This is how I prepare quarter-inch outside diameter copper tubing links that form the zigzag active elements for a Gray-Hoverman tv antenna. This is one of three Instructables that describe my method for producing consistent, quality elements that are lightweight, durable, have the desirable sharp corners and have holes for mounting the elements to the antenna's framework. To see the other two, one how to build the needed assembly jig, one detailing the final element assembly, and my other 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 in the INFO box.
Step 1: Tools and Materials
copper tubing, one quarter-inch outside diameter, five feet long for each zigzag (includes plenty for cutting waste). Two zigzags required for each antenna, two required for each bay of a multibay antenna). Choose thickwall or thinwall, as discussed below
Gray Hoverman TV Antenna Assembly Jig, subject of another Instructable
Tubing cutter, wheel type for the thickwall tubing or tiny hacksaw for thinwall
Tubing flaring tool, or something similar, for gripping tubing without damage while cutting it
Combination pliers, large
Scribe or scratch awl, metal, sharp
Flat plank for rolling links straight
Ruler, one foot, divided into tenths of an inch
Dividers or beam compass capable of transferring measurements up to 8 inches
Flat files, coarse to fine
Rattail file, round, that will fit into end of tubing for deburring cut ends
Electric drill or drill press, and bit nine sixty-fourths (0.140) inch diameter, plus bit about half that diameter for pilot hole
Needle file, round, that will fit inside a hole 0.140 diameter
Tape, masking or painter's
Medium point permanent marker
Step 2: Choose Copper Tubing
Quarter-inch outside diameter copper tubing is commonly sold (as well as two larger diameters) retail, priced by the foot, cut from a large coil in the store. This has a shiny surface and reddish color. A version having a thinner wall is also sold as a ten-foot length coiled in its own box. The thinwall has a satin gold or brass exterior appearance (photo) and looks very gold on its inside. The thinnest-wall version is marked "Utility Coil," and the lightest, cheapest version of those is marked "hecho en Mexico" on its box. Either is suitable for making the antenna active elements, but the thinwall Mexican is much easier to work with. Zigzags I made from the heavier tubing averaged 153 grams (5.4 oz) each, while the thinwall zigzags weighed 113 grams (4 oz) (I was not parsimonious with the solder). The thinwall is easier to form and solder, but is less strong. Either can hold insulated brackets for supporting a NAROD on an indoor antenna, by the two holes in each of the short antenna stubs. However, an outdoor antenna should provide mechanical support for the active elements at all points, including by the holes at the bitter ends of the short stubs, regardless of whether thick or thinwall tubing is used.
Step 3: Mark Eight Links to Length
The design of the Gray-Hoverman antenna and its dimensions are protected by license (by others). This information is offered free for personal use, but commercial exploitation is prohibited. This is a link to the color pfd drawing I used for the dimensions of these components http://www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdf
. The final step has links to the antenna design and the license.
1. Carefully measure and mark each link for cutting, making every effort to get the lengths correct. It may be necessary to cut each length a little long then deburr and trim to its correct length by filing. It is not necessary that the links start life perfectly straight, they will be straightened later. However, before each link is measured and cut off, straighten the next section of tubing by pressing it with your palm against a flat surface, to remove the more obvious curves.
Step 4: Cut and Deburr the Links
As you cut and deburr the links, put same-length ones together in a marked bin or bundle them so you won't have to worry about getting them mixed up. Thickwall tubing may be cut using a plumber's wheeled pipe cutter (wheel nice and sharp), but the thinwall will be crushed by it. The thinwall is best cut with a tiny hacksaw, and either method works best if the tubing is held gently in a tubing flaring tool which is itself chucked in a vise. Links cut with a saw need to be cut long enough to allow for plenty of deburring and filing to proper final length. Tubing cut with a pipe cutter will need to be cut a little long as well, since the wheel does push some material out of its way. The wheel cutter works best if a narrow groove is made with a tiny flat file (gun file) or knife, just past the link's length mark, for the wheel to start in. Advance practice with some marked scrap peices is worth the effort. It is possible to estimate the place to cut using the wheel and not need to file the link to length. In that case, I do not deburr the inside of the ends. I just flatten the ends as in the following steps then file off whatever sticks out past the intended length of the link, at both ends.
