For this installment of Kit Corner I’d like to share a build I’ve been using for quite some time both at the home QTH as well as on some of my POTA activations. The 4S-Tuner Kit designed by N0MS and offered through 4sqrp.com
The 4S-Tuner is a classic T-Match tuner for random wire and EFHW antennas with a two LED SWR indicator. It will tune 80 Meters thru 10 Meters at 10 Watts of power. Making this an great addition to any QRP kit builders shack or portable kit.
Like many of the designs and kits by David Cripe (N0MS) this is a ‘Pittsburg Construction’ kit that uses a surface mount board design that is populated with through-hole components.
With this design the components are prepped prior to installation by bending the legs up in a ‘W’ shape. Solder is added to the pads first then you can install components by using your soldering iron to remelt the pads and a pair of pliers or tweezers to hold the component in place. This construction method goes pretty quickly once you get the hang of it. With these kits I find pre-soldering all the pads as a first step speeds up the assembly a bit and is easier to do without other components in the way.
The case for the project is made from PCB’s and is held together by soldering the corners and seams. This helps create a shielded case that is quite solid once completed.
There is one toroid in the kit to wind, which is wound and soldered through the contact lugs of a rotary switch. Winding the toroid together with the switch helps hold the wire in place, making it one of the easier toroids to wind that I’ve done in a kit and making it an excellent introduction to toroid winding for beginners.
Connections for the transceiver is BNC and for the antenna you have your choice of binding posts for wire antennas or a BNC connection.
Operation is fairly simple, start with the indicator switch in the ‘OUT’ position and select an induction value on the center knob, adjusting the right and left capacitance knobs for the most band noise. You then use your transmitters Tune mode and switch the indicator LED’s to the ‘IN’ position and adjust the right and left capacitor knobs again until the Red LED is completely extinguished and the Green LED is fully bright. At that point the SWR should be around 1:1. You can then turn off the tune mode of your transmitter and move the Indicator switch back to the Out position and operate your radio as desired or try again with a new inductance value if you did not get a 1:1 with that value.
This Tuner has served me well both at home and on multiple POTA activations where I tend to use End Fed antennas of various makes. Below is a picture of the unit in operation (on the far left) running FT8 with the QRPGuys AFP-FSK Digital Transceiver III that I covered in an early edition of Kit Corner and a Raspberry Pi. I would encourage anyone in need of a QRP tuner to check it out.
