Slashdot Mirror
Hobbyists Create GPLed DIY Super TV Antenna
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."
The main reason the original Hoverman died out was that the bandwidth was not enough to cover the UHF (Ch 14-83) spectrum. This new variant appears to mainly improve on it by shifting its limited bandwidth down. The difference nowadays is that with the 700 and 800 Mhz bands removed from the spectrum used for TV, the basic Hoverman design DOES have the bandwidth to cover it, at least starting next year for "in-core" channels in the US.
They are auctioning off the frequencies used by 18 UTF channels, leaving 38. Most HDTV programming is delivered by UTF.
Performance and Designs, Schematics, and Diagrams to follow as they become available.
Gray-Hoverman Antenna | Performance | Designs, Schematics, And Diagrams | Join the Digital Forum Discussion
The Gray-Hoverman Antenna For UHF Television Reception
March 13, 2008
This project is dedicated to Doyt R. Hoverman (b.1913), the man who created and did the early work on the Hoverman antenna at a time when antenna modeling programs did not exist. His work would have been entirely created and improved by field testing, trial and error, and with a great amount of calculation without the benefit of electronic devices. Without his efforts, our work would not have been. Doyt Hoverman passed away in December, 1989 at Van Wert, Ohio, USA.
First, A Bit About The Original Hoverman Antenna
Doyt R. Hoverman's original design for a television antenna was granted US patents #2918672 on 22 Dec 1959 and #3148371 on 8 Sept 1964, which expired in 1979 and 1984 respectively. To view them, click on this link and then simply enter the patent number mentioned above to retrieve each.
In his patent applications, Hoverman describes two designs with 4 rod reflectors, full wavelength and co-linear half-wavelength reflectors, with the second design using the following specifications:
* Driven array = 56" dual segments with 8 subsections of 7" (same as the first design)
* Reflector spacing = 3.5"
* Full Wavelength Reflectors:
o Top and bottom = 29"
o The two middle = 24"
* Half Wavelength Co-Linear Reflectors
o Top and bottom = 14"
o The two middle = 10"
The above dimensions are for reception of UHF channels ranging from 14 to 35, as claimed in the patent. He gives design equations for shifting the range, and suggests 35-58 and 58-83, although the range 58-83 is not applicable now as UHF TV channels in North America only go to 69, and after 2009 will only go to 51.
The original Hoverman antenna design did not have a reflector and used a driven array of 56" segments with eight zig-zag 7" sub-elements. The original patent # 2918672 claimed UHF and VHF reception. The modeling results did not find any positive net gain for VHF Low channels 2-6 nor for VHF High channels 7-13.
There is very little information available anywhere on the Hoverman antenna. The only reference to any commercially manufactured Hoverman antennas seems to be in the article (PDF) The Hoverman, VUD Sept 1982, which mentioned a 4 bay Hoverman made by AntennaCraft named the model G-1483 and which was also made for Radio Shack as the model 15-1627, seen in this photo courtesy of tvlurker:
Radio Shack Hoverman
Some of these commercially manufactured Hoverman variants used 7 pairs of collinear rod reflectors. Judging from the AntennaCraft and Radio Shack websites and many Internet searches those Hoverman models do not seem to be currently in manufacture, although it seems that old stock of the AntennaCraft Super-G 1483 is or was available from SummitSource.com.
Recent Research On The Hoverman
Canadian antenna buff Autofils, speculating in an online discussion of Build It Yourself Antennas on the Digital Home web site in early 2008 on the possibility of experimenting with the old Hoverman Antenna design, sought out old sparks, another Canadian antenna enthusiast, who used 4NEC2 computer antenna modelling software to model the original Hoverman design. His research showed that the Hoverman had p
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
Even if someone does begin marketing these commercially, I don't see "cheap knock-offs" being a problem. It doesn't cost anything more to manufacture one of these with the correct dimensions (which is pretty much what determines its performance) than to make one with the wrong dimensions. The only thing that would likely make an antenna "cheap" in this sense is purely mechanical - inability to hold up in high winds, or to the sun's UV (I've seen some TV antennas with plastic components that were literally crumbling due to long-term UV exposure).
Check out this antenna: http://uhfhdtvantenna.blogspot.com/
It has gotten some interesting write ups and looks similar in many ways to the new hoverman.
Actually it's 37 UHF channels, because channel 37 is reserved for radio astronomy. And 2-13 are still available, but 2-6 are not very good for ATSC. So that leaves 44-49 channels.
However, unlike NTSC, ATSC tolerates broadcasting on adjacent channels (other than the gaps at 4-5, 6-7, and 13-14), and is more tolerant of distant stations on the same channel, so it uses the spectrum more efficiently. In the past, you could have no more than 35 channels in any given market, and now you can have at least 40.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
Oops, I forgot about the "UHF taboo" limitations of channels n+14 and n+15 (and sometimes n-7), due to the way UHF tuners usually do IF. Apparently those are still a problem with ATSC, but less so than with NTSC.
#naabhaprzrag, #sverubfr-000, #agi-fcbafberq, negvpyr[pynff*=' negvpyr-ary-'] { qvfcynl: abar !vzcbegnag; }
There are a number of stations broadcasting in VHF DTV presently, and there will be quite a few more post-Feb09 transition. Several VHF stations will retake their VHF frequency for DTV. The biggest reason to go to VHF is that it needs substantially less power to cover a certain number of square miles.
Very few stations, though, will be in the low-VHF ranges (channels 2-6). Ignition noise, lightning, etc, are big problems in low-VHF. Those frequencies covered a lot of ground for the watt, even with more interference in that band. But, the errors are generally too much for digital reception, so there aren't but a dozen or so low-VHF digital transmitters now. I expect that 30 MHz will eventually be repurposed.
But, high-VHF (RF channels 7-13) is probably with us for quite a while.
The ARRL Antenna Manual is probably one of the longest-standing references for antenna and feedline theory.
+++OK ATH