It is important to understand that the pattern of lobes and nulls varies with each band. This information is useful for orienting the antenna and for properly anticipating performance. The precise length of the antenna between 130' and 140' will have little effect on the individual band patterns.
Changes of length will have a more profound effect upon the feedpoint impedance, as will changes of height. In contrast, changes of wire diameter between AWG #18 and #10 will have little noticeable effect.
The pages to follow are designed to allow the antenna builder to have some reasonable expectations both for antenna patterns and for impedances presented to the ATU by the antenna and its feedline. Each column in the following pages is devoted to the performance of the antenna on one of the HF bands from 80 to 10 meters. For each band there is a composite pattern plot and a pair of tables.
The patterns show NEC-2 plots of the antenna at heights of 35' and 50'. The 35' pattern is always the inner or weaker of the two patterns. If the angle of maximum radiation is greater than 45°, then the azimuth pattern is taken at an elevation angle of 45°. If the angle of maximum radiation is less than 45°, then the take-off angle is used. The elevation patterns are taken at the azimuth angle of the strongest lobe. Therefore, interpreting the patterns requires that you consider azimuth and elevation together.
The tables list, in highly rounded numbers, the impedance presented along parallel transmission lines every 20° (electrical) for a half wavelength. Standard 450-ohm (Velocity Factor = 0.95) and 300-ohm (VF = 0.80) lines are given. Note that each electrical degree represents a different length in feet and meters for each band and line type. Values are for lossless lines from the 50' high antenna.
Since impedance values repeat themselves every 180° along a feedline, you may estimate (very broadly at best) the impedance presented to your ATU. Divide the length in feet or meters of your transmission line by the length of a half-wavelength (180°) of the same line. Ignore the integer and multiply the fraction of a half wavelength by 180 to arrive at the value in degrees to check against the applicable table.
80 meters: 3.6 MHz AZ plots: Elevation angles = 45° EL plots: Azimuth angles = 90° Feedpoint Z (R ± jX): 75 + 55 ohms TL = 450 ohm; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 75 + 55 20 14.4 4.4 95 + 220 40 28.8 8.8 155 + 455 60 43.3 13.2 420 + 890 80 57.7 17.6 2450 + 770 100 72.1 22.0 680 - 1107 120 86.5 26.4 200 - 555 140 101.0 30.8 105- 280 160 115.4 35.2 80 - 100 180 129.8 39.6 75 + 55 TL = 300 ohm; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 75 + 55 20 12.1 3.7 95 + 165 40 24.3 7.4 170 + 315 60 36.4 11.1 450 + 540 80 48.6 14.8 1220 - 55 100 60.7 18.5 415 - 525 120 72.9 22.2 160 - 305 140 85.0 25.9 95 - 155 160 97.1 29.6 75 - 45 180 109.3 33.3 75 + 55
40 meters: 7.15 MHz AZ plots: El. Angle = 45° @ 35'; 39° @ 50' EL plots: Az. Angles = 90° Feedpoint Z (R ± jX): 4760 - 1270 ohms TL = 450 ohms; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 4760 - 1270 20 7.3 2.2 285 - 1085 40 14.5 4.4 90 - 500 60 21.8 6.6 50 - 245 80 29.0 8.9 40 - 70 100 36.3 11.1 40 + 90 120 43.6 13.3 55 + 270 140 50.8 15.5 100 + 550 160 58.1 17.7 365 + 1240 180 65.3 19.9 4760 - 1270 TL = 300 ohms; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 4760 - 1270 20 6.1 1.9 135 - 765 40 12.2 3.7 40 - 345 60 18.3 5.6 25 - 165 80 24.5 7.5 20 - 50 100 30.6 9.3 18.3 + 60 120 36.7 11.2 25 + 180 140 42.8 13.0 45 + 365 160 48.9 14.9 160 + 840 180 55.0 16.8 4760 - 1270
30 meters: 10.125 MHz AZ plots: El. Angle = 39° @ 35'; 27° @ 50' EL plots: Az. Angles = 90° Feedpoint Z (R ± jX): 95 - 330 ohms TL = 450 ohm; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 95 - 330 20 5.1 1.6 65 - 135 40 10.3 3.1 60 + 20 60 15.4 4.7 70 + 185 80 20.5 6.3 110 + 405 100 25.6 7.8 270 + 805 120 30.8 9.4 1805 + 1645 140 35.9 10.9 910 - 1445 160 41.0 12.5 195 - 655 180 46.1 14.1 95 - 330 TL = 300 ohms; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 95 - 330 20 4.3 1.3 55 - 165 40 8.6 2.6 40 - 45 60 13.0 4.0 40 + 55 80 17.3 5.3 55 + 175 100 21.6 6.6 100 + 350 120 25.9 7.9 330 + 730 140 30.2 9.2 2160 - 230 160 34.5 10.5 290 - 685 180 38.9 11.8 95 - 330
