A new design for a UHF VHF/Hi antenna that really rocks has just been released under the GNU General Public License. The forum home page is at http://www.digitalhome.ca/ and the thread with the plans is at http://www.digitalhome.ca/forum/showthread.php?t=99907. The page with the plans can be found here: http://www.digitalhome.ca/forum/showthread.php?t=99907&page=7 The links to the plans are in the second post from the top, #92.
The design is called the Double Bay Grey-Hoverman UHF/VHF hi with NARODs. A NAROD, according to the inventor, is Not A Reflector Or Director. The NARODs flatten the frequency response of the antenna, and allow it to develop appreciable gain in the upper VHF band. With the lower VHF band going away, that is all that is needed for the future of over the air television reception. Another advantage of this particular design is that it has appreciable gain on the back side as well. It looks to me to be the ideal antenna design for my particular needs.
While not a stranger to the idea of building my own TV antenna, I had always used improvised methods that got me a signal I could live with. I had often contemplated building a better antenna, but thought the design of such a thing beyond my level of knowledge.
Most everyone at one time or another has wrapped aluminum foil around the ends of the "rabbit ears", or stuck a potato on there to improve reception. I have done that a time or two, with mixed results. My first "homemade antenna" of any worth was a length of 300Ω twinlead split about 30" and the ends tacked to the wall with thumbtacks. This served me well during the time I stayed at the farm, about eight years.
After I started staying here at the shop, I had a couple of commercial antennas. The first was used, and the second I bought new at Radio Shack. After the Radio Shack antenna got knocked down and damaged beyond repair, I made a dipole out of coat hangers nailed to a block of wood, which can be seen in Figure 1. This has worked well enough for my limited TV viewing for the past decade.
When the change to digital television came in February 2009, one station that had a couple of shows I liked to watch quit broadcasting in analog. The TV I have now is the first, and only TV I ever bought. Before that I used patched together junkers. I could have gotten a converter box, but have gotten used to watching movies etc. on the computer with much better picture quality. I do not watch enough TV to justify the cost of a new HD unit, so I looked into getting a HD tuner card for my computer. I run a Debian GNU/Linux distribution, so I needed a card that had drivers for Linux. I chose the HD-5500 from http://pchdtv.com/ because it is specifically designed for the Linux OS. I got the card, installed it, and nothing. So I went looking at antenna information on the web and found a Youtube video of a guy making an antenna from coat hangers. I made one following his directions, but using #12 AWG bare copper wire instead. Still nothing. So I put it up on the roof. That made an incredible difference in analog reception, but still nothing on the HD-5500. I started looking around on the web some more, and found the forum at http://www.digitalhome.ca/. I started to read, and followed a link somewhere which launched Kaffeine player. I killed the link, I do not like the Kaffeine plugin, but when I closed the browser Kaffeine was on the screen and had the Digital Television button enabled. So I clicked it. It said "no mri". Go figure. So I looked at the menu under DVB and it had an item labeled "channels", and on that dialog "scan", so I clicked that and 24 channels loaded. Wow. It works. But Kaffeine is a bit buggy, and the picture had some pixelation, was jerky, and the sound cut out on some channels. I installed MythTV, but it was no better. Signal strength was just not up to snuff. I just needed a better antenna.
You can see the Youtube antenna I built from the back, Figure 2, and the business end, Figure 3. While a better build of this design with a reflector in back etc. may well have given enough signal for most of the channels, there are still some that would be left out.
Figure 4 is the TV Fool data for this location. From this you can see that I need either two antennas, or one that is capable of reception in both directions. Enter the Double Bay Grey-Hoverman UHF/VHF-hi with NARODs. I had been reading the threads on the different builds of the Grey-Hoverman design, and this particular build looked ideal for my situation. So when the plans were posted on March 8th 2009, I started looking at what I had lying around that I could use for such a project. I was no longer worried that I was too ignorant to do something like that because all the hard work had already been done by others. All I had to do was follow the plans and build the thing.
