David Macnaughton and his Fascinating World of Amateur Radio

ANTENNA DIMENSIONS AND POLAR DIAGRAMS

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Return to:   28.5MHz, 5 Element Yagi Used until mid April, 2000 Design centre frequency:  28.50 MHz Element Lengths: Total length of each element is indicated. Sorry, I have used decimal feet for the imperial dimensions of the elements and spacings. The element diameter is 19mm (0.75"), Boom diameter is 32mm (1 1/4") Reflector:  5.322M (17.460'), Driven element:   4.918M (16.032'), Director 1:  4.870M (15.980'), Director 2:  4.760M (15.614'), Director 3:   4.536M (14.884') Element Spacings from reflector: Driven element: 0.911M ( 2.989'), Director 1: 1.822M (5.978'), Director 2: 4.328M (14.198'),  Director 3: 7.137M (23.415' )         Fig 1 - 28.5Mhz, 5El yagi in free space   Return to:   29MHz, 6 Element Yagi Used after Mid April, 2000 Design centre frequency:  29.0 MHz Notes: This antenna started out as a Bill Orr design for a 6 El yagi, from the book Beam Antenna Handbook 5th edition. The design was then computer enhanced using Y0 V6.5. I used a Trombone 1/2 wave line to transform the coax impedance of 50 ohms to 200 ohms and then a "T" match without series capacitors to match the array. For some reason not determined, the array was hard to match at 29MHz, best results for VSWR being obtained at 29.3MHz. The dipole was lengthened by 50mm (2") at each end during test and the test results were much better. It has been left in that state. The design presented below is the original design from the computer, before the dipole length change during test. Element Lengths: Total length of each element is indicated. Sorry, I have used decimal feet for the imperial dimensions of the elements and spacings. The element diameter is 19mm (0.75"), Boom diameter is 32mm (1 1/4") Reflector:  5.134M (16.846'), Driven element:   4.782M (16.022'), Director 1:  4.590M (15.06'), Director 2:  4.539M (14.894'), Director 3:   4.489M (14.728'), Director 4:   4.439M (14.562') Element Spacings from reflector: Driven element:  1.589M ( 5.213'), Director 1:  3.178M (10.426'), Director 2:  4.767M (15.639'), Director 3:  6.356M (20.853' ), Director 4:  7.945M (26.066' ) Fig 2 - 29Mhz, 6El yagi in free space       50MHz, 7El Yagi on 40' Boom Design centre frequency:  50.110 MHz Element Lengths: Total length of each element is indicated. Sorry, I have used decimal feet for the imperial dimensions of the elements and spacings. Element Diameter is 16mm (0.63"), boom diameter is 32mm (1 1/4") Reflector:  2.908M (9.542'), Driven element:   2.628M (8.624'), Director 1:  2.692M (8.832') Director 2:  2.638M (8.654'), Director 3:   2.608M (8.556'), Director 4: 2.614M (8.574') Director 5:  2.658M (8.724') Element Spacings from reflector: Driven element: 1.410M (4.626'), Director 1: 2.967M (9.736'), Director 2: 5.164M (16.943), Director 3: 7.566M (24.822'), Director 4: 10.043M (32.949'), Director 5: 11.960M (39.239')    Fig 2:  50.11Mhz, 7El yagi in free space NOTE I have endeavoured to provide the above dimensions and figures free of error, and I am passing them on with good will in an attempt to help home constructors.  I suggest that you check the designs on your own computer modelling programme before attempting a large construction project. I would be very happy to receive any advice of errors located on this page. Thank you. This information is provided in good faith, and I accept no responsibility for any problems that you may find.    Return to: