A diplexer can be used to combine the signal of a satellite dish and a over the air TV antenna together onto the same coax cable feed. This method cannot be used with HDTV satellite receivers.

Two diplexer's are required. One outdoors that combines the satellite signal and the antenna signal together and one indoors that takes the two signals back apart.
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To combine a non preamplified antenna and a dish use the power pass satellite port only diplexer SKU:135 outdoors and indoors. Outdoors connect the antenna and dish to the appropriate labeled diplexer ports. Indoors connect the satellite receiver dish signal input to satellite port of the diplexer and the antenna input connection to the antenna port of the diplexer.
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To combine a preamplified antenna system use the power pass both ports SKU: 136 diplexer outdoors.  Connect the satellite dish and antenna to the appropriate ports og the diplexer. Indoors use the same diplexer as used above SKU: 135 for the non amplified system. When using this method the preamplifier power supply/injector is not used. The operating power for the mast mounted preamplifier is supplied by the satellite receiver.
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For the best performance I do recommend a preamplifier for most diplexed systems.
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Best Regards,

Denny

TV Antenna Source

"Helping America Watch Free TV"