrhea uti urinary tract infection lasix no prescription needed is doxycycline hyclate 100mg good for mrsa buy clomid women where can i buy propecia in ireland cyproheptadine appetite stimulant cancer how fast does zyprexa work lisinopril 2.5 no prescription antibiotics 30 eryc how long does it take to work amoxil 500 mg for toothache menses problem provera5mg ketoconazole shampoo ingredients flagyl online no prescription buy propecia over the counter bactrim shingles clomid pills online uk escitalopram ginecomastia what is cialis c80 estradiol derm 75 buy kamagra online india biotech ciprofloxacin tablets for sti cytotec 7 pastillas posso tomar o provera em 8 em horas how do you treat men with metronidazole gel baclofen cost orlistat farmacia popular manfaat tablet amoxicillin 500 mg forum generic cialis doxycycline and ambroxol for acne penicillin vk and doxycycline used together amoxicillin cost cvs is nexium making me sicker citalopram 70 mg side effects of gabapentin in dogs can i take advil and nexium together 60 mg prednisone daily augmentin 1000 duo side effects what other medication in mexico is like coreg meloxicam 30 mg dose how to take metformin pcos with less side effects order diltiazem cream what happens if you take two allegra d in 24 hours seroquel e cocaina salep acyclovir untuk cacar obat zoloft plavix with epidural catheter increasing lexapro to 10mg while pregnant ebay uk propecia how many capsules of cipro do i take forgonorrhea buy amitriptyline can i take buspar with oxycodone sildenafil with 30mg of dapoxetine dostinex 0 5mg cabergolina usar cytotec despues de cesarea erythromycin 250 mg can the be taking for gums generic drug for propranolol combine clomid and progesterone order lisinopril hctz online crack syraquil prozac cozaar 50mg dosage viagra in philippines can you take zoloft and reglan together depo provera 400 mg ml cytotec para compra en brecelona numero tefemono should i take premarin after 70 is buspirone illegal in the ncaa is valtrex or acyclovir stronger buspirone hd dapoxetine 60gm pills levaquin 500mg and sore neck can i take 400mg of fluconazole at one time doxycycline frequent urination alendronate bisphosphonate price generic kamagra viagra priligy available on nhs what is a fatal dose of metoprolol tartrate hoeveel kost wellbutrin how long for fluconazole to work is propranolol a street drug can the health department prescribe clomid what antidepressant can i take while taking maxalt ciprofloxacino 500 sirve para avortar side effects of taking clomid and metformin period 6 weeks apart on glucophage smallest dose of buspar taken with positive results phenergan for 3 month infants dose india how to get off clonidine hcl0.1mg nortriptyline hydrochloride 10 mg and insomnia can i take propranolol with fluoxetine minimum dose of bactrim ds for uti single forgot to take lexapro side effects buy accutane now tamsulosin hydrochloride nature levitra buy levitra online viagra cheap kamagra viagra does folic acid increase topamax topiramate for bipolar type1 be tab prednisone eczema dosage 6 months terbinafine nursing implications for olanzapine accutane 30 mg log metformin manufacturers can tamsulosin cause gout pamelor next step for migraines
Granite Island Group Banner

TDR Tutorial - Introduction to Time Domain Reflectometry

An Introduction to Time Domain Reflectometers

Time Domain Reflectometers have been around for many years and remain the fastest, most accurate way to pinpoint cabling problems.

Historically, the TDR has been reserved for only large companies and high level engineers. This was due to the complexity of operation and high cost of the instruments. The TDR has been greatly under utilized.

Riser-Bond Instruments recognized these shortcomings and developed the first "little TDR" in the early 1980s. The simplified digital TDR has now become a standard tool for the first level technician. Riser-Bond Instruments' complete product line has been permeated by the concept that test equipment should be simple, accurate, user-friendly, rugged, and high value for the cost.

Due to advances in today's technology, the operation and interpretation of a TDR have been greatly simplified. Because of its ability to identify cable problems, the TDR is now rapidly regaining popularity throughout communications industries.

If a cable is metal and it has at least two conductors, it can be tested by a TDR. TDRs will troubleshoot and measure all types of twisted pair and coaxial cables, both aerial and underground.

TDRs are used to locate and identify faults in all types of metallic paired cable. TDRs can locate major or minor cabling problems including; sheath faults, broken conductors, water damage, loose connectors, crimps, cuts, smashed cables, shorted conductors, system components, and a variety of other fault conditions. In addition, TDRs can be used to test reels of cable for shipping damage, cable shortages, cable usage, and inventory management.

