This jig makes it easy to form the zigzag active elements needed for every version of the Gray-Hoverman tv antenna, using prepared links of common quarter-inch diameter copper tubing. The time and effort needed to make the jig will pay off in the quality and consistency of the elements produced, and the jig can be used many times if friends or neighbors also want to build their own antennas. My method produces elements that are durable, lightweight, have the desirable sharp corners and have holes for mounting the elements to the antenna's framework. This is one of three Instructables about making the active elements. To see the other two and my related Instructables, click on unclesam in the INFO box to the right, then repeatedly click NEXT to page through them all. To receive automatic notice when I post future Instuctables about my method for assembling the entire outdoor antenna, members can click to subscribe to me.
Step 1: Materials and Tools
Base: particle board or plywood, flat, 12 inches by 32 inches, one half to three quarters of an inch thick; edges do not need to be perfectly straight or smooth, nor the corners perfectly square.
Screw Posts: nine 6-32 screws, one and one-half inches long; twenty-seven 6-32 nuts; eighteen number six flat washers.
Drawing paper 12 inches by 32 inches (Optional) You can also draw directly on the base board, but paper will allow greater precision.
Drawing compass(es), having hard, very sharp pencil lead or dividers having very sharp points; capable of drawing arcs up to 7.07 inches (180 mm) radius, such as Dasco Pro, Inc., Giant Circle 12-inch Beam Compass shown in photo.
Pencil having hard, very fine point
Straight edge, such as yardstick, metal version preferred
Ruler, one foot long, divided into tenths of an inch or in millimeters
Drill bit nine sixty-fourths (0.140) inches diameter; another bit about half that diameter for pilot holes
Screwdriver, for 6-32 screw head
Wrenches, two, for 6-32 nut
Medium-width permanent marker
Step 2: Layout
Care in the drawing is essential to making quality antenna elements and in facilitating their construction. It is more important that each of the arcs intended to have the same radius do have the same radius, than that the radii are perfectly the radius specified. DO NOT DRAW DOTS AT THE LINE INTERSECTIONS. The intersections need to be located with as much precision as possible, and the drilling of the holes needs to be done with great care.
The design of the Gray-Hoverman antenna and its dimensions are protected under license (by others). This information is offered free for personal use, but no commercial exploitation is permitted. This is a link to the color pdf drawing of the antenna that I used for the active element dimensions http://www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdf. In the final step I provide links within the digitalhome.ca website that provide history, description, performance, variations, and construction examples of the antenna, as well as to the license.
Step 3: Draw Six Five-Inch (127 Mm) Arcs
1. Draw a straight horizontal line no farther than one inch from the lower edge of the board or paper, it need not be perfectly parallel with the edge of the board or paper.
2. Draw a straight vertical line perfectly perpendicular to the base line and no farther than one inch from the left edge of the board or paper.
3. Adjust the compass to 5.00 inches (127 mm) and, working from the left intersection, mark off six equal spaces along the base line, as shown in the photo. Do not draw dots.
4. Draw a straight vertical line perfectly perpendicular with the base line, at the intersection of the sixth arc.
5. Check the perpendicularity of the two vertical lines by confirming that they are 30.00 inches apart at their top ends.
Step 4: Draw Six 7.07-Inch (180 Mm) Arcs
Adjust the compass to 7.07 inches (180 mm) and make arcs from only those intersections on the baseline indicated in the photo. Do not draw dots at the intersections.
Step 5: Draw Two 5.41-Inch (137 Mm) Arcs
1. Adjust the compass to 5.41 inches (137 mm), set its point at the intersections of the two vertical lines and two of the 7.07-inch arcs, and draw an arc near the end of each vertical line. The photo defines the nine points at which holes will be drilled for the screw posts, but do not draw dots. Note that the distance between the screw posts will be identical to the dimensions provided on the antenna drawing, except for the screw posts at the bitter ends of the two short stubs. The copper element stub links will be the same length as specified on the antenna drawing, but the screw posts for the stubs are intentionally 0.18 inch closer together.
2. If drawing on paper, tape the paper to the base board and transfer the nine points to the board by poking through with a very fine sharp pin. It is OK to draw a light open circle, at least a quarter inch in diameter, around each of the pin points in the board to make it easier to locate them when drilling.
Step 6: Punch and Drill
1. Carefully make an extremely small center punch mark at each of the 9 points on the board.
2. Drill a pilot hole through the board at one point, using a bit about half the diameter of the nine sixty-fourths (0.140) inch diameter bit, as an aid to centering the drill press in each punch mark.
3. Without moving the board, switch to the nine sixty-fourths (0.140) inch diameter bit and carefully drill through that pilot hole.
4. Repeat to drill the remaining eight holes.
Step 7: Screw It
1. Draw ink lines linking the holes to make it easier to visualize assembly of the antenna elements.
2. Insert a screw in each hole, with a washer on each side of the board, and snug on a nut at the base of each screw post.
3. Add two more nuts to each screw post, adjust the upper nut so its top edge is one quarter of an inch from the top of its post.
4. Hold the upper nut and tighten the lower nut against it to jam it in place, ensure the quarter inch spacing. These two nuts will never need to be removed.
Step 8: Label the Links
Mark letters beside each link as shown. Add a small U or L near the ends of each link, as a reminder which link will be the upper and which will be the lower at each screw post during final assembly. It is easiest to place the links onto the jig by first placing all the lower links, then adding the upper links, reverse the order when removing them.
Step 9: G-H Antenna Information Links
1. Introduction to the Gray-Hoverman antenna
2. Antenna Research and Development Forum
3. Photo of mast-mounted outdoor G-H antenna (by others, post #94)
4. License governing the use of the antenna design information