Self Supported

4-Square for 80 / 75 M - Tuning Stub

The tuning stub provides an easy method to resonate each vertical to exactly the same resonant frequency. The basic stub idea has been used in both VHF, UHF, and HF tuning solutions. The wire is spaced 12 inches, so that it's impedance is very high. It becomes a length of wire that can be adjusted by connecting a antenna analyzer at the feed point, and using a sliding adjustable short, resonating to an exact frequency. Once the positions of the short are found, a permanent wire can be soldered in place of this adjustable short. My stub consists of 2 pieces of 36 inch long 1/2 inch Schedule 40 PVC, along with 2 pieces of 14 inch long 1/2 inch Schedule 40 PVC, connected with 1/2 inch PVC 90 degree angles. I used # 6 AWG solid copper as the vertical wires, secured 12 inches apart in the PVC by drilling 3/16 inch holes spaced 12 inches apart on the 14 inch section. The copper wire is secured by soldering a wire loop at the ends, preventing the wire from slipping through the holes. # 14 AWG copper wire is attached at the bottom of the stub, with one wire feeding the bottom connection point to the aluminum vertical, and the other wire going to the coaxial connector.