Wavetek 147 Spécifications télécharger pdf (Page 121)

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Reverse Path Troubleshooting: Problems in Advanced Services

Fig. 5-2 Customers Affected by a Return Path Ingress

Source

To see how this affects noise floors, think about how much of the network

can inject noise that affects a given customer. For forward path signals,

the only potential problem areas are the direct path from the customer’s

home to the headend. For reverse path signals, problems can come from

anywhere in the area served by one headend receiver.

• Many Diverse Ingress Sources: There are an increasing and varied

number of RF energy transmitters in the reverse path bands. CB radio,

short-wave, ham, paging, and land mobile all use the same frequencies

as a cable reverse path. Rather than a few transmitters (even at high

power) at known locations (where better care can be taken with

shielding), there are lots of transmitters that can be right next to the

network that are not controlled.

• Random Noise: Noise can be generated by non-transmitters too.

Electric motor switching, welding, computers, even power supply

switching can have energy in the reverse path band.

• Physical Plant Problems: Small cracks in powered coax or dissimilar

metal "diodes" can create CPD (common path distortion) or noise.

Fiber

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