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UHF Bi-Quad NO Refl - khaye
UHF Bi-Quad with NO Reflector (per khaye post) analyzed using 4nec2.

Element Diameter = 1/8-inch (AWG8), All Diamond Sides = 17 cm (6.7-in), Feedpoint Gap Size = 2 cm (0.78-in) [4nec2 model used 0.75-in]
Outer Angles = 45.0-deg, Inner Angles = 54.5-deg (would be 45-deg for zero Gap Size).  [AWG10 would slightly degrade SWR.]

Not quite optimum for New UHF Band (Ch14-51), with high SWR on Ch14.  Improve by using about 10-percent longer side lengths: 18.7-cm (7.4-in).

Optimum size for Old UHF Band (Ch14-69) would be 16.3-cm (6.4-in) per side, shifting indicated performance at 770 up to 806 MHz.
Date(s): 13 Mar 2011. Album by holl_ands. 1 - 12 of 12 Total. 8607 Visits.
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UHF Bi-Quad, 17-cm/side, NO Reflector
3D View


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UHF Bi-Quad, 17-cm/side, NO Reflector
Front View
[1 small box = 1 centimeter]


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UHF Bi-Quad, 17-cm/side, NO Reflector
Side View
[1 small box = 1 centimeter]


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UHF Bi-Quad, 17-cm/side, NO Reflector
UHF Raw Gain ~ 5.6 to 7.5 dBi


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UHF Bi-Quad, 17-cm/side, NO Reflector
UHF SWR (300-ohms) Under 5.5


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UHF Bi-Quad, 17-cm/side, NO Reflector
UHF Impedance


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UHF Bi-Quad, 17-cm/side, NO Reflector
Azimuthal Pattern at 470 MHz


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UHF Bi-Quad, 17-cm/side, NO Reflector
Azimuthal Pattern at 590 MHz


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UHF Bi-Quad, 17-cm/side, NO Reflector
Azimuthal Pattern at 698 MHz


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UHF Bi-Quad, 17-cm/side, NO Reflector
Azimuthal Pattern at 806 MHz


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DOC11
UHF Bi-Quad, 17-cm/side, NO Reflector
4nec2 File


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UHF Bi-Quad, 17-cm/side, NO Reflector
Top View
[1 small box = 0.5 centimeter]


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Try an unequal biquad. 32/37cm (13"x15") seems to work well for me on both UHF and VHF-hi.
 - 
Tom Street, Sat, 25 Feb 2012 1:21PM