The base (Figure 1) is made from a piece of fence picket. Wood fence pickets are about 5.5 inches wide. That is wide enough to mount the antenna components and still have a little room for mounting brackets if you need to mount the antenna on a mast. I used #6 wood screws for mounting parts of the antenna. The loop is attached to the wood base using two copper pipe clamps that have been reshaped to fit the ¼-inch tubing. These clamps are thin and can be easily flattened and reshaped using a heavy set of pliers. Try to use copper pipe clamps instead of aluminum clamps to avoid galvanic corrosion that can occur between copper and aluminum metals. Copper clamps will also facilitate soldering of connecting wires. Solder the clamps to the ends of the tubing then screw the clamps to the wood base using the holes that are already drilled into the ends of the clamps. Connecting wires can be easily soldered to these clamps rather than trying to solder them directly to the ¼-inch tubing.

The tuning capacitor is mounted in the center of the antenna. The electrical value of this capacitor was measured as approximately 4.66 pF. Each half of the split stator capacitor was measured to be approximately 11.27 pF. Placement of the capacitor itself is not critical except that lead connection lengths can be critical and cause large changes in the resonant frequency. So mounting the capacitor in the middle with short leads makes sense. Speaking of lead lengths almost all of the wires used in the antenna system need to be kept as short as possible. If you breadboard your design and then later make the final connections by shortening the wires it will normally change the input impedance significantly so make your breadboard as close to the final design as possible.

“L” brackets are used for mounting most of the components. The brackets are especially convenient for the antenna connector. They are easy to use for mounting the variable capacitors to the wooden base.

This particular antenna uses a split-stator capacitor (Figure 2) as the main tuning component. The split-stator design is not critical. A single gang capacitor could be used if it enables the system to be resonate at the desired frequency. The split-stator design enables the signal currents to pass through the capacitor without having to cross mechanical joints. Avoiding mechanical joints is critically important in this type of antenna because the high currents will cause significant voltage drops in the system and rob the available signal energy. Sometimes mechanical joints are unavoidable. Turning the shaft of the tuning capacitor will cause a large change in resonant frequency. Use a large knob or some other method of moving the capacitor shaft so that it moves only a small amount at a time. The connecting wires between the loop ends and the tuning capacitor were 5 and 6.5 inches. Altering these lengths will have a significant effect on the resonate frequency of the antenna system. The left connecting wire could have been shortened by about a couple of inches but the author chose the leave the length in place since the antenna was performing well with this extra length.

This antenna uses a gamma type matching system. The gamma capacitor (Figure 3) is mounted at the front left of the antenna base. The gamma rod is made of 3/32-inch brass rod which is bolted with a screw into the side of the capacitor mounting bracket thus making connection with one side of the capacitor. Adjusting the gamma capacitor is not as sharp as the main tuning capacitor so a smaller knob can be used. Larger knobs are useful for keeping your body from detuning the system as you make adjustments. The gamma capacitor used in this design was measured to be approximately 71.77pF.