Hobbyists Create GPLed DIY Super TV Antenna 185
Freshly Exhumed writes "Retired and hobbyist antenna engineers working together in the Digital Home forums have taken an obscure 1950s UHF TV antenna called the Hoverman [PDF] and subjected the design to modern software-based computer modeling in hopes of optimizing its middling performance. The result: the new Gray-Hoverman antenna is more powerful than similar commercially manufactured consumer antennas in every category, sometimes by whopping amounts. Best thing yet: they've released the design, diagrams, and schematics under the GPLv3 so that we can roll our own! Quoth one of the testers, a former U.S. Government antenna engineer: 'Boy, this antenna is hot... This antenna is a vast, and I mean REALLY VAST improvement over anything I have used.' The home thread of the Gray-Hoverman development gives the background of their great work."
Renewed niche for broadcast TV? (Score:5, Interesting)
on that topic... (Score:3, Interesting)
I have seen various antennas capable of pulling stations from a good distance away, maybe 20 miles or more, but depending on weather and other factors they can come in pretty fuzzy. When NTSC's gone I want a solution that will work. Has anyone here played with antennas like these? I couldn't really find anything that gave the approximate range on the site.
Re:Bandwidth (Score:4, Interesting)
Re:For non DIYers (Score:-1, Interesting)
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.
For your complete copy of the GNU General Public License to go along with the designs, schematics, and diagrams, see www.gnu.org/licenses/gpl.txt
Re:Bandwidth (Score:3, Interesting)
Modeling the conventional 4-bay bowtie reflector didn't yield the kind of huge jump in performance that the Hoverman did.
Re:Renewed niche for broadcast TV? (Score:5, Interesting)
Re:The article (Score:2, Interesting)
Sorry, no pictures this time. There are just too many. By tomorrow morning the site should no longer be slashdotted.
The pictures are graphs showing this gets decent performance from about channels 14-62, with very good performance at about 34-54.
Gray-Hoverman Antenna Performance
Seeing is believing, so let's examine some of the test result diagrams of Gray-Hoverman design variants, paired with similar class commercial-brand competitors for comparison. We've chosen as benchmarks the highly regarded Channel Master 4221 4-Bay Reflector UHF Antenna and its bigger sibling, the 4228 8-Bay Reflector UHF Antenna, which is generally considered to be the best commercially made consumer antenna available for reception in North America.
As has been mentioned above, the North American spectrum of UHF Television channels will span 14 through 51 in the coming years. Thus, performance on channels above 51 was not deemed to be an important focus of our research and design resources.
Single Bay Gray-Hoverman (SBGH) vs. Channel Master 4221 4-Bay Reflector UHF Antenna:
SBGH vs. CM4221
SBGH vs. CM4221
SBGH vs. CM4221
SBGH vs. Several Commercial UHF Antennas:
SBGH vs. CM4221
DBGH vs. CM4228:
DBGH vs. CM4228
Comparative EZNEC v3 Performance Plots:
Left to Right: Original Hoverman, SBGH, CM4221
Comparative Performance Plots
Comparative EZNEC v3 Polar Plots:
Comparative Polar Plots
Comparative Polar Plots
Comparative Polar Plots
Comparative Polar Plots
Next: Get the specifications for the Gray-Hoverman Antenna
Digital Home | Digital Forum | Over-the-Air (OTA) Digital Television Discussion Forum
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Re:VHF? DTV on VHF (Score:3, Interesting)
Ugh, it's research time. As I understood it, all VHF is going away. There is some VHF DTV now so studios can get DTV stuff tested and ready for the transition. When the switch is flipped, the analog UHF stations will go away and the VHF DTV stations will move to UHF. Does anybody know for sure? Investing in VHF antenna stuff may be a waste of resources.
Does anyone know the plan? Will there be any VHF DTV after the analog switch-off?
Re:Bandwidth (Score:2, Interesting)
That the modeled hoverman looks better than the modeled conventional bowtie does not necessarily translate to the physically built antennas. This is why we still have and use antenna ranges.
Don't really need the RF bandwidth but a wifi version would be fun to build and because of the bandwidth, the tolerances won't be too severe.
