What Is a RF Cable?

John Lister

An RF cable is a basic cable used primarily for carrying audio-visual signals. The name comes from an abbreviation of "radio frequencies." It is a type of coaxial cable, which involves a series of casings to protect the signal from interference.

An RF cable is a basic coaxial cable that is used for carrying audio-visual signals.
An RF cable is a basic coaxial cable that is used for carrying audio-visual signals.

The coaxial design used in an RF cable is designed to prevent potential interference. To counteract this, the coaxial cable uses four circular layers. From the inside to the outside they are: the wire carrying the signal; an insulating material which is usually solid plastic; a metal shield; and a plastic casing which protects the materials inside.

RF cables have a series of casings to protect signals from interference.
RF cables have a series of casings to protect signals from interference.

RF cables have several important drawbacks. It can only carry sound between two devices in mono rather than stereo. As well as being unable to produce a stereo signal, this also means it can't carry surround sound information broadcast in Dolby Pro Logic™. This means that if an RF cable is used, it is impossible to get true surround sound audio even when using a decoding receiver.

Another drawback is that while the design of the cable does block interference in theory, in practice this is often not achieved. Cables, particularly cheaply made ones, can be subject to interference from magnetic sources or power cables. This can lead to visible picture interference such as ghosting.

Most RF cables will simply slide into a socket and can be pulled out easily. Some versions involve tightening a cap, rather like a screw. These connections are more secure and less likely to work loose and lose picture quality, but are not as convenient as the standard RF connection.

While using an RF cable is usually the cheapest option, better quality cable choices are usually available at an affordable price. For this reason, the only real reason to use an RF cable is where no alternative is possible because the TV set or VCR does not have suitable inputs. It's important to note this guideline does not apply to the lead between a TV aerial, whether rooftop or indoor, and the TV equipment.

In this situation, an RF cable is still the standard option and will usually be hard-wired into the aerial. However, it is best to only use RF cable between the aerial and the first device it is connected to. For other connections, such as from a set-top box to a television, it is best to use better quality connections such as composite or component video.

How To Test RF Cable

Testing an RF cable is a simple process. However, you'll need some basic equipment: a multimeter. Also known as a volt-ohm meter, this device measures current, resistance, electrical voltage and other important performance details. Both analog and digital versions are available on the market today. You can find an inexpensive multimeter starting at $20. Advanced models can price as high as $130.

Checking Your Multimeter

Before starting your RF cable test, turn your multimeter on and adjust it to the resistance setting with the best resolution. For most models, this will probably be around 200 ohms. Make sure the meter's probes are connected, then test for internal resistance by touching the red and black probes together in their centers to form a cross. Make a note of this resistance reading.

Testing Your Cable

Once you have your multimeter ready, you can test your RF cable. Make sure the cable is not connected to anything. then perform your RF cable test by following a few basic steps:

  • Touch each probe to one end of the RF cable. Place the probe's tip on the outside of the inner ring inside the cable end. 
  • Check the multimeter's readout. Remember to subtract the internal resistance figure from your earlier test from the meter's measurement. The final result should be near 0 ohms. 
  • Touch the probes to the center pin in each cable's end. Check your reading and subtract your internal resistance measurement. This figure should also be close to 0 ohms.

Examine the two measurements you took during this test. If either one exceeds 5 ohms, you'll probably need to replace the cable. To test for shorting, keep one probe touching a pin in the cable end and touch the other probe to the outside of the inner ring in the opposite cable end. If there's no short in the line, the meter should read "1" for undefined or out-of-range resistance. If it reads anything else, you likely have a shorted cable.

Tests on Longer RF Cables

Longer RF cables require a slightly different testing method. For best results here, you should perform the multimeter test using only one end. Touch one of the meter's probes to the center pin of one end connector, then simultaneously touch the other probe to the outside of the same connector's inner ring. An infinite resistance reading indicates that the cable's in good working order. Low-level resistance points to a possible short in the cable.

Do You Need an RF Cable?

For years, RF cables were the standard for transmitting video information to a television set. Since then, technology has rapidly advanced. Most TV models still have RF antenna inputs. However, they also have inputs for HDMI and sometimes DVI.

RF cables transmit lower-quality video signals than HDMI and DVI. If you're connecting other devices to a high-def TV, such as a newer console gaming system, using an HDMI cable is a better bet. You'll be able to take advantage of the best quality graphics your device has to offer.

In some instances, you may still need RF cables. For instance, if you have traditional cable TV service, you may have a set-top box. These often require coax cables to connect to the cable outlet. On the other hand, many cable TV providers also offer apps for platforms such as XBox, PlayStation, Googe TV and Amazon Fire TV.

How Many Kinds of Coaxial Cables Are There?

You'll find two primary types of coaxial cables on the market. They differ in impedance levels, which are measures of opposition to electrical current flow. There are 75-ohm cables, primarily used to transmit video signals. There are also 50-ohm cables, designed for data and wireless communications.

Coax Cable, TV Signal and High-Def TV

Keep in mind that coax cables can be used for many purposes. For instance, RF cables can carry HDTV signals. If you're using a set-top box with your TV, you should make sure that it can transmit HDTV signals over RF cabling.

Keep in mind that with a 4K cable box, you may achieve the best results by using an HDMI cable from the box's HDMI out port to your TV. Meanwhile, your TV must also be capable of 4K to get the full benefit. If your TV is not 4K rated, you'll receive the best quality picture the TV set can deliver. Dep[ending on your set, that may translate to 1080p With a standard definition TV set, you'll see video transmissions in 480p quality.

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Discussion Comments

anon996872

Do all televisions sold in the UK have an RF aerial socket as standard?

anon332496

RF cables can convey ATSC signal and therefore the 5.1 AC3 audio signal embedded in it.

gremlins

@Sandy12 – Good question. The only other reasons I can think of that anyone would want to use an RF cable instead of a different type of cable, like a digital coaxial cable, is that they can’t afford to buy a digital coaxial cable, or just don’t know how to connect their TV and other audiovisual equipment using anything other than an RF cable.

Sandy12

If RF cable is inferior to other types of cable, why would anyone use an RF cable if there are other options available?

bobcat60

Beware, I have noticed that is can be very easy to damage the screw type rf cable connector. There is a needle like part that plugs into the next machine that is extremely easy to bend, but not so easy to bend back. If it is not inserted exactly right when you start screwing it in, it can really mess up the connection. So, even though it is more secure when it is plugged in, if you do not have a steady hand a standard rf connector may actually work better.

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