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Difference between a Tap and a Splitter? Tap vs Splitter

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Difference between a Tap and a Splitter? Tap vs Splitter

Bài gửi  duyminh on Fri Dec 18, 2009 5:44 pm

Difference between a Tap and a Splitter? Tap vs Splitter

A tap is used when a cable needs to feed TVs in one location and then continue downstream to more locations. Hallways in schools are a good example. The cable (called a "trunk" at this point) will hit a tap to feed a block of four rooms. The cable connected to the output side of the tap will run down the hall to the next block of four rooms where another tap will be inserted, and so on to the end of the hall. The closest taps have the highest attenuation, while taps at the end of the hall have the lowest attenuation.

A splitter divides the input between two or more outputs. It is a "dead-end" device. In the above example it would be used at the end of the hall to feed the last rooms.

Taps are rarely used in homes. Most home systems use a single splitter near the demarc (point at which the cable enters the house) to feed all of the drops.

A splitter will cut the signal by 3.5 dB at each output for every doubling of ports. IOW, a two-way will cut -3.5dB. A four-way = -7 dB, and so on. For this reason, a broadband amplifier is used before the input of the splitter to compensate for the splitter insertion loss.


All depends on the size of the system. If its only 4-6 ports then splitters are fine, if its larger then you may be in the region of using taps. Taps require that the signal from the LNB is pumped up 15-20dB before you start, then the tap can drop the signal by the nature of the tap some 10-20ddB as specified to each face plate.

The advantage of a tap system is that is gives greater isolation from each face plate to the main backbone of the system, hence less glitting due to the action of other users.


RF Video Distribution Concepts
Integrity of RF Signals
There are two parts to maintaining the integrity of RF signals; The first part is keeping your signals from leaking out of the cable. The second part is keeping outside signals from leaking into the cable (called "ingress".) When your signals leak out of the cable, it can cause interference on your neighbor's TVs. Besides, it annoys the FCC. If a local broadcast channel leaks into your cable, it will interfere with that channel (though not necessarily the same program) in your distribution system. Both problems are avoided by using good quality RG6 coaxial cable and properly installed high-quality connectors.

Splitters, Combiners, & Taps, Oh My!

RF cables are designed to carry RF signals from one point to another, not from one point to many. In other words, you can't run RF signals to multiple locations by wiring all the destinations in parallel. The reason is that the residential RF distribution scheme is based on 75 ohm terminated transmissions. Meaning that the transmitting side expects to see one, and only one, 75 ohm load on the other end of the cable.

A splitter is a small device that has one input (the 75 ohm load) and 2 or more outputs, each driving a separate 75 ohm load. Essentially they are transformers that split the power in the input signal to multiple outputs, while maintaining the 75 ohm impedance. However, there is no free lunch! Every time you split an RF signal with a splitter, you drastically decrease the signal's strength. An RF signal only has so much power. Logic dictates that splitting this signal in two with a "passive" device will result in two signals that each have--at most--half of the original signal's strength.

A combiner is simply a splitter hooked up backwards. It combines the channels on two or more separate cables onto one cable. The only drawback to this piece of magic, is that the cables being combined cannot have any channels in common with each other. The resulting signal on that channel would be trashed.

Combiners make some neat things possible. Let's say you have cable TV that has channels 2 through 63. And you have a DSS receiver that you would like to be able to see on any TV in the house. You can hook up a modulator to the DSS receiver, set the modulator to channel 65, then combine this new channel back in your wiring closet with the cable TV coming in! Now any TV can watch DSS by simply changing to channel 65. This concept of "in-house" channel generation, together with the new cheaper and more reliable digital modulators, is opening up many new possibilities in residential video distribution.

Taps are similar to splitters, but are "wound crooked" so that the outputs are not equal in signal strength. The "through" output of a tap may only reduce the signal level by a very small amount, while the "tap" output is a small fraction of the signal level. Taps are primarily used in complex commercial distribution installations.

Attenuators are simple "one in, one out" devices that reduce the signal strength. Attenuators come in various sizes and are useful when tuning up the video distribution system.

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