Stacking Principles

Stacking with Coax Stacking with Power Splitters

Stacking with homemade Power Splitters (DK7ZB)

Splitters available by DJ3MF, e-mail:


The basis of the power splitters/combiners is a construction of a square tube for the outer conductor and a round tube for the inner conductor. It forms a quarterwave coaxial impedance transformer.

The relation D/d influences the resistance/impedance of the splitter.

As with the stacking by coax-cables the impedance transformation will be made with lengths of lambda/4.

A halvewave-splitter consists of two quarterwave-splitters in parallel.


A very good tool to construct power splitters is the program "AppCad" .The program is freeware, 

                                       download at

This is a screenshot of "AppCad", you can calculate all parameters for the construction of a power splitter.

ZE = Z02 / ZA

Z = Z0 (see AppCad)


Types of power splitters

The λ/4-power splitter (2-way) = Type 1a

 The λ/4-power splitter (4-way)= Type 1b

The λ/2-powersplitter (2-way) = Type 2a

 The λ/2-powersplitter (4-way) = Type 2b

The λ/4-power splitter (3-way)= Type 1c

Attributes of the Power Splitters

Type Ways Length ZE ZA Z0
1a 2x λ/4 25 Ω 50 Ω 35,4 Ω
1b 4x λ/4 12,5 Ω 50 Ω 25 Ω
2a 2x λ/2 50 Ω 100 Ω 70,7 Ω
2b 4x λ/2 25 Ω 100 Ω 50 Ω

Lengths of the inner Tubes (d) for the Bands 2m, 70cm and 23cm

Amateurband Principle Length inner tube
2 m λ/4   520 mm
70 cm λ/4   173 mm
23 cm 3λ/4   189 mm

What dimensions you use for D and d depends on the sources you have in your country. 

Use AppCad to calculate suitable power splitters. For Germany I have some combinations in the tables:

Table 1: λ/4-Splitter , 2-way, Type 1a, needed Z=35,4 

Type Square Inner (D) Round Tube (d) Z
1a 30x2 mm 26 mm 15,5 mm 35,6 Ω
1a 29,5x2,4 mm 24,7 mm 15 mm 34,4 Ω
1a 23,5x1,5 mm 20,5 mm 12 mm 36,6 Ω
1a 19,5x1,5 mm 16,5 mm 10 mm 34,6 Ω
1a 30x2 mm 26 mm 15 mm 37,5 

Table 2: λ/4-Splitter , 4-way, Type 1b, needed Z=25,0    

Type Square Inner (D) Round Tube (d) Z
1b 25x2 mm 21 mm 15 mm 24,7 Ω
1b 19,5x1,5 mm 16,5 mm 12 mm 23,7 Ω

Table 3: λ/2-Splitter , 2-way, Type 2a, needed Z=70,7     

Type Square Inner (D) Round Tube (d) Z
2a 29,5x2,8 mm 24,7 mm 8 mm 72,1

Table 4: λ/2-Splitter , 4-way, Type 2b, needed Z=50     

Type Square Inner (D) Round Tube (d) Z
2b 30x2 mm 26 mm 12 mm 50,9
2b 25x2 mm 21 mm 10 mm 49

Table 5: λ/4-Splitter , 3-way, Type 1c, needed Z=28,9 

Type Square Inner (D) Round Tube (d) Z
1c 25x2 mm 21 mm 14 mm 28,9
1c 29,5x2,4 mm 24,7 mm 16 mm 30,6

The 2-m-splitter Type 1a with two precision resistors 50 Ohm by R&S shows a SWR of 1,01 at 144,3 MHz and 50,6 +/- j0 Ohm (see Marker 2).

Built with 30x2 mm and 15,5 mm

Practical Construction

It is not easy to connect the inner tube to the coax-sockets. The best way for all materials (you cannot solder aluminium!) is shown in the pictures below:

Splitters built by Piotr, SP5MG

The measured data of the splitters by Piotr, SP5MG