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332 lines
13 KiB
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<meta name="keywords" content="Doublet, Dipole, HF Lower, HF Upper">
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<title>A 135' Center-Fed Multi-band Dipole Data Compendium</title>
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<h1><img src="../images/yagicad.gif" align="left" width="125" height="62" border="2" vspace="5" hspace="10">ANTENNAS FROM THE GROUND UP<img src="../images/w4rnlwwr.gif" align="right" width="99" height="83" border="2" vspace="5" hspace="10"></h1>
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<h3>5. 8-to-1 Odds<br>
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or a 135' Center-Fed Multi-band Dipole Data Compendium</h3>
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</center>
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<center>
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<h3>L. B. Cebik, W4RNL</h3>
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</center><br>
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<br>
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<img src="../images/colorbar.gif" align="middle" width="540" height="4">
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</center><br>
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<br>
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The most popular multiband wire antenna is the 80-meter dipole fed with parallel transmission line and an antenna tuning unit (ATU). It goes under many names. Likewise, it has many recommended lengths. We shall somewhat arbitrarily use 135' as our length. The models will assume #14 copper wire over average earth. Figure 1 illustrates the antenna.
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<center>
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<img src="gup5-1.gif" width="431" height="190" border="2" vspace="5" hspace="9">
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</center>
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<p>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.</p>
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<p>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.</p>
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<p>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.</p>
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<p>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.</p>
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<p>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.</p>
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<p>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.</p>
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<center>
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<img src="gup5-2.gif" width="638" height="764" border="2" vspace="5" hspace="9">
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</center>
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<pre>80 meters: 3.6 MHz
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AZ plots: Elevation angles = 45°
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EL plots: Azimuth angles = 90°
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Feedpoint Z (R ± jX): 75 + 55 ohms
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TL = 450 ohm; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 75 + 55
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20 14.4 4.4 95 + 220
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40 28.8 8.8 155 + 455
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60 43.3 13.2 420 + 890
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80 57.7 17.6 2450 + 770
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100 72.1 22.0 680 - 1107
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120 86.5 26.4 200 - 555
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140 101.0 30.8 105- 280
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160 115.4 35.2 80 - 100
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180 129.8 39.6 75 + 55
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TL = 300 ohm; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 75 + 55
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20 12.1 3.7 95 + 165
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40 24.3 7.4 170 + 315
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60 36.4 11.1 450 + 540
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80 48.6 14.8 1220 - 55
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100 60.7 18.5 415 - 525
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120 72.9 22.2 160 - 305
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140 85.0 25.9 95 - 155
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160 97.1 29.6 75 - 45
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180 109.3 33.3 75 + 55</pre>
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<center>
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<img src="gup5-3.gif" width="638" height="766" border="2" vspace="5" hspace="9">
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</center>
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<pre>40 meters: 7.15 MHz
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AZ plots: El. Angle = 45° @ 35';
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39° @ 50'
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EL plots: Az. Angles = 90°
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Feedpoint Z (R ± jX): 4760 - 1270 ohms
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TL = 450 ohms; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 4760 - 1270
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20 7.3 2.2 285 - 1085
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40 14.5 4.4 90 - 500
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60 21.8 6.6 50 - 245
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80 29.0 8.9 40 - 70
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100 36.3 11.1 40 + 90
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120 43.6 13.3 55 + 270
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140 50.8 15.5 100 + 550
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160 58.1 17.7 365 + 1240
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180 65.3 19.9 4760 - 1270
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TL = 300 ohms; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 4760 - 1270
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20 6.1 1.9 135 - 765
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40 12.2 3.7 40 - 345
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60 18.3 5.6 25 - 165
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80 24.5 7.5 20 - 50
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100 30.6 9.3 18.3 + 60
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120 36.7 11.2 25 + 180
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140 42.8 13.0 45 + 365
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160 48.9 14.9 160 + 840
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180 55.0 16.8 4760 - 1270</pre>
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<center>
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<img src="gup5-4.gif" width="636" height="758" border="2" vspace="5" hspace="9">
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</center>
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<pre>30 meters: 10.125 MHz
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AZ plots: El. Angle = 39° @ 35';
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27° @ 50'
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EL plots: Az. Angles = 90°
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Feedpoint Z (R ± jX): 95 - 330 ohms
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TL = 450 ohm; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 95 - 330
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20 5.1 1.6 65 - 135
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40 10.3 3.1 60 + 20
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60 15.4 4.7 70 + 185