These are the old antennas I found in the junk pile. The one seen in Figures 5, 6, 7, & 8 is the used one that I referred to earlier. It was given to me by a friend. I had just bought the TV and the supplied "rabbit ear" style antenna just was not enough. I told my friend that I guessed I was going to have to buy an antenna, and he told me he had one that he had just replaced because it had been damaged when a limb fell on it during a wind storm. He said it was a real good antenna, and that I could have it if I thought I could fix it. So I replaced the broken elements with 3/8" hard copper tubing, straightened the bent ones the best I could, and put it up. It was a pain to use though, because it was very directional and needed to be on a rotator. I had mounted it on a piece of steel tubing which was going up through a hole in the ridge cap on the roof. I had a handle on the tubing so I could aim the antenna from inside the attic. This was fine, but meant running up the stairs and moving the antenna every time I changed the channel. I got tired of that very soon, and went to Radio Shack and bought the smallest, cheapest outdoor antenna they had. I put it up in place of the big one, and it worked out better. I rarely needed to go into the attic to change direction. This lasted a while, then I moved into the building next door while I was remodeling the offices in this building. I moved the antenna over, mounted on the back wall of the building, above a shed roof. I had removed a board on the gable end near the antenna so I could adjust it from inside the attic. After finding a good compromise direction, I replaced the board. A burglar came, climbed up on the shed roof, and pulled the board off to gain access to the attic, and then the building. In the process the antenna got knocked down and was severely damaged. This is the antenna shown in Figure 9.
From these antennas I was able to salvage enough aluminum tubing to make the reflectors for the Gray-Hoverman. Also the hard copper tubing which I could use for the NARODs and NAROD reflectors. A bonus was that the Large antenna had the boom in good shape, I would use that to make the mast for the DBGH antenna. There were 14 insulated element holders which I could use to hold the reflectors. I needed 12. Two are shown in Figure 10.
I had a piece of GPO3 (electrical grade fiberglass, Figure 11) that I had bought several years ago for a project at work. It was not delivered in time, so I had to improvise something else. The 12" square by 1/4" thick piece had been sitting around gathering dust ever since. I had some #10AWG solid wire on hand, Some Plexiglass, and misc. hardware.
I purchased 25' of #6AWG bare copper wire for the driven elements, three fiberglass electric fence posts from Tractor Supply, a 10' length of 1/2" CPVC plumbing pipe for spacers, a cheap balun, a RG6 grounding block, some antenna mounting "U" bolts from Radio Shack, and a 3/8" steel wire brush to clean the inside of the reflector rods. That I thought, should be every thing I needed.
I was able to get enough aluminum tubing from the two junk antenna's elements to make all the reflectors I needed. I cut the tubing into lengths just a little longer than the finished reflectors were supposed to be. I used the factory crimped ends wherever possible, and when I got to cutting the longer tubes so my pieces had open ends, I crimped one end of each piece by squeezing it in a vice, then grinding to a contour that matched the ends of the elements from the Radio Shack antenna. The other antenna had a different style of crimp, and I do not have the technology to reproduce that. Then using the bench grinder, I ground the reflector rods down to their final length, then deburred the ground ends.
As the old insulators I would be using to hold the reflectors were designed to hold a single rod passing through, and I was going to have two rods spaced evenly in the middle, I needed some sort of spacer/connector. I cut 12 pieces of the fiberglass electric fence post 3 13/16" long. Then using the lathe, I turned 1 1/2" of each end down from 3/8" O.D. to 5/16" O.D.. This turned down part would fit into the open ends of the reflectors. The part in the middle that was still 3/8 O.D. would act as a spacer. I made sure the finished length of the spacer part was 0.79" as per the plan.
In Figure 12 you can see some of the cut fiberglass rods that have not been to the lathe yet in the lower left corner. In the middle of the picture are two of the turned down rods. Above that shows two reflector rods connected by the spacer rod, and at the top is a reflector holder with the assembly installed. I used a 3/8" steel wire brush to clean the inside of the reflectors where they fit over the spacer rod. A little dab of epoxy will hold them in place nicely.
By the way, the tape measure is not part of the antenna. It is just there to weight the green cloth because the wind was getting a little gusty when the picture was taken.
