BNC hembra SMA Macho Conectores coaxiales para radios

How to Connect Coaxial Cables in Radio

Coaxial cable is all over your home; it connects your TV to the cable and may even supply you with Internet. It's for all kinds radio-frequency wired transmission, and as a result there are a huge number of different connectors available.

What Kinds of Coaxial Connectors Are There?

You use a coaxial cable, commonly called coax, almost everywhere for a wide variety of uses and that means that keeping track of the connectors involved can be a full-time job. As with many other devices, electrical cables also have gender. The connector with the inner thread is the male, and you use this on cables and antennas, while the connector with the outer thread is the female and mounts on the stationary equipment. Some of the more common connectors include:

  • Type F: Found in most cable television systems, this is the format most people are familiar with. It rates for 75 Ohms impedance and features a 3/8 diameter 32 pitch threaded connector.
  • SMA: Similar in design to the F connector, SMA rates at 50 Ohms impedance and features a 0.250-inch 36 pitch threaded connector. It is very commonly for connecting antennas in RF coaxial installations.
  • BNC: Unlike many other connectors, BNC is not threaded. Instead it uses a two-stud bayonet design that combines excellent retention strength with quick release capability. It's also available at 50 Ohms and is thus electrically compatible with SMA.

How Does SMA Work?

Thanks to various rules imposed by the FCC, there are at least four different kinds of SMA connector. In addition to the standard SMA male and SMA female connectors, there are also RP-SMA male and RP-SMA female connections. RP stands for Reverse Polarity but does not actually refer to any electrical characteristics; it only refers to the physical interface.

  • SMA: SMA is the original standard and follows the same basic design as Type F. The SMA male features inside threads and a protruding center pin, while the female has outside threads and a sleeve to receive the pin.
  • RP-SMA: RP SMA is electrically identical to SMA. The difference is that the RP-SMA female features the protruding center pin and the RP-SMA male features the sleeve. This is because gender is determined by the threading, not the center pin.

What About Adapters?

There are several different kinds of adapter in use. One of the simplest is an adapter that connects SMA and RP-SMA, but there are a number of others. In cases where you need a quick release on your antenna it may often make sense to use an adapter that converts an SMA connector to BNC. That way you can use each interface to its full advantage, or simply mate two otherwise incompatible connections.

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