The speed and accuracy of the time domain reflectometer makes it today's preferred method of cable fault location. Although today's instruments are more user friendly, a good understanding of the basic principles and applications of a TDR is essential to successful troubleshooting. Like all new equipment, getting to know the instrument and its operation makes the TDR a more valuable tool.

Principles of Operation

The TDR works on the same principle as radar. A pulse of energy is transmitted down a cable. When that pulse reaches the end of the cable, or a fault along the cable, part or all of the pulse energy is reflected back to the instrument.

The TDR measures the time it takes for the signal to travel down the cable, see the problem, and reflect back. The TDR then converts this time to distance and displays the information as a waveform and/or distance reading.


There are two ways a TDR can display the information it receives. The first and more traditional method is to display the actual waveform or "signature" of the cable. The display, which is either a CRT or an LCD, will display the outgoing (transmitted) pulse generated by the TDR and any reflections which are caused by impedance discontinuities along the length of the cable.

The second type of display is simply a numeric readout which supplies the distance indication in feet or meters to the first major reflection caused by an impedance change or discontinuity. Some instruments also display if the fault is an OPEN or SHORT indicating a HIGH IMPEDANCE change or a LOW IMPEDANCE change respectively.

Traditional Waveform TDRs supply more information than do the digital numeric versions. However, the simplified digital models are less expensive and easier to operate. Costing only a fraction of a traditional TDR, many simplified digital TDRs are just as accurate and can locate most major cable faults.


Any time two metallic conductors are placed close together, they form a cable impedance. A TDR looks for a change in impedance which can be caused by a variety of circumstances, including cable damage, water ingress, change in cable type, improper installation, and even manufacturing flaws.

The insulating material that keeps the conductors separated is called the cable dielectric. The impedance of the cable is determined by the spacing of the conductors from each other and the type of dielectric used.


If the conductors are manufactured with exact spacing and the dielectric is exactly constant, then the cable will be constant. If the conductors are randomly spaced or the dielectric changes along the cable, then the impedance will also vary along the cable.

A TDR sends electrical pulses down the cable and samples the reflected energy. Any impedance change will cause some energy to reflect back toward the TDR and will be displayed. How much the impedance changes determines the amplitude of the reflection.



Many TDRs have selectable pulse width settings. The larger the pulse width, the more energy is transmitted and therefore the further the signal will travel down the cable. Pulse widths may include 2 nsec, 10 nsec, 100 nsec, 1000 nsec, 2000 nsec, and 4000 nsec. A TDR may contain only one or all of the pulse width settings.

NOTE: Even when testing very long lengths of cable, always start the fault finding procedure in the shortest pulse width available, as the fault may be only a short distance away. If the fault is not located, switch to the next larger pulse width and retest. Keep switching to the next larger pulse until the fault is located.

Sometimes larger pulse widths are helpful even for locating faults that are relatively dose. If the fault is very small, the signal strength of a small pulse may not be enough to travel down the cable, " see" the fault, and travel back. The attenuation of the cable combined with the small reflection of the partial fault can make it difficult to detect. A larger pulse width would transmit more energy down the cable, making it easier to see the small fault.


The pulse generated by the TDR takes a certain amount of time and thus distance to launch. This distance is known as the blind spot. The length of the blind spot varies with the pulse width. The larger the pulse width, the larger the blind spot.

It is more difficult to locate a fault contained within the blind spot. If a fault is suspected within the first few feet of cable, it is advisable to add a length of cable between the TDR and the cable being tested. Any faults that may have been hidden in the blind spot can now easily be located. When adding a length of cable to eliminate the blind spot, remember the TDR is also reading the length of this jumper cable. The length of the jumper must be subtracted from the cable when measuring from the point of connection.

It is best if the jumper cable is the same impedance as the cable under test. The quality of the connection is an important factor regardless of the type of connection or jumper being used.


The TDR is an extremely accurate instrument. However, variables in the cable itself sometimes cause errors in distance measurements. One way to minimize error is to use the correct Velocity of Propagation (VOP) of the cable under test. The VOP is a specification of the cable indicating the speed at which a signal travels down the cable. Different cables have different VOPs. In order to assure the most accurate distance measurements, the cable VOP must be determined.

VOP Defined: The speed of light in a vacuum is 186,400 miles per second. This speed is represented by the number 1 (100%). All other signals are slower. A cable with a VOP of .85 would transmit a signal at 85% of the speed of light. A twisted pair cable, which typically has a lower VOP (such as .65), can transmit a signal at 65% of the speed of light.

