A cost effective current-mode 1:4 balun can be constructed from two lengths of coax, two ferrite rods, some electrical tape, cable ties, a length of PVC water-pipe and some connectors. This form of 1:4 current-mode balun is named after G. Guanella.
(see the optional link in Figure 1).
Ideally the transmission lines should have a characteristic impedance of half the balanced load.
I have found that this balun is superior to the normally documented voltage-mode transformer or Ruthroff balun. The Guanella balun has perfect winding or transmission line symmetry with respect to the balanced load.
It is easy to wind the coax onto the ferrite rods. Experimental data supports 5 turns for coverage between 3 to 30 MHz, however if you want to operate at 1.8MHz I have found that about 10 to 15 turns are required. The turns can be held by insulation tape and by applying two cable ties on the ends of the last layer on each rod. The low impedance end is terminated at a coaxial connector by taking the two centre-conductors in parallel to the centre pin and the two braids in parallel to the ground pin. On the high impedance end the top centre-conductor and the bottom braid are connected to the load, while the top braid is connected to the bottom centre-conductor - this junction can be grounded to force symmetry in the load.
The two balun sections can be housed in PVC water pipe. Cut a section large enough to make two end pieces which can be flattened with the aid of the heat from a hair-drier or heat-gun. The circular end-sections can be cut with tin-snips. I drilled a hole for a panel-mount connector in one end and used banana connectors for the balanced feed on the other end. The end sections should be inserted inside each end of the pipe and held in place with the PVC pipe glue, but I have also found hot-melt glue adequate and easily removable. Extra protection is obtained for the ends if you leave an overhang by inserting the ends further into the pipe.
Transmission Line Transformers, Jerry Sevick, W2FMI, 2nd Edition, ARRL.
A Cost Effective Current-Mode 1:1 Balun, Ralph Holland.