The boom from the larger of the salvaged antennas was 99" long. I calculated the required length of my boom to be 66" center to center from the top and bottom mounting holes for the NARODs (from the plans) plus a couple of inches extra on top and bottom for good measure to make 70" for the antenna. I added 18" for mounting making a total of 88" for the boom. So I cut off 11" from the original 99". Figure 13 shows the cut, however the saw cut through so fast I was unable to get the camera in position before the extra material had been cut off and hit the floor. You can just see an end of the extra piece in the lower right hand corner of the picture.
I cut four pieces each 1 1/2" long from the extra piece. These would be used to make "ears" for the mounting hardware to attach to when mounting the boom to the mast. Figure 14 shows the extra pieces arranged as they would be positioned, and the bottom two clamped in place for welding. To the left you can see in the middle of the pile of reflector rods and remnants of the original elements they were cut from, a bubble pack with the two "U" bolt clamps that will pass through holes drilled in these "ears" for them.
Next the "ears" were welded on. I used some ER4043 0.035" aluminum wire in the wire feed welder, with pure argon shielding gas. The welds were ground smooth so the mounting hardware could lie flat. A view of the boom leaning against a dolly showing the finished and ground welds is Figure 15.
The holes for the stand-offs for the mounting blocks for the driven elements, NARODs, and NAROD reflectors were marked out according to the center to center dimensions for those elements on the plan, then drilled using a 3/8" drill bit. The boom was then sanded and acid etched using PPG DX533 metal cleaner in preparation for paint.
The insulating blocks for mounting the elements were made from the piece of GPO3 shown earlier in Figure 11. As this piece was 12' X 12" and I needed six pieces long and wide enough to securely mount the corners of the zig-zag elements, as well as eight pieces suitable for mounting the NARODs and their reflectors, carefull consideration was called for. Since I would be cutting this on a table saw, and the kerf of the blade is 1/8", I would loose 1/8" with each cut. After much head scratching, tape measuring, pencil scribbling, and calculator punching, I came up with these dimensions that would work. Driven element blocks: 5 15/16" X 2 3/4". NAROD and NAROD reflector blocks: 5 5/16" X 3/4".
I took the piece of GPO3 next door to a building (which is used primarily for storage) where the table saw is, only to find the table saw was equipped with a masonry blade. The fine tooth carbide tipped blade for finish cuts in plywood, most often recommended for this type of work, was hanging on the wall behind a large pile of commercial light fixtures I had saved from the dumpster a couple of years ago. Only by levitation, or moving that pile of fixtures would get me access to the proper blade. So i thought I would give the masonry blade a try, just to see what happened. It worked. It worked better than any plywood blade. It made a very smooth cut with no need of sanding afterward. So I made all the cuts using the masonry blade and am very happy with the result shown in Figure 16.
Now each of the fourteen pieces would need a 5/16" hole in the center tapped 3/8-16 for the fiberglass rods used to hold the blocks in place. Also 1/2" CPVC plumbing pipe would be used for spacing the blocks away from the boom, and the inside diameter was a bit larger than the 3/8" fiberglass rods, so some way of keeping the CPVC spacers centered would be needed. I looked in the drill bit drawer to see what I could find, but nothing seemed to be the right size. The CPVC pipe is just a hair over 5/8" O.D., so a 5/8" spade bit was too narrow, a regular drill bit would cut a pointed hole leaving no room for threads, a 3/4" spade bit was too wide, it would not hold the pipe centered any better than the 3/8" fiberglass rod. I found a worn out 3/4" spade bit and took it to the bench grinder. after carefully removing enough material from each side of the bit to get it the right size for the pipe, I carefully resharpened it. You can see this bit starting to make its cut 1/16" deep into the first of the mounting blocks in Figure 17.
After all the blocks had the centering depression cut into them, they made another round to receive the 5/16" pilot hole for the 3/8-16 threads Figure 18. The result is shown in Figure 19.
