The stacker is a device which is used to split power between up to three antennas. It can be used to switch antennas in a stack or for beaming multiple directions. A stacking system that is made this way is simply an aproximation of a two way and three way stack. The UN-UN transformer has got a ratio of 2.25:1 and that way you will get about 56 ohm with two 50 ohm antennas connected and 37.6 ohm with three antennas connected. That gives you a reasonable SWR in both cases. You can also use it as a regular antenna switch for three antennas and of course it is switchable between these different modes.
I recommend using a FT240-61 core to wind the UN-UN transformer. If you are using legal limit power levels then one core is enough but going over 2kW I would recommend using two cores. If you want to use the stacker on all HF frequencies I would recommend that you wind it five turns trifilar (three wires in parallel) around the core with copper emelded wire. If you wish to optimize it for 10m I would recommend using 4 turns and if using it on low (80,160m) frequencies I would recommend 6 turns. Make sure that the wires are in parallel so that they do not cross over each other anywhere and then remove the varnish and solder them straight down at the UN-UN position of the PCB.
To avoid breaking up the ground plane of the PCB you must solder wires from the input control lines to each relay, but this is clearly marked out on the PCB. The relay which is named K5 is optional. The idea of this relay is that any unused antenna is grounded so that you increase the isolation between the ports and it should be switched together with the IN relay. Note that there is a small mistake on the PCB. Under the K4 relay the capacitor is only connected to one side of the relay coil. So just solder a wire over to connect it together, it is shown on the pictures below.
As the other boards it is at least 105um copper and can handle > OM-3500 power levels without any problem.
List compiled by G4AON if ordering from rapid (note it’s for the 6×1 but most parts match)
Top view of the board – If used as a drilling template, make sure to print it as 1:1 scale.
| Ant combination | A (K2) | B (K3) | C (K1) | K4/K5 |
| A | 1 | 0 | 0 | 1 |
| B | 0 | 1 | 0 | 1 |
| C | 0 | 0 | 1 | 1 |
| A+B | 0 | 0 | 1 | 0 |
| A+C | 0 | 1 | 0 | 0 |
| B+C | 1 | 0 | 0 | 0 |
| A+B+C | 0 | 0 | 0 | 0 |
