Radio Frequency (RF)

RF is the oldest way to transmit video signals. It is used on TVs and VCRs to connect these devices to both terrestrial (antennas) and cable transmitions. Since cable TVs are provided using this type of signal, unfortunetly you won't find anything better than this to connect your cable TV to your TV or VCR. This kind of connection can be used to connect your VCR to your TV, but since nowadays all TVs have composite video inputs (RCA), you should use composite video to connect your VCR to your TV, not RF, in order to get a better image quality. We'll talk more about this on the next page.

RF cables are found in two flavors: 75-ohm coaxial and 300-ohm parallel. This second type was used by old terrestrial broadcasting antennas, but even this kind of antenna use the 75-ohm coaxial cable nowadays. You can install a 300-ohm cable/connector into a 75-ohm connector by using an adaptor, as we show on Figure 6.

On Figure 1 you can see the RF input on a TV set. On this connector you should connect you cable TV or your antenna, if you still use terrestrial TV. Since this TV set has composite video inputs (“Video In”) you should not use this connector to connect your VCR. We’ll talk more about this on next page.

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Figure 1: RF input on a TV set.

On Figure 2 you can see RF input and output on a VCR. The input is used to connect the VCR to you cable TV (or decoder) or antenna, and the output can be used to connect the VCR to the TV, but like we said, this connection shouldn’t be done nowadays, since you can use composite video to connect your VCR to your TV, which provides a better image quality.

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Figure 2: RF input and output on a VCR.

On computers RF connectors are only used on video capture cards, to allow you to record live TV shows on your computer, connecting this connector to your cable TV system or a TV antenna. Don’t use this connector to hook a VCR to your PC, since you can use the composite video connection which provides a better image quality.

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Figure 3: RF inputs for TV antenna and FM antenna on a video capture board.

On Figure 4 you can see a typical RF cable and connector, and on Figure 5 another kind of connector that also can be used on RF connection. The difference between them is that the cable connector on Figure 4 is meant to be screwed to the female connector on your TV or VCR, while the second connector, on Figure 5, don’t need to be screwed, just push it towards the female connector and it will fit.

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Figure 4: Typical RF male connector and cable (screw type).

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Figure 5: Another kind of RF male connector.

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Figure 6: Adaptor to convert 300-ohm RF input (“old type”) into 75-ohm, which is more used nowadays.

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