Figure 20 shows the start of the alignment pin holes, and Figure 21 shows the finished alignment pin and pilot holes for the screws used to secure the clamping blocks. All these holes were drilled with a #7 drill bit to receive 1/4-2 threads. Figure 22 shows the 1/8" deep depression cut with a 1/2" end mill to provide clearance for the bend in the driven element. Figure 23 shows the clearance depression cut to accommodate the phasing lines. This was done on the two blocks which were to be used for the center positions of each bay.
Some grooves were cut into the six mounting blocks for the driven elements with a 1/8" end mill. The grooves were cut 1/8" deep and 0.153" wide for the #6AWG wire that was used to make the driven elements. Yes I know that #6AWG is supposed to be 0.162" diameter, but I measured the stuff I bought at the hardware store with a micrometer, and it measured 0.154". I made the grooves 0.001" narrow so they would provide a friction fit for the wire. I thought this might make assembly a bit easier, but I was wrong. If I had it to do over I would just make the grooves the same width as the wire. The finished blocks can be seen in Figure 24 with the grooves cut, and the holes tapped. The block on the bottom left is flipped over to the back side so you can see the centering depression for the CPVC spacer.
The eight blocks for mounting the NARODs and NAROD reflectors had the center holes done the same way. The outer holes were drilled with a #29 drill bit and tapped 8-32. These can be seen in their finished form in Figure 25.
This should have been the easiest part of the job, or so I thought, but again I was wrong. I cut four pieces of fiberglass rod to length for the NAROD and NAROD reflector stand-offs, and six pieces for the driven element blocks. I cut these parts on the lathe using a hacksaw, and was able to get very nice square smooth cuts and precise lengths using this method. I used the same method to cut the six spacers for the driven elements, four spacers for the front side of the NAROD holder assemblies, and four spacers for the back side of the NAROD holder assemblies. All this went without a hitch.
The next part was to put 3/8-16 threads on the ends of the rods. This is where I ran into trouble. I had purchased a new die for the job, not wanting to use my good adjustable die as fiberglass is quite abrasive. It did not work. It just chewed up the fiberglass. I ended up using the adjustable die anyway. This worked O.K. for the short threads where the rods went into the fiberglass blocks, it just took about four passes tightening the die 1/2 turn on each adjusting screw each pass. However on the longer threads on the back side of the pieces used for the driven element blocks, where the rod passed through the boom and was to be fastened with a nut, the last pass always ate the threads. I did not want to go to town and buy another fiberglass fence post, so I just turned the ruined threaded parts down to 5/16" and threaded them with the 5/16-18 adjustable die. It cut easily, and in only two passes. I take it the 3/8 die must have already been dulled, probably by threading some copper rod a while back. Anyway, you can see the results in Figure 26.
Figure 27 shows some pre-assembly work. The rods were screwed into their respective blocks after coating the threads with epoxy cement. Then the spacers were glued into their centering depressions with epoxy.
I made a bending jig as suggested in the thread at http://www.digitalhome.ca/forum/showthread.php?t=95898 (post #9) from an old piece of plywood that had been used for a "shelf" for the back seat of a car. The car was long gone and the "shelf" had been in storage for a couple of decades. It was the right size already, so I thought I would put it to good use. I laid out the center lines of the zig-zag element according to the plan, calculated the position of the nails based on the outer diameter of the wire, and pre-drilled holes just slightly smaller than the O.D. of the nails so I could insert or remove the nails by hand at will. The jig is seen in Figure 28.
While this jig proved helpfull for measuring and marking, it did not work out well for bending. I am renaming it my "measuring and marking jig". I tried bending using a pair of linemans pliers to hold the wire on one side and a piece of aluminum tubing with an inside diameter slightly larger than the wire to pull it around the nail, but the result was always too large of a radius. I needed nice sharp bends to fit my support blocks, and to maintain the dimensional accuracy of the plan. So I found another way to bend my wire. I put the wire in a vice with the top edge of a Sharpie mark even with the top edge of the vice jaws Figure 29 and slid the aluminum tube down to the vice, Figure 30, then pulled the aluminum tube down to make the bend, Figure 31, finishing off by "massaging" the wire around the corner with a 4oz ballpeen hammer, Figure 32. This produced the nice sharp 90 degree bends I needed. In Figure 33 you can see the bent wire being compared to a draftsman's triangle to verify the angle.
