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Old 29-Feb-2016, 7:13 PM   #7
rabbit73
Retired A/V Tech
 
Join Date: Aug 2012
Location: S.E. VA
Posts: 2,747
Quote:
Probably because using the splitter creates a loss or 3db.
Not true.

When you use a splitter in reverse as a combiner, the loss is about 0.5 dB, which means that the most gain you can get when combining two identical antennas aimed in the same direction is 2.5 dB. When a splitter is used as a splitter, the loss about 3.5 dB because you are dividing the power in half.

It is possible to make a lower-loss combiner by connecting the coax lines from each antenna in parallel, which gives 37.5 ohms. This can be converted to 75 ohms by using a quarter wave matching section of 50 ohm coax.

It is also possible to make a half-wave coaxial balun that has less loss than a conventional ferrite core balun.

Any losses between the antenna and the input of the preamp subtract directly from the antenna gain.

Calaveras at AVS Forum used the parallel combiner and half-wave coaxial baluns for the lowest losses when combining his two 91XG UHF antennas.
http://www.aa6g.org/DTV/index.html
http://www.aa6g.org/DTV/ABD/Antenna_Block_Diagram.html

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Last edited by rabbit73; 29-Feb-2016 at 7:56 PM.
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