Coaxial Connector Types

Most amateur radio gear uses the so-called “UHF” connector (formally called PL-259 for the male side and SO-239 for the female side). The name is misleading because the connector is not designed for use at the frequencies we now call “UHF.” (What was considered “ultra-high” in World War II isn’t anymore.) It is not a 50Ω connector, and each connection made with one will suffer some signal loss, especially when used at UHF frequencies, such as 440 MHz (70 cm band). Nevertheless, because the connector is so common on amateur gear, if the site has few connections, such as a field site or a simple base station site, it makes sense to purchase coax with PL-259 (“UHF”) connectors.

N-type connectors are 50Ω connectors.

• The standard N connector (named after Paul Neill of Bell Labs) is about the same size as a UHF connector.
• The BNC (“Bayonet Neill-Concelman”) is a smaller version of the N connector with a bayonet-style attachment. BNC connectors are quick and simple to attach, but they can wiggle somewhat and leak RF. BNC is commonly found on some older HTs.
• The TNC (Threaded Neill-Concelman) is about the same size as the BNC, but is threaded, like a standard N connector, making it more secure than a BNC and less susceptible to leakage. The TNC connector is not common with amateur radio equipment but is often found on commercial radios and RF test gear.

Although UHF-type connectors (PL-259, SO-259) are available for Heliax/hardline, the N connector is more common by far when terminating Heliax/hardline. After all, if you’re going to the trouble and expense of installing hardline, it makes sense to use a low-loss, 50Ω connector.

In sites with many connections in the feedline, such as stations that have bulkheads, filters, and switches, consider using N-connectors throughout the system, and converting to UHF only at the radio and/or antenna as needed. This reduces the number of sub-optimal UHF connectors to just one or two.

The SMA (Subminiature version A) connectors are commonly found on HTs. SMA connectors are 50Ω connectors. The connector is small and not suitable for use with RG-8/LMR-400 or larger cables.