The Gray-Hoverman TV antenna's plastic frame can be assembled using a jig that ensures that the antenna's components will have the correct spacing and spatial orientation. The color pdf drawing I used to build my antenna may be found at this link http://www.user.dccnet.com/jonleblanc/Canada_TV_Stations/Gray-Hoverman/DBGH_VHF_hi_Antenna.pdf. This Instructable is not a plan for building a particular antenna, but the methods I used to build mine, which attaches to a standard length of 1 1/4-inch diameter metal mast, could be applied to the many versions of the G-H antenna. It is up to the builder to determine many of the specific dimensions, which depend on the version being built and on options and personal choices. Note the license information printed on the drawing, which is offered (by others) free for private use, but commercial exploitation is prohibited.
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. That is followed by phtos of the assembly of the spine for a more recent GH10n3 antenna that has high gain for UHF and VHF-high channels.
Step 1: Envisioneering
The linked drawing of the antenna shows the size, shape and spatial orientation of the antenna's metal elements, however the design of the supporting framework is left to the builder. I chose a vertical spine of 1 1/4-inch diameter PVC water pipe. There are two horizontal tubes that run front-to-back, and their long centerlines pass through the centerlines of the straight NARODs at the front and through the centerlines of the NAROD reflectors in the back. I used two crosswise horizontal tubes to support the ends of the active elements and the NARODS. The long centerlines of these tubes pass through the centerlines of the front-to-back horizontal tubes. (These tubes are overkill for supporting straight NARODs, but I wanted a way to also support the optional "tophat" style NARODs, for experiments. See Plastic Crafts Instructables for details).
My design uses 1-inch PVC pipe fittings because the cross happens to be a snug sliding fit over 1 1/4-inch diameter standard metal tv mast. The PVC fittings are connected using lengths of 1-inch PVC pipe cut short enough that they will not hit the stops within the fittings; the jig will set the correct spacings. The antenna's metal components are attached using pieces of 1/2-inch CPVC pipe and fittings, through 0.625-inch diameter holes precisely pre-drilled through the PVC tubes and fittings. The 1/2-inch pipes can be slid to set the metal components at the correct spacings before being cemented in place during final assembly.
Step 2: How the The Assembly Jig Works
The assembly jig's base is two lengths of wood two-by-four glued into an L shape. Two small pre-drilled and pre-marked blocks are attached, one 6-inch and the other 3-inch length of two-by-four. The antenna's PVC fittings are used to set the two blocks in position for attaching onto the jig and to mark the centerlines of the tubes on the jig. I made pegs of 1/2-inch CPVC pipe that can be pushed through holes already in the plastic parts and into 0.626-inch diameter holes in the jig as the PVC parts are assembled and glued together. The exception is that a 1/4-inch bolt secures the PVC cross fitting to the jig, since a bolt will go through that hole to bind the antenna to the mast.
In the photo, the vertical peg on the right fills the hole that will accept a NAROD reflector. The PVC cross fitting is held by a metal bolt dropped into a 1/4-inch hole in the jig. Next to the cross is a PVC tee, T1, pegged in a hole that is one half inch below the centerline of the front-to-back tube of 1-inch fittings, a hole that will accept the topmost of the six primary reflector rods. Next is another PVC tee, T2, which will hold the NAROD support tubes, pegged into one of the attached wood blocks. The facing bells of T1 and T2 each have had 3/8-inch cut off them. The second attached wood block is used to position the NAROD support tubes properly in T2 before T2 is attached to the rest of the framework.
Step 3: Attach the 6-inch Block to the Jig's Base
The jig is actually constructed from left-to-right, relative to the photo, beginning with the long block, which has that 2.5-inch distance between the two holes marked on it, and the 0.625-inch dia T2 hole drilled through it. T2 is pegged into the block and its bell set 1/8-inch overlapping the edge of the jig's base. A length of 1-inch PVC pipe and a CPVC peg are used to keep T2 in the proper rotational position as the block is clamped and then attached to the jig's base with screws. The 2.5-inch mark is transferred across the jig's base using a square.
Step 4: Mark One Centerline Onto the Jig's Base
The mold marks of two PVC cross fittings connected by a short 1-inch PVC pipe can be used to mark the centerline of the 1-inch tube on the jig's base. Using that centerline, the locations of the holes in the base that will secure T1 and the cross can be marked and drilled, with the T1 hole 1/2 inch below the centerline. The mold mark on T1 is aligned with its centerline mark on the jig, then a 0.626-inch forstner bit is dropped through the fitting's hole to mark where to drill the hole in the wood. The distance between the center of that hole and the hole for the NAROD reflector rod is calculated, marked on the centerline, and drilled 0.625 diameter in the wood. All holes should be drilled a quarter inch short of going through the base.
Step 5: Mark the Second Centerline, Attach Second Block
The mold marks of two PVC cross fittings and a length of 1-inch PVC pipe are used to mark the centerline of the NAROD support tubes onto the base. The short block has the centerline of its 0.625-inch dia hole marked on it, and the hole is drilled. T2 is pegged to the short block and used to set the height for attaching the block to the jig's base, the block attaches even with the end of the base. The centerline of the T2 hole in the short block is transferred across the base using a square. A 0.625-inch hole is drilled, 1/4-inch short of going through, into the base, the distance from the short block's hole centerline and the center of the first hole in a NAROD support tube, as determined from the antenna drawing.
Step 6: Glue NAROD Support Tubes Into T2
All surfaces to be glued together are first swabbed with primer using a Q-tip, then swabbed with all-in-one cement. T2 is pegged into the short block on the jig, cement is applied to the tee and one end of a NAROD support tube which is then slid into T2 and pegged into the base of the jig. T2 is reversed and pegged into the short block again, and its second NAROD support tube is cemented into it, also pegged to the jig's base until the cement sets.
Step 7: Cement Cross, T1, T2, NAROD Reflector Support Tube
The fittings are connected using short sections of 1-inch PVC pipe cemented between them and pegged to the jig. A section of 1-inch pipe having a hole for the NAROD reflector rod is glued and pegged in place.
Step 8: Attach Spine to T1
I chose to use 1 1/4-inch PVC pipe as the spine of my antenna and modified it to connect to 1-inch T1 without using two standard adapters. A 3-inch length of 1-inch PVC pipe is cemented into T1, then T1 is pegged to the jig. The spine and 3-inch pipe are coated with cement and slid together, the spine is pegged to the jig, then two pipe clamps are tightened to squeeze the drilled and slitted end of the spine. See my Plastic Crafts Instructable.
Step 9: Make the Other End of the Frame
Repeat the steps to complete the other end of the antenna's plastic frame. Final assembly of the antenna is covered in another Instructable. The astute observer will note in the photos that the spine has only three holes for accepting the element supports, while there should be five. This was the result of an oversight during drilling of the spine tube. The hole locations had been marked and center punched, so the finished frame was taken to the drill press to drill those overlooked holes after the photos were taken.
Step 10: Antenna Information Links
1. Introduction to the Gray-Hoverman antenna
2. Antenna Research and Development Forum
3. Link to the license:
Step 11: Plastic Spine for GH10n3 Antenna
The GH10n3 antenna has high gain for UHF and VHF-high channels. Its design can be found at DigitalHome site, Antenna Research and Development heading, "Top Hat" GH with NARODs........ thread. The GH10n3 I built worked very well.