Adapters for Antenna Cables
Connectors and Adapters Insertion Loss
Loss of signal power caused by the connection between an RF device and an RF cable across a connector is called insertion loss. It is calculated and expressed in decibels (dB).
Insertion loss is attributed to three main causes:
- Dielectric loss- power loss in the dielectric material.
- Copper loss- heat dissipated at the conductor’s surface (skin effect), relative to main conductor and metal plating used.
- Reflected loss- reflected energy lost in the direction of transmission.
Different connectors have different insertion loss rating, depending on the dielectric material used, the level of shielding and frequency used. For example, a BNC connector is rated at a 0.2dB maximum loss at 3GHz, an SMA and RP-SMA connector has a 0.06dB loss at 6GHz, N-type connectors are rated at 0.15 dB at 10 GHz.
Insertion loss rating for most connectors is usually given at a single optimum frequency due to the complexity of precision testing for such low values at different frequencies.
Using connector adapters to interface antenna cables and devices using incompatible connectors increases the insertion loss due to the extra connections. Most connector adapters have an insertion loss of 0.1dB at the optimum frequency. Adding an adapter to a connection line also adds to the sum of insertion loss.
Differences in the choice of metal housing for connectors and adapter (stainless steel or brass) only affects the durability of the connector. Choice of plating metal; gold, silver, and nickel determines the conductive and durability characteristic of the contacts. Collectively these characteristics may affect insertion loss but not in a significant way.