The next step is to place the wire which has its first bend in the center back on the measuring and marking jig so that it can be marked for the next two bends, Figure 34. Now in order to maintain the dimensional accuracy it is very critical where the mark is placed on the wire. Note that on my measuring and marking jig the black lines represent the position of the center of the wire. The nails are positioned in back, or to the inside of the radius of the bend. In order for the center of the bend to end up in the right spot, the mark is aligned with the centerline of the nail, with the marker held parallel with the line that is to be the center line of the wire after it is bent. This is demonstrated in Figure 35.
The wire is taken back to the vice, and the same bending procedure outlined above applied to each bend. Here I might mention that one of the main reasons given for the bending jig in the first place is to ensure that all the bends are made in the same plane, and you don't end up with some sort of free-form three dimensional sculpture. I was able to work around this problem by setting the vice so that the jaws just overhung the edge of the cast iron table top so the wire could hang straight down from the vice where it was clamped. The edge of the table top made an easy place to align the wire vertically, and the edge of the tabletop made a place to align the previously bent section of wire with. Now all I had to do was to sight down the wire and the edge of the table and bend the nest segment in a straight line with that. I didn't have any problem with getting my bends out of alignment, no free-form 3-D thing going on here.
After making the second set of bends, it is back to the measurement and marking jig to get set for the next two bends as in Figure 36. Then back to the vice where the bending process is repeated for each of the next two bends, then back to the jig for the next marks, and back to the jig for the next bends. Once these last two bends are completed, they are just bent 45 degrees, you end up with the final setting on the measurement and marking jig to mark the ends of the wires for cutting to length. Here the measurement is taken from the center of the center line of the outer bends of the zig-zag element which is the black line running the length of the jig just below the row of four nails in Figure 37. The wire is marked where it is to be cut, and the cut made with linemans pliers, right on the mark. Figure 38 is a closeup of the wire cut to length.
This entire process is repeated for each of the four zig-zag driven elements. Actually after figuring out how to go about the procedure, and making the first element, it proved to be quite easy, went quickly, and was so much fun I wanted do do more. The newly bent elements looked so good, wicked really, quite a different form from the previously innocuous looking straight wire.
Most folks who build these things, I take it, use screws to clamp the driven element down to the phasing lines. Perhaps some use solder. I feel that a strictly mechanical connection may not prove to be reliable over time, as exposure to the natural elements will produce corrosion sooner or later. And I have not had much luck with soldered connections, using regular 60/40 rosin core solder when it is exposed to weather either. Given a choice between the two, I think the mechanical connection would prove to be the most reliable. There is another choice available, though, that is to solder with silver solder like used to solder copper fittings used in air conditioning and refrigeration technology. This stuff lasts for years when exposed to weather, is mechanically very strong, and has excellent electrical conductivity to boot. I decided that I would use silver solder to make the connections between the driven elements and the phasing lines. But to get a good solder joint requires a good mechanical connection first, so I set about thinking how to go about such a thing.
The requirements are that the joint must be physically strong, must allow easy adjustment for the position of the phasing line so that the phasing lines can be the right distance apart and centered between the driven elements, and must be portable so that the silver soldering can be done somewhere other than on the antenna itself. The way I came up with was to drill holes through the driven element at the contact points so that the thinner wire of the phasing lines could pass through. This would satisfy all of the requirements, and should not be too hard to do.
First I put the center bend of the zig-zag element in the vice with just tip of the bend where the contact point was to be sticking out, Figure 39. Then with a small flat file, filed the tip flat so that it could be center-punched, Figure 40. Then using a very sharp center punch, two pairs of glasses (my vision "just ain't what it usta bee"), and my trusty 4oz ballpeen hammer, punched a center mark into the copper wire where the hole was to be drilled, Figure 41. Then using a #38 drill bit, which is just a bit larger than a #10 AWG bare solid copper wire, drilled the through hole in the center of the bend, Figure 42. It is important to drill very slowly, as copper is soft, and will not drill well at high speed. It is also helpful to use a suitable lubricant when drilling such soft metal, such as condensed milk. A close-up of a finished hole is shown in Figure 43. Figure 44 shows a test piece of #10 AWG copper wire stuck into the finished hole to test the fit.
