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5.2 Troubleshooting If a system malfunction occurs, system troubleshooting techniques may identify the transmission line as one cause of the system malfunction. If this occurs, troubleshooting of the transmission line is directed toward determining the location of the defective segment(s) along the transmission line length. The following troubleshooting information describes possible operational performance malfunctions, causes, and corrective actions. If transmission line repair becomes necessary, refer to the repair/corrective maintenance section of this manual for proper procedures. 5.2.1 No Pressurization Loss of pressurization may be due to an outer conductor rupture or severe leaks at the outer conductor flange joints. Inspect the cable and flange joints for sources of leakage. If an outer conductor rupture is severe, a TDR test (see Section 6.2) will show an impedance deviation that can be used to locate the rupture. Loss of pressurization may also be due to the pressurization system. Check the system for a possible malfunction. 5.2.2 Excess Humidity or ON-Time Operation of Pressurization System Excessive humidity or a long operating time for the pressurization system may be due to small cracks in the outer conductor, or flange joint leaks. Inspect the cable and flange joints. Tighten any loose bolts to a torque of 38 to 40 ft-lb. Also inspect the purge valve since this condition may be caused by a poor or leaky seal, and again check for a possible malfunction in the pressurization system. 5.2.3 High VSWR Physical damage to the transmission line will cause high VSWR. Inspect the line for damage. A TDR test of the cable (see Section 6.2) can be used to locate an impedance deviation along the cable that is causing the high VSWR. 5.3 Repair/Corrective Maintenance Repair of the 10-inch (254 mm) semiflexible transmission line is performed by replacement of the damaged 38-ft (11.6 m) cable section(s). Defective sections are replaced by new standard sections which are installed using the same techniques as the initial installation, except for the final section which is replaced by a custom repair section. The custom transmission line repair section is comprised of two half-length cable segments, each having an EIA-type captive connector on one end. The other end is a standard SCL950 interface. The installation procedures for the repair section are given in Section. 5.5. NOTE: Read the CAUTION statements in the introductory paragraph to Section 3 (Installation) prior to installation of a repair section. (These refer to handling the cable and cleanliness.) |
CAUTION: After repairing the transmission line, ensure
that it conforms to the specified tests in
Section 6 Verification of Performance,
before putting the broadcast system into operation. 5.4 Tools and Equipment for Installing Repair Section 5.4.1 General Equipment This equipment is recommended for general installation needs during repair: Assorted hand tools 5.4.2 Special Tools
5.5 Installation of Repair Section The repair section is intended to replace one 38-ft (11.6 m) standard section of SCL950 cable as described in Section 5.3. If damage occurs to only one transmission line section, then this section is removed and replaced by a repair section. If damage occurs to several adjacent transmission line sections, then new standard sections are installed in addition to a final repair section. As detailed in Section 3, installation of standard sections occurs at the transmitter end of the existing transmission line. Thus, the repair section replaces the damaged section that is closest to the antenna end of the line. |
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