- jacks, plugs and sockets

With so much discrepancy in connector terminology today, you can be forgiven for being a bit unsure. Moreover, the type and gender is often just represented by initials in product codes. Confusing? Well, it shouldn’t be – if we all follow the rules...

Most will have come across sockets, slots, receptacles, and outlets denoting female connectors and jacks, plugs, prongs and pins for males and part numbers ending in M or P for male or F or S for female versions. The terms jack and plug can mean almost anything nowadays. But they don’t.

Correct terminology for connectors is defined \ in the ANSI Y32.16 2008, which is the current American Society Mechanical Engineers standard covering the formation and application of reference designations for electrical and electronics parts and equipment. This standard replaces the former ANSI Y32.16 and the withdrawn IEEE 200-175.

ANSI &32.16-2008 just documents what has been accepted convention for many years but has since become confused by many.

Officially, jacks are used on fixed (or less moveable) equipment like radios and plugs are used on less fixed (more moveable) items like wires, cables and the like. Therefore, a connector on a transceiver (less moveable) will be a jack. It’s counterpart on a coaxial lead (more moveable) will be a plug. Initially speaking, P represents Plug and J or X denoted Jack. Where two cables are connected together, both connectors will be plugs.

Top to Bottom: N male, N female, PL259, SO239

While this definition is exclusive of gender, there are some conventions that do exist. Jacks are often female and plugs male, as it is usually more practical (and safer with higher power applications) to have the more moveable connector plug into a fixed socket (as in electric power connections). However, this is not always the case. The gender of a connector is determined by its primary features, exclusive of covers, shields, handles and the like: the male connects, plugs or screws into the female. Connectors that have paired identical parts with both protrusions and indentations, (eg SAE and jackhammer air hose connectors), have a number of names including hermaphroditic, genderless, combination, two-in-one or two-way connectors. There are also connectors with male and female connectors on opposite ends, designed to be placed between a male and female to intercept a signal or take power. These are also known as hermaphroditic and may also be called vampire or parasite plugs. Video coaxial cables often have a connector with inner pin and outer fixed or rotating shell, which are normally considered to be male.

So, in order to avoid confusion and ensure we’re all on the same page, it’s normally best to use Jack and Plug for the function and Male and Female for the gender.

There are a number of connection methods.

Bayonet types provide a sturdy connection which survives slight pulling of the cable or repeated moving. The strength of the joint relies on the shear strength of the pins and the strength of the slots which hold the pins in place when locked.

Because of the connection mechanism, Compression Gland types only suit a limited range of cable sizes. The centre pin of the connector (usually solder type) and the braid and sheath of the cable are held by an expansion compression gland and a nut at the rear of the connector. They need no special tooling, so are ideal for use in small quantities or in one-off requirements.

While Crimp types are faster to assemble and ideal for large numbers. However, greater accuracy is required, as they cannot be reworked, and precision tooling is required. Crimp on terminals are attached by inserting the stripped end of a stranded wire into a part of the terminal, which is compressed tightly around the wire.

Threadedcouplings are more rugged and can be tightened sufficiently to enable a good low resistance connection between the two halves. Consequently they are more reliable at higher frequencies.

Greater performance accuracy and higher frequency handling is provided when connectors are designed to have constant impedance and individual cable formats. UHF (PL239/SO239) connectors do not fall in this category, so while they are economical to use, their use is limited to frequencies below 300 MHz. BNC, TNC, N and C types have this advantage.

C types were designed for higher power applications with quick mating and release and are basically a bayonet version of the N type with two stud bayonet lock. They are not in common use today. Although they are generally weatherproof it is wise to provide protection for external use.

BNC connectors are a miniature version of the C type. They are both rugged and compact and have a bayonet connection. They can be used in a wide number of applications where coax or screened cable is required, from RF to oscilloscopes, audio generators and power meters up to 4-10 GHz depending on individual specifications.

The more rugged threaded connection of the TNC type, which was developed to overcome vibration problems, makes it possible to operate up to, say, 11-18 GHz.

N type connectors, which are slightly larger, were developed to provide higher performance. They also have a screw connection and can operate up to around 11-18 GHz.

Some connector types offer a choice of connection method. BNC, and TNC connectors are also available in compression gland and crimp types as well as bayonet.

Designed in the 1960s, the SMA type is a sub miniature connector which is often used to provide RF connectivity between boards and for microwave components like filters, attenuators, mixers and oscillators. They have a hexagonal threaded outer coupling that can be tightened with a spanner. For flexible cables, the frequency limit is normally determined by the cable not the connector. Usually they can handle up to around 12 GHz with special high quality version up to 18 GHz with some claiming up to 24-26 GHz. (to be continued)

The F type connector was invented in the 1950s and came into its own in the 1970s on VHF, and later UHF, television antenna connections, when coaxial cables replaced twin-lead. It uses the solid wire conductor of the specified types of coaxial cable as the pin of the male connector, and is not corrosion resistant unless it is designed to be waterproof. Therefore it is important to be assured of quality design and manufacture. They are available to fit a limited number of cable sizes. The male can be crimped or screwed, while the female is generally screwed.

It is the least expensive, general purpose connectors with non-constant impedance for use at 500 volts or less, and for use with low frequencies to 500 MHz. It generally has good 75 ohm impedance match up to around 1 GHz. New higher performance F type connectors are coming onto the market to handle the latest high speed cable modems and customer interface units.

FME connectors are very useful in mobile antenna applications where there are a myriad of proprietary RF connection types especially on mobiles phones. Generally it is possible to source an adaptor to FME from the manufacturer or phone supplier to facilitate connection.

LC Male LC Female

LC and LT threaded connectors are designed for use in high power high performance connections, as are often required in military installations, and are designed to suit different cable types, including RG, M17 and semi-rigid cables. LC series are often used with RG17 and RG18, and LT with RG117/U and RG118/U. When mating with older types, it is necessary to check compatibility. The frequency range for LC types is up to1 GHz, and up to 2.5 GHz for LT connectors with a 5,000V peak voltage rating. Models are also available with counter bored, overlapping insulators for a peak voltage of 10,000V, and with aluminium bodies for weight reduction. Mating surfaces of insulators need to be coated with suitable silicone ignition to achieve the rated voltage capability.

Of course there are many types of connectors in use today and, as new applications come about the number grows. There is, however, one piece of advice that never changes. While the connector may be the smallest member of the RF chain, it plays a critical role in achieving required standards of performance. One lossy connector can spoil everything. Never scrimp on connectors.