Designing a Combiner for VHF/UHF

Here's is one way of combining several antennas on VHF/UHF is by using a power combiner (or power splitter if you prefer to look at it from that angle). Using the principle of impedance transformation in a quater wavelength transmission line, a proper matching can be made between antennas and the downlead cable.

To build a RF combiner you need to design a coaxial quaterwave line, having a characteristic impedance Zo, determined from Zo^2 = Z1*Z2, where Z1 and Z2 are the impedances being matched. This is normally done by using tubing - round or square - with air as dielectricum.

Simple impedance calculation
The characteristic impedance for the two types of lines are:

a = the diameter of the inner round conductor.
b = the inner diameter - or side lenght - of the outer conductor.


Combiners for 144, 432 and 1296 MHz
2-way combiner for 144 MHz.
4-way combiner for 432 MHz.
2-way combiner for 1296 MHz.

Exact impedance calculation

See more : 2.4 GHz Power Amplifier - RF Power Meter -  UHF Power Amplifier