30"x 40" would scale down to 8"x10" and have 14dbi(modeled) gain.
Re:The article (Score:3, Interesting)
Modelling is different tahn the old stuff. (Score:3, Interesting)
Modern model-based antenna design is a lot different and a lot more challenging. For example, building a 5-band antenna for a cell phone defies straight forward dipole etc design. People are increasingly doing very different stuff. For example, the guys over at http://www.physics.otago.ac.nz/ [otago.ac.nz] are using genetic algorithms linked with an electromagnetic modelling package to design antennas. Some of the shapes look pretty wierd.
Re:The article (Score:5, Interesting)
The models are obviously made with wire. You have some leeway on cross-section. Clothes-hangar wire might work :-) Solid copper somewhere between 12 and 18 gauge is easier to work and has the mechanical stiffness you will need.
Regarding your CB tweaking, there are a few things that can make a big change, but it is very easy to decieve yourself, too. Stereo tweakers are notorious for that.
Bruce
Re:Won't be a problem (Score:3, Interesting)
Suppose the hypothetical AntennaCorp(TM), who have tons of design and manufacturing experience, choose to implement this design in a commercial product. They build good gear, not the cheapest but the quality is second-to-none and they've got some patented manufacturing processes and parts like the design of their baluns and mounting hardware.
For obvious reasons, they want to protect their commercial properties as they give them an edge over their competitors.
What *exactly* is covered by the GPL here, and to what extent is the claimed "viral" nature of it going to affect its implementation?
It might be arguable that the protected items are the actual dimensions that define the behaviour of the device, and the actual hardware that it's implemented in/on shouldn't be covered - in much the same way that your router or your computer aren't necessarily fully open just because they run GPL software. In this case, improvements to the basic design (e.g. the discovery that changes to the dimensions improve performance) need to be given back to the community, but the way it's implemented (their super-secret balun design, their particular way of producing spacers and stand-offs etc) do not.
Or, it might be that *any* derived antenna design is covered under the GPL, meaning they need to open up all aspects of it fully. This is *not* a piece of code, it's a design for a physical object. It could end up covered under the same patent rules that affect code incorporated into GPL'd software - basically, either *don't* do that, or licence that tech for everyone to use freely in open-source products. If that was the interpretation that applied, and I owned a particular balun design that gave me an edge over my competitors, I'd be nervous about using that component in a manufactured item covered by the GPL - my competitors wouldn't be able to use the balun in closed-design antennas, but they could in anything that they chose to open the design for.
That second interpretation wouldn't be good for users or consumers, because surely the best implementation possible would be best possible outcome, and there would be impediments to AntennaCorp(TM) using the best techniques and parts.
It could all be a storm in a teacup, and I could be imagining problems that aren't there. I hope I am. Improvements to the essential electrical design of the antenna should be covered by the GPL, and it should be possible for anyone to produce an item that has the same electrical characteristics freely. Implementation details, though - the construction of the stand-offs if they're sufficiently unique and novel to earn protection, etc - *should* be able to be protected.
I like the GPL - a lot. I use a lot of GPL'd software and I've even given code and ideas back to a project (it wasn't used in that form, and was rendered unnecessary by other subsequent changes to the software that did the same thing and more, but that's not the point). But I don't want the GPL to be an impediment to these things being manufactured by the very people we would prefer making them.
Re:on that topic... (Score:3, Interesting)
Well that is only partially true.
The GPs comment of:
IS an illegal method.
On the other hand, considering how fast new programming show up on iTunes and AmazonUnbox (not mentioning Hulu yet, since it isn't "Download" per se), there ARE often legal ways to down movies and television programming.
In the past when I've had my cable go out for a day or two, once it came back, a quick trip to AmazonUnbox got the latest episode of Stargate: Atlantis downloaded straight to my TiVo. Quality wasn't as good, but It was "good enough". Yeah, it costs a few bucks each, but I've been seriously considering ditching higher tier cable in favor of this approach, especially as more of the shows I DO watch are on network TV.
The only thing holding me back is that if I ditch the higher tiers, the cable company increases the cost of my internet connection, so I'm not sure where the break-even point is (and my phone wiring is too antiquated to support DSL).