Tobias (DH1TW)

2 minute read

One of last years projects was the improvement of our Contest Station ED1R. For the various Yagis we needed smart ways to combine antennas. Instead of buying commercial stackmatches (antenna combiners) I decided to build them up buy myself and adjust them to our needs.

HF part

A great resource is Mike’s, SM2WMV (SJ2W) website. Mike is a professional RF engineer and he designed beautiful Stackmatch PCB’s which he also makes available for purchase. Instead of spending hours in designing my own stackmatch PCB, I preferred to buy Mike’s PCBs – especially at this price – a no-brainer.

Stackmatch PCB with Transformer

Basically all I had to do is purchasing the missing components, drilling the holes in the box and installing everything. I used two stacked FT240-61 ferrit cores for the transformers. All the transformers consist of 4 (10m & 15m) or 5 (20m & 40m) trifilar windings of 2mm enameled copper wire. Since impedance is very low (17 – 50 Ohm), no high voltages are expected. That’s why no additional (e.g. Telfon) insulated wires are necessary.

Stackmatch PCB with Transformer and Delrin washers

In order to fix the Balun properly on the PCB I purchased from Hans, DK3YD high temperature resistant Delin washers.

Stackmatch housing

Above you can see the aluminium box I bought at the local electronic store. The PCB fits perfectly into the box.

Stackmatch housing outside

and for outside.

Stackmatch assembled

This is how the stackmatch looks assembled

Measurements

S11 Measurements with 50 Ohms terminated - all ports

S11 between the Input and the Output Ports is always better than -20dB (click to enlarge)

S21 Port Isolation - Antenna1

Isolation between the ports is between -60dB (7MHz) and -40dB (28MHz) (click to enlarge)

S21 Antenna2 - with Antenna1

S11 and S21 of two antennas combined (3dB Splitting) (click to enlarge)

S21 Antenna 3 - worst case

S11 and S21 of three antennas combined (6dB Splitting) (click to enlarge)

Stackmatches installed

shack1

And finally all the stackmatches installed at ED1R above the 8-Pack and the 4O3A High Power Bandpass filters

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