The finished zig-zag driven elements are now set aside to wait for the assembly of the framework, and the phasing lines. On with the next part.
Firstly, the wire the phasing lines are made from needs to be straight. So does the wire the driven elements are made from, for that matter. There are some methods that are commonly given for straightening wire. One is to put one end of the wire in a vise, and the other end in a drill, and use the drill to twist the wire. I have never used that method, and have my doubts about it as well, such as I think it might "work harden" the wire. Another method you will see mentioned from time to time is to put one end of the wire in a vice, hold the other end with vice grip pliers, and hit the vice grip pliers with a hammer while pulling in the wire with the vice grip pliers. That does work for smaller wire, and is similar to the method I use.
The way I straighten wire is to tie the wire between an immovable object and a vehicle of some sort, and give it a yank. That is how I straightened the wire for this project, both the #6 AWG for the driven elements, and the #10 AWG for the phase lines. I used an old motor home chassis (with all four wheels chocked) that is waiting to be cut up for scrap as the immovable object, and "the beast", my 1977 GMC 3/4 ton pickup truck as the prime mover. In Figure 45 you can see the #10 wire tied to the motor home chassis, and in Figure 46 you can see the wire tied to "the beast". If you look closely in both of these pictures, you can see the remnants of the #6 AWG that was previously straightened by this process.
In the case of the #6 AWG, the procedure is to leave a few feet of slack in the wire between the trucks. Then start the engine, and with the engine running at a fast idle, put the transmission in drive, let the truck take off forward until BOOM the wire stops the truck dead in its tracks. Then all you have to do is put the truck in park, cut the wire loose, and drag it away to be measured and cut into lengths for its intended purpose.
The #10 AWG is not so robust, and requires a little gentler treatment. You don't need as much slack, and use a normal idle speed on the engine. It may be necessary to give a little gas at first, just enough to get the truck to start to roll, then let the idle speed of the engine do the work. There is no loud boom, either, the truck just stops moving. Yank too hard and the wire will break. That may do O.K., or the snapping of the wire may result in it getting kinked up again. Your milage may vary. I like it better to have the wire stay tied on to both vehicles, as it makes stripping the wire so much easier. I leave the motor idling and the gearshift in drive to maintain tension on the wire for the stripping part. I suppose I should mention at this point, for the benefit of any safety Nazis who might read this, that I had a helper standing by behind the wheel so in case the wire broke or came loose, he could stop the truck. I would not want the truck to take off by itself and run across the street into my neighbors house! If you look closely in Figure 47, you can just make out the wire being held in tension by this method. It helps if you can zoom in. With the wire so tensioned, it is very easy to strip, just walk along it with a utility knife, and peel of a slice of insulation. the rest of the insulation zips off in one piece. Figure 48 shows me stripping the wire this way.
Now this story might seem to get a little out of order. Oh well. Figure 49 shows the framework assembled and with its first coat of primer, but that is necessary for the phasing lines to be marked and bent. Anyway, on with the story of the phasing lines.
First two pieces of the straightened #10 AWG wire were cut longer than necessary. Then tabs were silver soldered to these wires in the center of their length. The tabs were formed from .030" thick copper sheet. The copper sheet was rolled around a #39 drill bit, just a little smaller than a 310 AWG wire, for about 2/3 of the circumference so that it could "snap" over the wire and have a friction fit. Then the tab was bent at a right angle to the rolled part. Holes suitable for #6 screws were punched into the tabs, then they were silver soldered on. In Figure 50 you can see the tabs on the wires as they lay on the supporting framework between the driven elements which have been temporarily fitted in their grooves. The phasing line wires were centered top to bottom and marks made where the first bends were to be made, Figure 51. These first bends were made just using linemans pliers and fingers, then the second set of bends made so that the center to center distance between first and second bends was 1" as per the plans. Figure 52 shows he ends of one of the wires inserted into the hole in the center of the driven element at the feed point. Now it was possible to measure and adjust these wires so that the two phasing lines would be exactly centered between the driven elements, and exactly 2" apart center to center. The wires were marked using a razor blade for a scribe, the excess cut off so none stuck out the other side of the hole, and the assemblies taken outside to be silver soldered. After soldering these assemblies were put into a protected storage area while they waited for the rest of the antenna to be finished up to the point that it was ready for them.
