Why do cables have F connectors?

Yeah, you know what we’re talking about. The “F” connector is that screw-on connection used for your antenna, satellite and possibly even your cell booster. It’s so common you probably don’t even think about it. Before the coming of the internet, it was the most common connector in homes.

History of the F connector

The “F” connector doesn’t seem to have been named for anything (unlike the “N” connector for example which was named for its inventor Paul Neill.) If may have been named because it works for RF, UHF, and VHF, which all have the letter F in them, but that’s just speculation. What is known is that it was invented in the 1950s and became common on TVs when antennas started using 75 ohm cable.

Prior to the “F” connector, most antennas used twin-lead 300-ohm cable. Twin-lead cable had the advantage of having a similar impedance to the antenna itself. That meant no electronics were needed to change the characteristics of the cable. Today we don’t really worry about that, but in the days before transistors that was a very big deal. The package that sits in your antenna with a little bit of circuitry on it doesn’t even register with you today. That’s because it’s so small. In the 1940s it would have been huge and far more delicate. It also would have been made by hand and quite expensive.

Another option in the 1950s was the so-called UHF connector, also known as the PL-259 or SO-259 connector whether it was male or female. This was also a fairly compact connection but nowhere as easy to make as the “F” connector.

In the UHF connector, the center houses a sturdy pin which makes a more durable connection but also somewhat more prone to loss or poor connections. The UHF connector is still used in some radio applications, but I haven’t seen one on a television since the 1980s.

Advantages of the “F” connector

The “F” connector has a lot going for it. Because it uses the center conductor of the cable as its center pin, it’s both less expensive to make and provides a slightly better signal. Its screw-on outside makes it secure and watertight when used with weather boots. The connector itself forms a good shield.  Push-on type connectors are the exception here, which is why push-ons are not used for satellite or other high-frequency use.

In addition to all that, the “F” connector takes up less physical space. Compared to the larger connectors used in the 1940s and 1950s, the F connector seems quite compact actually. The F connector is similar in size to an RCA connector (the one used to connect audio devices.) However the F connector has better shielding and better performance. What’s not to like?

Uses besides antennas

Antennas and satellite systems use F connectors, as pretty much all of us reading this article know. Consumer cellular boosters use F connectors, because it’s a comfortable and familiar connection. Commercial systems use 50-ohm cable with N connectors. Commercial grade 50-om cables like LMR400 have less loss than 75-ohm cables, although not every 50-ohm cable has less loss than a similar 75-ohm cable. Less loss means that longer runs from antenna to booster are possible.

Over the years there have been some wacky uses of the F connector. Some early networking schemes used it. More commonly, networking cables usded the BNC connector or some proprietary cable in order to make an easily removable connection. While the F connector can carry some power, it’s not good for more than 40 or 50 volts and a few amps due to the thin center conductor and dainty outer braid. Still, as any satellite fan knows, coaxial cable carries power quite easily.

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