The most popular backpack or SOTA HF antenna must be the Halfwave. its very cheap . Just a length of wire, but it gives us problems as its a very high impedance load for our radio. This little ATU will allow you to match a halfwave wire to your radio , will work with halfwave wires for 40 to 15m.
The unit has a built in SWR indicator LED and resistive bridge to allow risk free tuning protecting you finials from a high SWR as you set things up.
Easy project to build with just one core to wind thanks to using a resistive SWR bridge