Now I have to back track just a little bit. Figure 53 shows the first stage in the assembly of the supporting frame structure. The boom, which has been drilled and prepaired for painting at this stage, is shown sitting on the pre-fabricated NAROD support blocks and stand-offs last seen in Figure 27. Figure 54 shows the first of the NAROD / NAROD reflector stand off assemblies finished. Epoxy was mixed and applied to the as yet unglued end of the spacer on the pre-fabricated part, then to both ends of the remaining spacer tube, then to the threads on the end of the fiberglass rod where it screws into the fiberglass support block. Note the straight edge and speed square used to assure perfect alignment of the lower block, a carpenters square was employed to assure alignment of both front and back blocks. This procedure was repeated four times. You may have noticed that I have found a use for those AOL and MSN CDs they used to send in the mail all the time back in the "browser war" days, as well as the occasional "coaster" created when user error or software malfunction causes a CD to fail the burning process. As a palette to mix epoxy on.
The next step was to install the driven element support blocks.As these have also been pre-assembled, all that is necessary is to put a little epoxy on the unglued end of the spacer, stick the rod through the hole, run up the nut, align and tighten. Figure 55 shows this stage completed.
Three coats of white sandable primer N.A.P.A. part no. DAP 1689, were then applied, followed by a coat of DA 1605 flat black acrylic enamel to seal the primer and also to make the antenna look a bit less obtrusive. Of course there was the little detour after the first coat, the trial assembly of the driven elements in order to measure the phasing lines for bending and cutting. Also you may have noticed the Plexiglas clamps on the floor in some of the pictures, Figures 51 and 56, these were left off for the first prime coat, but installed with their nylon screws for the second and third prime coats, and the finishing topcoat. I am hoping that the paint will help to protect these plastic parts from the harsh Texas sun. By the way, Figure 57 is after the painting is done, and the support structure is ready for the final assembly, that is the installation of the elements.
Next comes the installation of the reflector holders. Four of these will require some modification. A hole was cut with a 3/4" hole saw centered 2 1/2" away from the center of the reflector rod, then the other end cut off through the center of the hole. These modified reflector holders will be placed on either side of each center stand-off as seen in Figure 58. The reflector holders were then secured to the boom with 8-32 machine screws and nuts. After all the reflector holders were mounted, the reflector rods were installed using epoxy to secure them to their spacer rods. A picture of the finished reflector installation is Figure 59.
The whole thing is flipped over and the NAROD reflectors are installed next, Figure 60. I won't go into the details of removing the corrosion from these things, but I will tell you it was a pain. The 3/8" O.D. hard copper tubing was in the stock when my father bought out a failed hardware store back during World War II. He stored it in the barn at the farm then, in fear it would be confiscated by the Government for use in the war effort. It was forgotten about and stayed there until the barn was torn down in 1980. Then it was moved here to the shop and some was stored in the attic, while some was stored on the metal rack outside. So needless to say, there was a great patina on there, all green and everything. I did clean that all off, though, because the Ohm meter indicated that it was not conductive, and I believe that such a coating may have had a negative effect on the tubing's electrical properties considering the application.
Figure 61 shows the antenna front side up again, and the NARODs themselves installed. Now in the plans it shows the NARODs to be made of #10 AWG copper wire, and in the forum, they say it is O.K. to use #6 AWG, or #4 AWG, or even 1/4" rod or tubing. I used this stuff because it is what I had, and because it is hard copper tubing, it will not bend, even if a bird decides to sit upon it.
