TDR Tutorial and Riser Bond TDR Product Review
CATV
APPLICATION #1 The case of the missing signal.
Sometimes, a perfectly good cable goes bad for no apparent reason. Take the case of the disappearing church services. A local church broadcasts Sunday services on cable. One Sunday, they called the cable technician to report their signal was not getting onto the cable. After verifying the problem was not within the transmitting equipment, the cable was the next item to check.
A 2,100 foot cable ties the church into the cable system. Checking from the church out, the TDR indicated an open at 2,000 feet. Checking from the other end back toward the church, the TDR indicated an open at 108 feet.
With the aid of a TDR and measuring wheel, the problem was quickly found; a new school crossing sign placed along the road the week before had been driven right through the cable, cutting it in half. The time to repair was less than 30 minutes.
APPLICATION #2 The case of the corroded splice.
Within many systems, there are a lot of cable splices in the ground. Many are old and their locations are unknown. With every splice, it is just a matter of time before they can go bad.
Customers started calling in one afternoon to report that their TV was snowy. The technician checked and found a 300 foot length of distribution cable had 24 dB excessive loss. With the aid of a TDR, a corroded underground splice was easily located and repaired.
APPLICATION #3 The case of the unidentified cables.
The construction crew was burying new cable. Each pedestal had at least two cables in it, with some having as many as five. The crew placed the pedestal, buried the cable, and stubbed it off in the pedestal. They were not consistent or accurate about identifying and marking the various cables . With the aid of a TDR and the plant map which showed cable lengths between each pedestal, the cable technician was able to identify the various cables by their length. The time it took to activate the cable was decreased significantly.
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