Connectors: BNC, TNC, SMA, MCX, MMCX, IPEX/U.FL — what's this alphabet soup?

Lost? Use the clue

Connectors are divided into housing connectors (those on the receiver or antenna housing) and board connectors, which are mounted on the printed circuit board. Housing connectors include BNC, TNC, and SMA, while board connectors are MCX, MMCX, and IPEX/U.FL. The board with the housing connector is connected by a wire called a pigtail.

The main difference between board connectors is that they are only good for about ten uses. That is, you assemble it, plug in the pigtail, and that's it. Housing connectors are good for hundreds or even thousands of insertions and removals. If you want to have a stationary antenna and test receivers with it, use TNC connectors and thick, expensive coaxial cables. If you occasionally want to change antennas and use cables 1-2 meters long or less, SMA will work just fine.

As for board connectors, anyone can insert them. But removing them... Several times, instead of pulling out the pigtail, the MCX connector simply detached from the printed circuit board. In short, there is little force involved, and you need to know how and where to apply it.

Some connectors have an RP (Reverse Polarity) version, which differs in that the male and female parts are swapped relative to the inserted (screwed-in) part.

And when choosing a connector, don't forget that it must be compatible with both the impedance and the diameter of the coaxial cable. Otherwise, there will be significant losses in the connector.

BNC. The full name is Bayonet Neill Concelman. Invented in the 1940s by the company Amphenol and named after the company's engineer Carl Concelman. As the name suggests, it is a bayonet connector. It is probably very familiar to many people from oscilloscopes. It is still in use, for example, in Garmin navigators. 

TNC stands for Threaded Neill Concelman. It's a newer connector by the same author, as the name suggests, it's threaded. The main workhorse for long cables. The fact is that in order not to dissipate the weak GNSS signal, a long cable must be thick enough. Thick cables connect well with large BNC and TNC connectors. In the picture (Photo at the top of the page), on the left is the threaded TNC, and on the right is the bayonet BNC. Both can have 75-ohm impedance and 50-ohm impedance. For GNSS, usually 50 ohms.

RP-TNC, also known as RTNC. This is for understanding what Reverse Polarity is. On the left and right are the male connectors, the screw-on part. But on the right with a pin, i.e., "male" (regular TNC), and on the left with a hole - "female" (RP-TNC).

SMA stands for SubMiniature version A, developed in the 1960s. This connector is designed for 500 cycles, but only when using a torque wrench with force control. SMA is always designed for 50 ohms and relatively thin cables. In the photo, there's a socket with a hole, i.e., "female." With RP-SMA, on the contrary, "female" (hole) will be on the male connector, and "male" (pin) in the socket.

MCX (micro coaxial connector) and its miniature version MMCX (micro-miniature coaxial) were developed in the 1980s. In the photo, you can clearly see how small the MMCX connector is. It's a snap-on connector, usually 50 ohms, used as a board connector.

U.FL is a connector from Hirose Electric Group, similar connectors from other companies are called I-PEX MHF, IPEX, IPX, AMC, UMCC... It was invented in the 1990s and is even smaller than MMCX. It's also exclusively a board connector, and only 50 ohms. 

I think now it's clear how to understand the purpose of an antenna by its connector?

• BNC and TNC are for stationary or geodetic antennas, with long and thick cables.
• SMA is for short cables or directly on drone connectors.
• IPEX, MCX, and MMCX are for mounting inside devices.

© Eltehs SIA 2023