RF Coaxial Connectors: A Simple Guide

RF (Radio Frequency) connectors, also known as coax connectors, are used with coaxial cables to securely transmit radio frequencies from point-A to point-B. They are found in a wide range of applications including television receivers, two-way radios, Wi-Fi devices with antennas, and scientific measuring instruments. Knowing some basic information about the different types of RF connectors and their common uses can help you decide on the right RF connector for your custom cable assembly. In this article, we will discuss the various types of coax connectors and some important factors to consider.

What Is a Coaxial Cable?

To better recognize the role of RF connectors, we must first understand how a coaxial cable works. Coaxial cables are a form of transmission line, built to send radio frequencies from one place to another. They make excellent transmission lines for their four-part design that maintains minimal loss of signal and protects the line from outside radio interference. The four parts consist of a center core (inner conductor), dielectric insulator, metal shield (outer conductor), and a protective jacket. The space between the inner and outer conductors is called the “impedance.” When attaching a connector to a coaxial cable, it is important that the impedances of the two parts match, or else the line will not work properly.

Common Types of RF Connectors

RF coaxial connectors are attached to coaxial cables to continue the transmission and transfer it from one place to another. Good RF connectors should block interference and maintain a minimal loss of radio frequency between transmission lines. When choosing a good fit for your cable assembly, it is important to consider impedance, frequency range, power handling, size, and cost. Here is a list of common connector types and their defining characteristics:

BNC (Bayonet Neill-Concelman)

The BNC connector is fitted with a secure and quick-fastening bayonet mechanism which prevents accidental disconnection. It can be used in almost any RF equipment including RF test equipment, transmitters, and receivers. They are available with either 50 ohms or 75 ohms of impedance and usually have a frequency limit of 4 GHz but can reach up to 10 GHz in specialty top quality versions.

TNC (Threaded Neill-Concelman)

The TNC connector is a threaded version of the BNC. Bayonet fastening tends to introduce noise in certain environments, so TNC connectors have been created to provide low-noise reliable connections, especially in environments where there may be vibration. TNC connectors are available with 50 ohms of impedance and have a frequency limit of 11 GHz.

N-Type

The N-type connector is a high-performance option used in many RF applications, including in broadcast and communication equipment, power transmitters, and receivers. N-type RF connectors are larger than BNC connectors and have a threaded coupling interface which ensures that they mate correctly. They are available in either 50 ohm or 75-ohm versions. N-type connectors typically have a frequency limit of 11 GHz, but precision versions are available for operation up to 18 GHz.

SMA (Sub-Miniature A)

The SMA connector is half the size of the BNC connector and is often used for RF connectivity between boards, microwave filters, attenuators, mixers, and oscillators. They have a threaded coupling which offers a secure and reliable RF connection. SMA connectors are available with 50 ohms of impedance and have a frequency limit of up to 18 GHz.

SMB (Sub-Miniature B)

The SMB connector is even smaller than the SMA, making it especially valuable for inter-board or assembly connections within equipment. They also have a smaller snap-fit connector for quick mating and demating. The connector is available in 50-ohm and 75-ohm versions and has a top frequency of around 4 GHz.

PC (Precision Connector) Series

The precision series RF connectors provide a very high-quality series of interconnects for use where high precision is required. These connectors are often used in measurement applications, intended for very high frequency RF transmission lines. They are more expensive than the other types but can carry signals of up to 110 GHz. PC series connectors are typically available with an impedance of 50 ohms.

UHF (Ultra High Frequency)

The UHF connector, also known as the Amphenol coaxial connector, was originally intended for use as a video connector for radar equipment but later became used for a variety of RF applications. They have a threaded coupling which prevents accidental removal and enables them to be tightened sufficiently to offer a good low-resistance connection. The drawback of the UHF is that it has a non-constant impedance,roughly 35 ohms, that limits their use to frequencies of up to 300 MHz. Though UHF connectors are rarely used in professional applications, they are an inexpensive choice for CB operation, amateur radios, and some video and public address systems.

F-Type

The F-type connector is a good low-cost option which is suitable for use up to 2 GHz and was developed for domestic TV applications. These connectors use the coax center conductor as the main pin and maintain a constant impedance of about 75 ohms across the connector.

Choosing an RF Connector

Once you have found a suitable RF connector for your cable assembly, there are a few variations to consider. Do you require a male or female connector? Should the connector be straight, or right-angled to fit in a tight space? What plating fits the application and your budget? These are questions to discuss and consider when making your choice.

At ASAP Semiconductor, we are here to assist you with all your aircraft component purchasing needs. Our knowledgeable team can provide you with more information about RF connectors and/or other components and offer a competitive quote. We are available 24/7x365! Send a Request for Quote (RFQ) form today and get a custom quote in fifteen minutes or less!