A Scrap T.V. Becomes an OTA Antenna

Like a Phoenix rising from the ashes, this build enabled me to convert a recovered asset into a valuable piece of high performance hardware that allowed me to cut the cable umbilical cord, with a substantial savings of monthly payments. I finally got tired of shelling out for cable T.V. with it's reruns, infomercials, programs in languages I cannot speak, and channels I will never watch. Being a child of the '50's and '60's, time traveling back to watching over the air broadcasts held no terror for me and frankly, I was looking forward to doing it again. With the change to digital transmission now solidly in place, it remained simply to do a little research into my particular needs then enjoy the savings, and this is how I did it.

Hot surfaces may be encountered during this build, work gloves are advised. Common tools and machinery may also be used, safety procedures particular to them should also be observed.

I'm situated about 50 miles (81km) southeast of most T.V. transmitters beaming down from Orlando Florida across very flat terrain. I have a concrete/ stucco home construction which means I live in a wire mesh steel box, and on the ground floor too so adequate indoor reception was going to be highly questionable. As I'm only using an inside style, I constructed an adjustable antenna farm trying out the various designs that are most popular, and at what position. The result was that a tiltable solid bow-tie version with a reflector gave me the best signal strength over the whole UHF spectrum, in all the rooms of my home, and for most of the time. Success meant that I now had 5 systems to build: 3 for me, 2 for my son.

I had planned all along to use material I recovered as described in my Instrucatable: Asset Recovery II: Plasma TV Harvest, and fashioned a somewhat crude proof of design build with scrap bits, and was delighted to find that a double- bay prototype easily managed to pull in the most stations while also displaying several very stable signal strength bars. This design was based on the excellent work done by By Dave Muse, AKA; apeweek, a cardboard/ foil build complete with 1:1 patterns. Now I'm ready for production.

There's usually a bit more to setting up an indoor antenna than just plug and play, especially if you're on the far edges of the transmission band. Since getting ahold of a reliable signal may take some experimenting with placement I found it easiest to use a tripod as it can adjust for height as well as the horizontal and vertical plumb antenna positions. All three factors may need to be explored before finding that sweet spot where reception is peak on all channels. You can then design a base or support system with confidence. Some locations allowed for the simplest of stands, others required a more inspired solution.

I made a template so I could rough cut out my sections including extras, from the main chassis plate which was .060” [1.52 mm] thick using a jig saw. I refined them by using a simple holding fixture and trimming to final dimensions on my radial arm saw. A toothed non abrasive metal cutting blade gave accurate, uniform workpieces. A single mounting hole was drilled at the nose, which was also useful in the next step.

The remains of the glued on foam membrane used in the manufacture of the plasma TV chassis needed to be removed, the simplest method was to heat the work and scrape off the residue. This went rapidly and was not at all unpleasant to do using my shop toaster oven, a scrap board, and a paint scraper. I heated a batch for about 15 minutes, removed one from the oven with pliers and gloves, and placed it on the board. A brad sunk slightly below the surface of the elements nose hole kept them in place while being squeegeed off, yielding a nearly mill- finish surface. A quick final cleaning with kerosene (paraffin oil) and a steel wool ball finished this step.

Looking rather scratchy from the previous original salvage process, I decided to give them a textured finish to visually enhance them since I'd be looking at them for many years. I used a wire wheel mounted in an angle grinder, and set to stropping the worst side, so as to have a decent obverse one without the need of further attention to it. A screw through the nose held the work to scrap wood which was clamped to the bench, and with a little practice a pretty decent pattern emerged that I deemed satisfactory for my purposes, all that was left then was to bend up the wings.

The final treatment to the elements was to introduce two 45 degree wings using a simple shop-made bender or “brake”. I made this more or less a permanent tool since I'll undoubtedly have more light metalworking projects in the future, but it worked a treat for this one. I oftentimes find diverging from the main project to be refreshing when building adjunct projects, it allows some time to reflect on what has been accomplished and what needs be done next, so I have no regrets about the time spent thus, it was not wasted. Step1 was to form a 45° angle on one edge, using a cereal box cardboard template as a gauge. Step2 was to form the other 45° angle for an included total of 90°. Spring-back did happen, but easily became predictable after a few bends, so the total batch went pretty quickly.

The back shells saved from the Plasma TV harvest now became the source for this application, even looking the part with it's numerous ventilation holes which not only lightened them, but seemed somehow fitting. In no way was performance compromised by the perforations since even a wire oven rack would work for this purpose, it's just that these looked sexier I think.

Simple half- lap & glued joints were used to form the wooden fork mountings that spaced the element assemblies away from the reflectors at the recommended distance. Plastic tabs fashioned from scrapped cutting boards were used to isolate and attach the element assembly, as wood can sometimes conduct and dampen radio frequency energy causing possible signal loss. Where appropriate, signal leads were routed to a tie point for the Baluns to mount.

In my case I found there was indeed a difference in Balun performance. A Balun is an impedance matching circuit that optimizes the signal transfer from the antenna to the 75 ohm television input. I used an assortment of these purchased at various thrift stores and found that some performed better than others, yielding up a few more signal strength bars and stations. Some antenna enthusiasts state they have had good results by doing a direct hookup and not using a Balun. This may work when a strong signal is present, but I have found it lacking in my location. The cable from the antenna to my set is kept as short as possible, and is an RG6 designation with a solid copper center conductor giving the lowest voltage drop; since this is all about delivering the maximum signal voltage to the tuner, even the little things can collectively have a large influence. I ended up buying a threaded Balun set as described below, and was very happy with the improved performance over the push- on styles.

Adding an amplifier introduces a whole new dynamic to the project, and was not needed in my case. The majority opinion seems to be if it's not an absolute necessity, you're better off not employing one as it can introduce it's own set of problems. Planning and execution of this project took place over a span of months, but resulted in a lot of empirical knowledge about how best to convert from a paying service to a free one, I doubt now I'll ever go back.

• The original antenna design referred to in the above Instructable, complete with printable patterns and build discussion.

http://apeweek.hubpages.com/hub/make-this-powerful-hdtv-antenna-out-of-cardboard

By Dave Muse, AKA; apeweek

• RG6 cable source, variable lengths available:

http://www.amazon.com/gp/product/B00IQKY0AM/ref=as_li_tl?ie=UTF8&camp=1789&creative=390957&creativeASIN=B00IQKY0AM&linkCode=as2&tag=laliho-20&linkId=7YOTL34ASTJR44CZ

• Broadcast station finders:

http://www.antennapoint.com/

http://disablemycable.com/station_finder.php

• Baluns (transformers), a 6- pack that met my needs:

http://www.ebay.com/itm/6-UHF-VHF-TV-FM-Coaxial-Matching-Transformer-75-300-/120763412108?pt=US_Audio_Cables_Adapters&hash=item1c1e0f6e8c

• Majority of parts for this project were obtained from:

https://www.instructables.com/id/Asset-Recovery-II-Plasma-TV-Harvest/