In Figure 62 you can see the almost completed antenna. The driven elements including the phasing lines have been installed, and the driven element ends spaced away from the NARODs with Lexan spacers specially fabricated for the purpose. The phasing lines have been spaced with some Lexan spacers as well.
Figure 63 is a close-up showing the phasing lines spaced with Lexan spacers, and the balun attached to the tabs on the phasing lines with 6-32 brass machine screws and nuts. These connection points were sealed with "Carlon multi-purpose Weather Guard spray-on rubber film" part no. VC9WG5. A six foot "pigtail" of RG6 coaxial cable was attached to the balun with a rubber weather boot filled with silicon dielectric compound. This "pigtail" was attached to the boom using UV rated tie-wraps. The other end of the "pigtail" will be attached to the grounding block when the antenna is mounted, again using the weather boot and silicon dielectric compound.
Figure 64 is another close-up, this time of the Lexan spacers used for the NAROD to driven element ends spacing. The antenna did seem to be just a bit wobbly, but adding these spacers really stiffened it up.
Well folks, that is all for now. All that is left is to take this thing up onto the roof, mount it, and see what happens. Wish me luck!
Before the antenna could be installed, I had to do some tree trimming. There were some limbs that had grown out and down and were blocking my access to the roof where the ladder fits. The limbs needed to be cut anyway, because they would sometimes make quite a racket rubbing on the roof when the wind was blowing hard. But they had to be cut out of the way to get the antenna onto the roof without snagging it, and possibly damaging it. So I spent half a day cutting limbs and carrying them off to the burn pile.
There are no pictures of the actual installation process, as I had my hands full with the antenna itself, and trying not to slip on the slick roof. It is not that step, about 30 degrees, but there is new tin, all shiny and slick. Here is a picture of the antenna installed.
I've had a week to play with this thing now, and must say I am impressed. Rock solid on all the desired front side channels, and very good on most of the back side channels. Here is a list of analog stations I am getting with this antenna. Some of them vary with time of day, and weather etc., but the list is fairly representitive of the reception over all. If you click on the channel number you can see a snapshot of what I see with XawTV. The quality ratings in the table below are subjective, but based on reception with an actual analog television set, so if they do not match what you see in the snapshots, that is why.
|2||KCWX||CW||Fredricksburg||poor||not watchable can tell it is CW|
|4||WOAI||NBC||San Antonio||poor||watchable has some snow, much herringbone|
|5||KENS||CBS||San Antonio||poor||watchable has some snow, much herringbone|
|9||KLRN||PBS||San Antonio||very good|
|11||KQUX||Austin||fair||occasional white lines, speckles|
|17||KNIC||fair||reflective interference (multi-path)|
|18||KLRU||PBS||Austin||excellent||will stop broadcasting analog April 16 2009|
|20||KADF||Austin||very good||low power station|
|31||KHPG||UNI||Giddings||fair||watchable snow same as 17, identifies self as channel 62 is a repeater|
|32||KGBS||MTV||Austin||fair||watchable snow low power station|
|34||K34FM||TBN||Austin||poor||watchable snow also KTBN|
|51||KBVO||CW||Austin||excellent||repeater for KNVA|
And here is a list of the digital stations. I kept watch on the maps at http://www.dxinfocentre.com/tropo.html so as to be fairly sure that the results represented in these tables are not under the influence of Tropospheric Ducting.Top
|Virtual Channel||Real Channel||Station ID||Network||SNR||Signal Strength||Comments|
|4-2||58||MX||8||75||For some reason no snapshot|
|12-3||48||KSATSD2||10||75||This one is a blank screen|
|16-1||16||KHCE||TBN||6||53||These are shown by TVfool to be virtual 23|
|16-2||16||Church||7||52||I have listed them as Kaffene found them|
|60-1||38||KVDA-DT||TEL||6||50||For some reason no snapshot|
|62-2||36||KTFO-CA||8||72||For some reason no snapshot|
The Gray-Hoverman antenna designs, schematics, and diagrams on this site are Copyright ©2008, 2009 and are free: you can redistribute them and/or modify them under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at our option) any later version.
These designs, schematics, and diagrams are distributed in the hope that they will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
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