The VOP number of a cable is determined by the dielectric material that separates the two conductors . In a coaxial cable, the foam separating the center conductor and the outer sheath is the material determining the VOP. In twisted pair, the VOP number is determined by the spacing between the plastic.

Knowing the VOP of a cable is the most important factor when using a TDR for fault finding. By entering the correct VOP, the instrument is calibrated to the particular cable. Typically, the VOP of the cable under test will be listed in the cable manufacturer's catalog or specification sheet. If not, simply measure a length of good cable (no faults) and change the TDR's VOP setting until the display shows the same distance reading as the measured length. The VOP of a cable can change with temperature and age. It can also vary from one manufacturing run to another. Even new cable can vary as much as +/- 3%.

One might think the variations in VOP would make it almost impossible to locate a fault accurately. Fortunately, there are ways to minimize the error in the VOP when testing a faulted cable, resulting in very accurate distance measurements. These techniques do not work when testing or measuring good (no fault) cable.

The most common technique used to reduce VOP error is to test the faulty cable from both ends. The procedure is as follows:

Determine the path of the cable. With a Measuring wheel or tape, measure the exact length of the cable being tested. Set the VOP according to the manufacturers specifications, test the cable from one end, and record the distance reading. Next, using the same VOP setting, test from the opposite end of the cable and record. If the sum of the readings is the exact length of the cable that was measured, the VOP is correct and the fault has been located.

If the sum of the two readings is more than the measured distance, reduce the VOP setting and re-test. If the sum of the two readings is less than the measured distance, increase the VOP setting. In this case, the operator must also consider the possibility of two faults.

The same result can be obtained mathematically. Take the actual cable length and divide by the sum of the two TDR readings obtained by the tests from each end . This gives the adjustment factor. Then multiply each of the TDR readings by the adjustment factor. This result will be the corrected length readings.

A partial listing of cable types and their Velocity of Propagation.


19 AWG Gel-Filled 68
22 AWG Gel-Filled 66
24 AWG Gel-Filled 62
26 AWG Gel-Filled 60
19 AWG AIR 72
22 AWG AIR 67
24 AWG AIR 66
26 AWG AIR 64
Polyethylene 66
Polypropylene 66
Teflon 69
PIC 67
Pulp 72

BeldenFoam 78S-82
Solid 66
Comm/Scope (F) 82
QR 88
Times Fiber RG-59 93
T4,6,10,TR+ 87
TX, TX10 89
Dynafoam 90
Trilogy (F) 83
CapScan FOAM S2
CC SS 88
CZ Labs FOAM 82
General Cable RG-59 82
MC2 93
Scientific AtlantaRG-59 81
Trunk 87
UTP 26 64
Thinnet 66-70
Ethernet 77
Token Ring 78
Arcnet 84
Twinaxial AIR 80
Twinaxial 71
Appletalk 68
Type 1 64
Type 2 66
Type 3 70
Type 4 72
Type 5 76
Type 6 78
Type 7 82
Type 8 84
Type 9 82
FHJI-50 1/4" 79
FSJI-50 1/4" 78
FSJ4-50B 1/2" 81
LDF2-50 3/8" 88
LDF4-50A 1/2" 80
LDF4-75 1/2" 88
LDF5-50A 7/8" 89
LDF7-50 1 5/8" 88
FT4-50 1/2" 85
FT5-50 7/8" 89
HJ4-50 1/2" 91
HJ5-50 7/8" 92
HJ5-75 7/8" 90
HJ7-50A 1 5/8" 92
HJS-50B 3" 93
HJ11-50 4" 92
HJ9-50 5" 93
FLC12-50J 1/2" 88
FLC78-50J 7/8" 88
FCC 38-50J 3/8" 81
FLC 12-50J 1/2" 88
FLC 78-50J 7/8" 88
FLC 158-50J 1 5/8" 88
920213 7/8" 99
920214 1 5/8" 99
HCC12-50J 1/2" 91
HCC7S-50J 7/8" 91
HCC15S-50J 1 5/8" 95
HCC300-50J 3" 96
HCC312-50J 3 1/2" 96
HF41/2CU24 4 1/2" 97

| TDR Principles of Operation | Usage Techniques | Waveform Analysis |
| General | CATV | Telephone | Broadcast | Cellular | 2-Way Radio | Power | LAN/WAN |
| Dual Twisted Pair and Coax TDR | Dual Twisted Pair TDR | Coax TDR | Basic Numeric TDR |

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

| 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 |


Copyright ©2002, Granite Island Group