Basic knowledge about connectors

Basic knowledge of connectors

Plug or socket?

Plug: We always define plug as "pin (male)", unless otherwise specified
Socket: We always define sockets as "contact (female)", unless otherwise stated.

1 BNC plug (different anti-kink colours)
2 BNC socket
3 BNC built-in socket

It is often assumed that the gender of a plug/pin has something to do with the external connection. This is WRONG!

Correct is: The gender of the connector always refers to the inner conductor only.

The term "male" refers to a connector in which the centre conductor protrudes, while the term "female" refers to a connector that forms a sleeve around its male counterpart in the centre.

Alternative terms in English are 'plug' for male and 'jack' for female.

The only exceptions are the 'genderless' (hermaphroditic) connectors (e.g. from LEMO) and the
reverse connectors. Reverse plugs, for example, have the housing of a plug and the centre pin of the socket, reverse sockets have the housing of a socket and the centre pin of the plug.

What does "R" or "RP" mean before some connectors?

Reverse plug connections are often used to avoid polarity reversal and confusion. This is why almost all devices with WLAN antennas have reverse connectors. Cisco uses RP-TNC, Netgear and AVM RP-SMA and other RP-BNC vendors for their 802.11b / g / n / ac (2.4GHz and 5GHz) wireless routers and access points. In a laboratory environment, we recommend not using an inverse connector because damage can be caused by mixing reverse and normal connectors.

The picture below shows four SMA connectors. The plug on the right side is the normal SMA plug (male), while the second from the right represents the normal female jack. The second from the left is a reverse connector (R-SMA), because it has a normal male pin, but the external thread of a female connector.

Which connector fits which cable? 50 or 75 ohms?

Decisive in the first place is the characteristic impedance. Then the dimensions must fit: Outer diameter of the inner conductor and inner diameter of the outer conductor (shield). Only if these dimensions fit the connector, a constant wave resistance and thus optimal transmission properties is guaranteed.

What is the difference from coaxial to triaxial?

For triaxial cables, a second screen is arranged concentrically and isolated from the first screen. The outer shield serves to carry an operating voltage (cameras) or to shield sheath currents, as the inner shield is traversed by the return current of the line. Triax cables require special connectors.

Homogeneity of coaxial cables and connectors

How important is the quality of coaxial cables and connectors as well as matching the characteristic impedance of the cable?

The characteristic impedance is determined by the relative permittivity of the dielectric, the inner diameter of the outer shield (outer conductor) and the inner conductor (permittivity = permeability of the dielectric for electric fields compared to the vacuum).

If the outer shield is crimped incorrectly (if you use the wrong tool or the cable and connector do not fit together), the dielectric will be deformed, causing the diameter of the dielectric to decrease, which then results in a lower impedance. A lower impedance results in a part of the waves being reflected and thus a lower useful signal is available at the end of the coaxial cables. We can determine how high the reflection is via the SWR (standing wave ratio) (test optionally available for cable assembly).

With the connectors we use, the dielectric is protected in a precisely fitting tube and is not crimped during crimping. The impedance remains stable in the area of the connector.

Therefore, to create a high-quality coaxial cable, it is not only necessary to use the optimally matched connectors, but also to know the right crimping force and to use the right tools. Trust us to produce a first-class coaxial cable. For us, this is everyday work; we have perfected our manufacturing steps so that high and consistent quality is always guaranteed.

Magnetic or non-magnetic connectors

Although conventional connectors have a brass case and contacts of beryllium copper or bronze, and a coating of gold, but the intermediate layer under the gold contains small amounts of nickel, so that the connectors are still weakly magnetizable.

Non-magnetic connectors are made of materials with permeability μr close to 1. They are used wherever large field strengths are to be expected, e.g. in medical technology.

As a result, nonmagnetic alloys are transparent to the magnetic field, since no field distortions occur. In the case of cable assembly, special care is required here to ensure that neither impurities nor magnetic impurities occur during the assembly or during the subsequent cleaning.

Cables with copper conductors are not magnetic (Bedea LowNoise, Multiflex_86, Aircell-5, RG316 Habia), see non-magnetic cables.