Inspect and restore oxidized RF connections

This guide shows how to find and treat oxidation on radio frequency (RF) connections, the metal parts through which the signal passes between the radio, the cables and the antennas. In TECER’s Phase 1, the technical team found oxidation inside one of the base stations during the tests at UFPA/LASSE, which helped explain the reduced range of the links.

Oxidation is common in equipment installed outdoors, especially in hot and humid places. An oxidized connection reduces the strength of the signal even when the cables are in good condition.

What you need

• Tools to open the equipment, according to the manufacturer’s manual.
• Isopropyl alcohol and small swabs or brushes that do not leave lint.
• Electrical contact cleaner.
• Protection against new oxidation, such as dielectric grease or another protectant suitable for RF connectors.
• Self-amalgamating tape and electrical tape, to seal outdoor connections.
• A spectrum analyzer or the equipment’s own signal meter, to compare before and after.
• Replacement cables and connectors.

Steps

1. Measure before touching anything. Record the power or signal level of the link to have a reference. In Phase 1, the team measured the power before the repair to assess the impact of the oxidation.
2. Switch off and disconnect the equipment from the power supply.
3. Inspect each connection: cable connectors, antenna ports and, when the manufacturer allows the equipment to be opened, the internal connectors. Look for greenish, whitish or dark stains, dull pins and loose parts.
4. Clean the contacts with isopropyl alcohol or contact cleaner and let them dry completely.
5. Replace heavily oxidized cables and connectors instead of trying to restore them. In Phase 1, the original oxidized cables were replaced with new cables.
6. Protect the contacts with the chosen product, applied in a thin layer, according to the manufacturer’s instructions.
7. Isolate the variable. Before reinstalling the antennas, connect the base station directly to the CPEs by cable, with attenuators, as in Set up a TVWS test bench with attenuators. If the link works well this way, the earlier problem was in the connections.
8. Measure again and compare with the earlier value. Measurement points along the signal’s path help identify where there is still loss.
9. Seal the outdoor connections with self-amalgamating tape, covered with electrical tape, to keep water out.

See also

• Measure the loss of a coaxial cable with the NanoVNA
• Why a radio link has a shorter range than predicted