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If you do not want to go through the bother of making physical filter and combiner networks with exact dimensional requirements, you can put amplifiers in the signal path from each antenna and then accept the small losses from combining networks. You can then combine them with less perfect methods, such as resistor splitters (6 dB loss per stage which is overcome by the amplifiers described above) If these are very strong broadcast signals, you could probably not use the amplifiers and only the resistive combiner.
Mini Circuits http://www.minicircuits.com/ makes many components that you can use. They sell small quaitities to the public. You can use their through hole parts and solder coax to the pins and ground to string them together.