20 meters: 14.15 MHz AZ plots: El. Angle = 27° @ 35'; 19° @ 50' EL plots: Az. Angles = 52° @ 35' 55° @ 50' Feedpoint Z (R ± jX): 4270 - 1005 ohms TL = 450 ohm; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 4270 - 1005 20 3.8 1.1 405 - 1215 40 7.3 2.2 115 - 550 60 11.0 3.4 60 - 270 80 14.7 4.5 45 - 90 100 18.3 5.6 45 + 70 120 22.0 6.7 60 + 240 140 25.7 7.8 100 + 500 160 29.4 9.0 320 + 1070 180 33.0 10.1 4270 + 1005 TL = 300 ohm; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 4270 - 1005 20 3.1 0.9 180 - 830 40 6.2 1.9 50 - 365 60 9.3 2.8 25 - 180 80 12.4 3.8 20 - 60 100 15.5 4.7 20 + 50 120 18.5 5.7 25 + 165 140 21.6 6.6 45 + 345 160 24.7 7.5 150 + 760 180 27.8 8.5 4270 - 1005
17 meters: 18.1 MHz AZ plots: El. Angle = 19° @ 35'; 14° @ 50' EL plots: Az. Angles = 29° @ 35' 30° @ 50' Feedpoint Z (R ± jX): 125 + 5 ohms TL = 450 ohm; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 125 + 5 20 2.9 0.9 145 + 155 40 5.7 1.8 205 + 335 60 8.6 2.6 420 + 585 80 11.5 3.5 1210 + 645 100 14.3 4.4 1155 - 670 120 17.2 5.2 400 - 575 140 20.1 6.1 205 - 325 160 22.9 7.0 140 - 145 180 25.8 7.9 125 + 5 TL = 300 ohm; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 125 + 5 20 2.4 0.7 140 + 90 40 4.8 1.5 195 + 185 60 7.3 2.2 340 + 280 80 9.7 2.9 635 + 195 100 12.1 3.7 610 - 215 120 14.5 4.4 320 - 275 140 16.9 5.2 190 - 180 160 19.3 5.9 140 - 85 180 21.7 6.6 125 + 5
15 meters: 21.15 MHz AZ plots: El. Angle = 18° @ 35'; 13° @ 50' EL plots: Az. Angles = 41° @ 35' 43° @ 50' Feedpoint Z (R ± jX): 2330 + 1435 ohms TL = 450 ohms; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 2330 + 1435 20 2.5 0.8 735 - 1300 40 4.9 1.5 185 - 605 60 7.4 2.2 90 - 305 80 9.8 3.0 65 - 120 100 12.3 3.7 65 + 40 120 14.7 4.5 75 + 205 140 17.2 5.2 125 + 435 160 19.6 6.0 320 + 870 180 22.1 6.7 2330 + 1435 TL = 300 ohm; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 2330 + 1435 20 2.1 0.6 310 - 905 40 4.1 1.3 75 - 395 60 6.2 1.9 40 - 195 80 8.3 2.5 30 - 70 100 10.3 3.2 30 + 35 120 12.4 3.8 35 + 150 140 14.5 4.4 60 + 310 160 16.5 5.0 170 + 660 180 18.6 5.7 2330 + 1435
12 meters: 24.95 MHz AZ plots: El. Angle = 14° @ 35'; 10° @ 50' EL plots: Az. Angles = 23° @ 35' 24° @ 50' Feedpoint Z (R ± jX): 130 - 180 ohms TL = 450 ohm; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 130 - 180 20 2.1 0.6 110 - 25 40 4.2 1.3 120 + 130 60 6.2 1.9 170 + 305 80 8.3 2.5 325 + 565 100 10.4 3.2 1020 + 855 120 12.5 3.8 1490 - 675 140 14.6 4.4 440 - 670 160 16.6 5.1 200 - 375 180 18.7 5.7 130 - 180 TL = 300 ohm; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 130 - 180 20 1.8 0.5 100 - 70 40 3.5 1.1 95 + 25 60 5.3 1.6 110 + 125 80 7.0 2.1 170 + 250 100 8.8 2.7 370 + 410 120 10.5 3.2 920 + 205 140 12.3 3.7 575 - 440 160 14.0 4.3 230 - 320 180 15.8 4.8 130 - 180
10 meters: 28.5 MHz AZ plots: El. Angle = 13° @ 35'; 10° @ 50' EL plots: Az. Angles = 36° @ 35' 37° @ 50' Feedpoint Z (R ± jX): 2070 + 1225 ohms TL = 450 ohms; VF = .95 Deg Feet Meters R ± jX (ohms) 0 0 0 2070 + 1225 20 1.8 0.6 835 - 1230 40 3.6 1.1 215 - 605 60 5.5 1.7 105 - 310 80 7.3 2.2 75 - 120 100 9.1 2.8 70 + 35 120 10.9 3.3 85 + 200 140 12.8 3.9 135 + 420 160 14.6 4.4 345 + 825 180 16.4 5.0 2070 + 1225 TL = 300 ohms; VF = .80 Deg Feet Meters R ± jX (ohms) 0 0 0 2070 + 1225 20 1.5 0.5 360 - 895 40 3.1 0.9 90 - 395 60 4.6 1.4 45 - 195 80 6.1 1.9 35 - 70 100 7.7 2.3 30 + 35 120 9.2 2.8 40 + 145 140 10.7 3.3 65 + 305 160 12.3 3.7 190 + 640 180 13.8 4.2 2070 + 1225
Updated 7-1-97. © L. B. Cebik, W4RNL. Data may be used for personal purposes, but may not be reproduced for publication in print or any other medium without permission of the author.