Introduction: NAROD Bending Jig for Gray Hoverman TV Antenna
Make this jig for bending tophat NAROD elements that add VHF-high reception to the Gray-Hoverman homebuilt tv antenna. This is one of several of my Instructables related to building this antenna. To see the others and my related Instructables, click on unclesam in the INFO box at right and repeatedly click NEXT to page through them all. To receive automatic notice about my future antenna construction postings, you can click in the INFO box to subscribe to me. In the final step I include links within Digitalhome.ca that further describe the antenna.
Step 1: Materials and Tools
Board, 2X6 (actual one and one-half inches thick by five and one-half inches wide) by 32 inches long. The jig could be made on a smaller board, even a 2X4, but the larger board provides room for clamping it to a benchtop.
Wood, plywood or plastic for cleats, about one half inch thick by about one half inch wide, eight inches long
7 screws, multipurpose (drywall), one and one-quarter inches long
Wooden dowel, seven-eighths inch diameter, two pieces 2 inches long each (I cut off end of the handle from small-size toilet plunger)
Straightedge, preferably metal yardstick
Ruler or calipers divided into tenths of an inch, 2
inches or more long
Drill press (or hand drill) and seven-eights inch diameter wood bit, preferably a forstner bit.
Bit, clearance, for multipurpose screws
Wooden block for bending the wire, 2X4 four inches long or more
Clamps for holding the bender to a benchtop while bending the wire
Step 2: Draw One Horizontal
Begin by drawing a line parallel to and about one inch from one edge of the board.This jig is intended for bending #6 solid copper wire to meet the dimensions provided (by others) on this linked page http://mysite.verizon.net/imagelib/sitebuilder/misc/show_image.html?linkedwidth=actual&linkpath=http://mysite.verizon.net/res11d41p/sitebuildercontent/sitebuilderpictures/Tophat_NAROD_dim03.jpg&target=tlx_pica4bz. The drawing's dimensions refer to the centerline of the wire, and the dimensions of my bender account for the 0.162 inch diameter thickness of #6 wire, matching the drawing within a few thousandths of an inch. Other size wire can be used for the NARODs, but the dimensions of the jig would need to be adjusted. The antenna design and the dimensions on the drawing are protected (by others) by license. The information is provided free for individual use, but commercial exploitation is prohibited.
Step 3: Draw Three Vertical
Mark the center of the horizontal line. At 8.25 inches to the right of the center, draw a vertical three inches long. At 9.25 inches to the right of the center, draw another vertical three inches long. Mark the lefthand vertical at 1.64 inches above the horizontal line, then mark the other vertical at 0.60 inch above the horizontal line. These two marks are the centers of the two holes to be drilled.
Step 4: Drill Then Draw Some More
Drill a seven eighths-inch diameter hole at the marks on the two vertical lines. At the top edge of the lower hole, draw a horizontal line to the left for six inches long. At the top edge of the upper hole, draw a horizontal line to the left for six inches long. At the top edge of the upper hole, draw a horizontal line to the right for six inches long.
Step 5: Cut and Attach Cleats
Cut one cleat seven inches long and attach it with one edge right on the horizontal line, about a half inch past the righthand vertical line. Cut the short cleat three-quarters of an inch long and attach it with one edge against the lefthand vertical line and its head end against the horizontal line that runs left from the top of the lower hole. Mark the short cleat so it can be removed and re-installed in the same orientation every time.
Step 6: Let Us Bend
Prepare a length of #6 bare copper wire by straightening it (see my Instructable Straightening Heavy Solid Copper Wire). File one end square and file off burrs. Measure and mark 34.532 inches length from that end. Cut the wire a little long, file it to the correct length and remove burrs. Install only the lower wooden dowel and remove the small cleat from the bender. Carefully measure and mark the center of the wire, at 17.266 inches. Install the wire on the bender with the wire's center mark on the bender's center mark. Clamp the wire so it cannot be pulled off the center by the bending. Clamp the bender to a benchtop in several places. Use a wooden block to press the wire against the peg as the wire is bent, until the wire aligns with the six-inch horizontal lines.
Step 7: Prepare for the Second Bend
Add the short cleat and the second peg to the bender.
Step 8: Make the Second Bend
Use the block to wrap the wire closely around the second peg until it aligns with the six-inch horizontal line. (Disregard the fact that the pegs appear to have been swapped in the photo sequence, the photos are from two different bendings).
Step 9: Bend the Other End
Remove the small cleat and the pegs and the wire from the bender. Place the other end of the wire in the bender and clamp the wire so its midpoint will remain on the midpoint of the horizontal line. Repeat the bending process. When the wire is again removed from the bender, the loops may need to be very gently bent or twisted a little to make the loops fall in the same plane. Don't play with it too much.
Step 10: Antenna Information Links
1. The Gray-Hoverman version I am making is described at this link, though tophat NARODs may offer improved VHF-high reception over the straight ones: http://www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdf
2. Introduction to the Gray-Hoverman antenna
3. Antenna Research and Development Forum
4. Photo of mast-mounted outdoor G-H antenna (by others, post #94), having tophat NARODs
5. The antenna design information is protected by license (by others), is made available free for individual use, but commercial exploitation is prohibited. Link to the license:
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