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I have a 4 way splitter which has DC pass written on arrows that point in different directions . Does this mean that the splitter isn't a just a passive splitter and it needs power?

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A splitter takes RF power from an input and divides it up between multiple outputs. The splitters are designed to operate at a certain range of frequencies. For cable TV, this might be from 5 MHz to 900 MHz. The important thing to note here is the lower bound, 5 MHz. This splitter would block signals that are below 5 MHz. DC, or Direct Current, is low frequency power (perhaps less than 5 kHz). This low frequency component of the signal can easily be blocked by using a capacitor is series with the port.

Because your splitter says DC pass, it "passes" DC voltages/currents from its input to its output. This does not mean that the splitter is active. The splitter likely can operate without any power (it can be passive). The DC power, if passed, can be used to power circuitry such as amplifiers that are connected to the cable.

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This means that the splitter will allow DC power to pass through from the receiver to the source. This is typically required for satelite TV where the polarity is used to switch the LNB (Low Noise Block) between different bands (if I recall correctly, usually even/odd stations require reversing the polarity).

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DC PASS is required for ALL LINE POWERED AMPLIFIERS which are typically used in Satellite TV dishes and mast mounted TV signal amplifiers. For mast mounted TV signal amplifiers, you have a power injector with a DC block on the output port which feeds something around 12VDC up the coax to the amplifier. With satellite, the receiver sends the power to the dish pickup. Combiners are used to allow for multiple amplifiers, say you have a majority of TV stations coming from a direction and a UHF off 90 degrees from beam. This allows for a main and secondary antenna each w/amp. Or two satellites. –  Fiasco Labs Oct 13 '12 at 17:46
    
Splitters work under the same conventions, you might want to serve multiple receivers off one antenna or antenna system. You need a DC PASS to get the power up to the satellite dish pickup or mast mounted antenna. –  Fiasco Labs Oct 13 '12 at 17:51
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