Step 5: Roll Me Over
Before proceeding further, it is important to straighten the links. Each is rolled in turn between a sturdy flat hard plank against a flat hard surface until it is straight. The thinwall straightens very easily, the thickwall requires application of more pressure and time. Pressure should be applied only when the link is moving, otherwise it could be accidently distored. A crooked link will rumble while it is being rolled, and the rumbling will stop when it has become straight for the thinwall and straight-ish for the thickwall.
Step 6: Crunch-O Smash-O Smalltime
1. Use pliers to partially flatten one end of every link to a length of about 0.40 inches, and both ends of the middle four of them. Make sure, by eye, that the flat to be formed on the second end will line up with the existing one.
2. Thoroughly flatten those pads in a vise. As you flatten, sight from above and straighten up the link, front to back, so the plane of the pad in the vise lines up with the long axis of the link. Press only on the part of the link closest to the vise jaws.
3. After flattening a pad on the second end of a link, sight from the top pad and if it does not line up with the one in the vise (with the vise jaws) grasp it with pliers and gently rotate it into proper orientation. These same alignment checks should be done once all the following steps have been performed and before the links are placed on the assembly jig the final time for soldering.
4. Lightly file off sharp edges and corners at the ends of the pads.
Step 7: Crunch-O Smash-O Bigtime
1. Make a mark on the top of links A-B-G-H 0.70 inch from their unflattened ends.
2. Use pliers to partially flatten the end of the link, at a forty-five degree angle through the mark. By eye, ensure that the new flat will align rotationally with the one at its other end.
3. Use the vise to completely flatten the larger pads at a forty-five degree angle across the link, also correcting each for bending and rotational alignment.
4. No need to file away sharp edges and points at the ends of the large pads at this time, they will be cut off later.
Step 8: Tape Tab Each Link
The links will not be interchangeable, and it is also important that they are kept in proper rotational position during some following operations. Attach and mark a folded tab of tape, in a way that it will not be difficult to remove later, to the middle of each link. Each tab should stick out to the right side, with its letter readable when the link is in its eventual position on the assembly jig. This is particularly important for A, B, G and H. Note that the U and L letters help you quickly figure out which face of each pad will need to be cleaned and tinned and for the correct assembly on the jig for final soldering.
Step 9: Mark Pads for Punching
1. Measure and scribe a centerline on every pad, the same face of the two pads on each link, typically 0.18 inch from one edge.
2. On only one small pad on each link, mark the centerline of each of those pads at a distance of 0.18 inch from the end of the link.
3. Make a very small centerpunch dimple on those small pads at each marked spot. Do not drill.
Step 10: Mark and Punch Second Hole Location
1. Carefully take the actual measure between the centers of the screw posts (it's the same as inside edge of one post to outside edge of the other) for each particular link, in turn, using dividers or compass. The distance will probably not be exactly the same even for similar links.
2. Mark the centerline of the remaining pad, that actual distance, from the punch mark, at the other end of each link, with the dividers or compass.
3. Make a small center punch mark on those remaining unpunched pads.
Step 11: Drill the Link Pads
1. Drill a small pilot hole at each punch mark, then drill through with a nine sixty-fourths (0.140) diameter drill.
2. Thoroughly file off the burrs around each hole on both sides of the pads.
3. Try each link at its designated position on the assembly jig and use a needle file as needed to get each to drop snugly onto both its screw posts.
Step 12: Trim the Large Pads
1. Place the A-B and G-H corners onto the assembly jig with the links in their proper orientations.
2. Scribe a line for cutting off the excess of each long pad.
3. Cut at each line with tin snips and file for a good fit without overlap.
4. Lightly file off sharp edges and slightly round over the sharp points. The links are ready for final assembly, described in another Instructable.