UTube 4-Bay Bowtie Antenna (without Reflector) per Maker Workshop UTube video and makezine.tv pdf file: http://www.youtube.com/watch?v=0rDPZZzIXIc and http://cachefly.oreilly.com/make/television/04/DTV_Antenna_FINAL.pdf They said to use a 3"x20" mounting board, with just over 2" Feedline Separation. Coat Hangers are cut down to 8", but extend inside feedline, so (after bend loss) are 7.5" to 7.75" whiskers. Bowtie Spacings = 5.75" and Tine Spacing = 3".
Nearly identical (earlier?) Make:TV pdf file I found via Google search is here: http://current.org/ptv/ptv0821make.pdf Note John Park points to a commercial 4-Bay Bowtie Antenna (with Reflector) and incorrectly calls it a "Hoverman". This error is repeated in both of the above pdf files.
Most popular UTube "Coat Hanger HDTV Antenna", is a 4-Bay Bowtie without Reflector (1+ Million views!!!) from babblin5: http://www.youtube.com/watch?v=EWQhlmJTMzw He says to use a 2.5"x20" mounting board, with a smaller 1.5" Feedline Separation. Coat Hangers start out as 14", so (after bend loss) are shorter 6.75" whiskers. Uses same 5.75" Bowtie Spacings and 3" Tine Spacing as above.
So "UTube TV Antenna" dimensions vary as follows: BowLength = 6.75 to 7.75-in (after bend), Bowtie Spacing = 5.75-in. Tine Separation = 3-in, Feedline Separation = 1.5 to 2.0-in, with only about 0.15-in at Crossover (wire center to wire center). Crossover is equidistant between Bowties, unlike other 4-Bays. Moving Crossover closer to the end yields better Gain and SWR.
In fol. 4nec2 simulation, a simulated SOURCE Wire feeds the antenna, with SOURCE wire radius chosen for best UHF & VHF Average Gain Test.
Poor UHF Raw Gain below 520 MHz (Ch14-21). And very poor SWR mid-band reduces Net Gain. Hi-VHF Raw Gain is constant 3.2 dBi. However VERY EXCESSIVE SWR on Ch7-13, although Ch13 isn't as bad as lower channels.
RECOMMENDATION: START OVER WITH A DIFFERENT DESIGN WITH MORE SEPARATION BETWEEN BOWTIES.
EDIT (24Aug2009): Error in 4nec2 model calculations resulted in whiskers being 1.4-in shorter than specified. New results replace old charts. Low Freq UHF Gain loss is still present, but not as severe. EXCESSIVE SWR remains a big problem.
Date(s): 27 Jan 2009. Album by holl_ands. 1 - 15 of 15 Total. 13816 Visits.
enlarge 629KB, 791x1024 1 UTube Instructions from Make:TV
Specifies 20-in x 3-in mounting board with 2-in feedline separation.
enlarge 31KB, 791x1024 2 4nec2 file for UTube 4-Bay Antenna.
Provides easy to change input data lines to investigate alternative designs.
enlarge 0KB, 739x1024 3 UTube 4-Bay with No Reflector - 3D View
Signal sucking effect of mounting board and metal mounting pipe not included in fol. charts.
enlarge 0KB, 879x1024 4 UTube 4-Bay with No Reflector - Front View
One small box = 0.5 inch
enlarge 0KB, 207x1024 5 UTube 4-Bay with No Reflector - Top View
Per UTube, at crossover, one wire lies along the mounting board, while the other hops over it with minimal separation.
enlarge 0KB, 170x1024 6 UTube 4-Bay with No Reflector - Side View
One small box = 0.5 inch
enlarge 0KB, 1024x819 7 UTube 4-Bay with No Reflector - UHF Raw Gain "As Built" Feed Separation = 2-in. Crossover wires nearly touching.
