Free NWSA Antenna and Line Installation Questions and Answers 1 — Questions and Answers
Question 1: When performing a sweep test (or VSWR test) on a newly installed coaxial cable run, what is the primary purpose of this test?
- To measure the cable's resistance to weather and UV exposure.
- To verify the cable and its connectors meet performance specifications across a range of frequencies. (Correct answer)
- To determine the maximum power handling capacity of the transmission line.
- To locate sources of Passive Intermodulation (PIM) caused by loose connections.
Correct answer: To verify the cable and its connectors meet performance specifications across a range of frequencies.
A sweep test, also known as a VSWR (Voltage Standing Wave Ratio) test, is performed to ensure the transmission line system (cable and connectors) meets the manufacturer's performance specifications. It checks for issues like high signal loss or reflections caused by damage (dents, tight bends) or improper connector installation.
Question 2: A technician is installing antenna mounting hardware that specifies a torque value of 60 ft-lbs for the 5/8" bolts. The technician only has a torque wrench that measures in inch-pounds. What value should the technician set the wrench to?
- 600 in-lbs
- 120 in-lbs
- 720 in-lbs (Correct answer)
- 660 in-lbs
Correct answer: 720 in-lbs
To convert foot-pounds (ft-lbs) to inch-pounds (in-lbs), you multiply by 12, because there are 12 inches in a foot. Therefore, 60 ft-lbs multiplied by 12 equals 720 in-lbs.
Question 3: Which of the following best describes Passive Intermodulation (PIM) in an antenna and line system?
- A measure of the signal reflected back towards the transmitter due to an impedance mismatch.
- Unwanted interference signals generated when two or more carrier frequencies mix at a non-linear junction, such as a corroded or loose connector. (Correct answer)
- The loss of signal strength (attenuation) as it travels along the length of a coaxial cable.
- External radio frequency interference from nearby broadcast towers or other cell sites.
Correct answer: Unwanted interference signals generated when two or more carrier frequencies mix at a non-linear junction, such as a corroded or loose connector.
PIM is a form of signal distortion that occurs when two or more high-power signals mix in a device with non-linear characteristics. Common causes include poor connections, contamination, or damaged components in the RF path, which can create interference and degrade system performance.
Question 4: During the installation of a new transmission line on a tower, a technician must use a hoisting grip to lift the cable. Where should the hoisting grip be attached to the cable for a vertical lift?
- At the midpoint of the cable to balance the load.
- Near the connector at the top end of the cable. (Correct answer)
- Loosely around the cable jacket to allow for movement.
- Several feet below the connector to avoid stress on the connection point.
Correct answer: Near the connector at the top end of the cable.
Hoisting grips, often called 'Kellems grips' or 'pulling grips', are designed to securely attach to the cable jacket just below the connector. This allows the lifting force to be applied to the grip and cable, preventing stress and potential damage to the sensitive, load-bearing connector and its attachment point on the antenna or radio.
Question 5: A tower crew is tasked with weatherproofing a 4.3-10 coaxial connector on an antenna jumper. What is the standard, multi-layer method for ensuring a long-lasting, watertight seal?
- A single, thick layer of electrical tape wrapped tightly around the connector.
- Injecting silicone sealant directly into the connector threads before tightening.
- Applying a layer of vinyl tape, followed by a layer of butyl mastic tape, and finished with an outer layer of vinyl tape. (Correct answer)
- Using a heat-shrink tube without any underlying tape layers.
Correct answer: Applying a layer of vinyl tape, followed by a layer of butyl mastic tape, and finished with an outer layer of vinyl tape.
The industry-standard method for weatherproofing involves a three-layer approach. An initial 'courtesy' wrap of vinyl electrical tape protects the connector, followed by a layer of butyl mastic rubber tape that forms the primary waterproof seal. A final outer wrap of vinyl tape protects the butyl from UV rays and mechanical damage.
Question 6: While reviewing a closeout package for a recent antenna installation, you notice the PIM test passed, but the Return Loss (VSWR) test failed. What does this combination of results most likely indicate?
- The test equipment was not calibrated correctly.
- There is a loose or corroded connector causing non-linearities in the system.
- There is an impedance mismatch, possibly due to a damaged cable or faulty antenna, but the connections are clean and tight. (Correct answer)
- The antenna is installed at the wrong azimuth.
Correct answer: There is an impedance mismatch, possibly due to a damaged cable or faulty antenna, but the connections are clean and tight.
PIM testing and Return Loss (VSWR) testing measure two different aspects of a system's health. PIM tests for system linearity, often failing due to poor or corroded connections. Return Loss tests for impedance mismatches, which can be caused by physical damage to the cable, a faulty component like an antenna, or an incorrect component type. It is possible to have a clean, tight connection (passing PIM) on a damaged cable (failing Return Loss).
Free NWSA Antenna and Line Installation Questions and Answers 1
When performing a sweep test (or VSWR test) on a newly installed coaxial cable run, what is the primary purpose of this test?