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80 20.5 6.3 110 + 405
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100 25.6 7.8 270 + 805
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120 30.8 9.4 1805 + 1645
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140 35.9 10.9 910 - 1445
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160 41.0 12.5 195 - 655
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180 46.1 14.1 95 - 330
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TL = 300 ohms; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 95 - 330
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20 4.3 1.3 55 - 165
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40 8.6 2.6 40 - 45
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60 13.0 4.0 40 + 55
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80 17.3 5.3 55 + 175
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100 21.6 6.6 100 + 350
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120 25.9 7.9 330 + 730
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140 30.2 9.2 2160 - 230
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160 34.5 10.5 290 - 685
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180 38.9 11.8 95 - 330</pre>
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<center>
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<img src="gup5-5.gif" width="636" height="760" border="2" vspace="5" hspace="9">
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</center>
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<pre>20 meters: 14.15 MHz
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AZ plots: El. Angle = 27° @ 35';
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19° @ 50'
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EL plots: Az. Angles = 52° @ 35'
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55° @ 50'
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Feedpoint Z (R ± jX): 4270 - 1005 ohms
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TL = 450 ohm; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 4270 - 1005
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20 3.8 1.1 405 - 1215
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40 7.3 2.2 115 - 550
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60 11.0 3.4 60 - 270
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80 14.7 4.5 45 - 90
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100 18.3 5.6 45 + 70
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120 22.0 6.7 60 + 240
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140 25.7 7.8 100 + 500
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160 29.4 9.0 320 + 1070
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180 33.0 10.1 4270 + 1005
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TL = 300 ohm; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 4270 - 1005
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20 3.1 0.9 180 - 830
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40 6.2 1.9 50 - 365
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60 9.3 2.8 25 - 180
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80 12.4 3.8 20 - 60
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100 15.5 4.7 20 + 50
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120 18.5 5.7 25 + 165
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140 21.6 6.6 45 + 345
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160 24.7 7.5 150 + 760
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180 27.8 8.5 4270 - 1005</pre>
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<center>
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<img src="gup5-6.gif" width="636" height="766" border="2" vspace="5" hspace="9">
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</center>
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<pre>17 meters: 18.1 MHz
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AZ plots: El. Angle = 19° @ 35';
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14° @ 50'
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EL plots: Az. Angles = 29° @ 35'
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30° @ 50'
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Feedpoint Z (R ± jX): 125 + 5 ohms
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TL = 450 ohm; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 125 + 5
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20 2.9 0.9 145 + 155
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40 5.7 1.8 205 + 335
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60 8.6 2.6 420 + 585
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80 11.5 3.5 1210 + 645
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100 14.3 4.4 1155 - 670
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120 17.2 5.2 400 - 575
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140 20.1 6.1 205 - 325
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160 22.9 7.0 140 - 145
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180 25.8 7.9 125 + 5
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TL = 300 ohm; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 125 + 5
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20 2.4 0.7 140 + 90
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40 4.8 1.5 195 + 185
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60 7.3 2.2 340 + 280
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80 9.7 2.9 635 + 195
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100 12.1 3.7 610 - 215
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120 14.5 4.4 320 - 275
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140 16.9 5.2 190 - 180
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160 19.3 5.9 140 - 85
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180 21.7 6.6 125 + 5</pre>
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<center>
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<img src="gup5-7.gif" width="638" height="774" border="2" vspace="5" hspace="9">
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</center>
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<pre>15 meters: 21.15 MHz
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AZ plots: El. Angle = 18° @ 35';
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13° @ 50'
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EL plots: Az. Angles = 41° @ 35'
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43° @ 50'
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Feedpoint Z (R ± jX): 2330 + 1435 ohms
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TL = 450 ohms; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 2330 + 1435
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20 2.5 0.8 735 - 1300
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40 4.9 1.5 185 - 605
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60 7.4 2.2 90 - 305
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80 9.8 3.0 65 - 120
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100 12.3 3.7 65 + 40
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120 14.7 4.5 75 + 205
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140 17.2 5.2 125 + 435
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160 19.6 6.0 320 + 870
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180 22.1 6.7 2330 + 1435
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TL = 300 ohm; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 2330 + 1435
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20 2.1 0.6 310 - 905
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40 4.1 1.3 75 - 395
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60 6.2 1.9 40 - 195
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80 8.3 2.5 30 - 70
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100 10.3 3.2 30 + 35
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120 12.4 3.8 35 + 150
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140 14.5 4.4 60 + 310
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160 16.5 5.0 170 + 660
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180 18.6 5.7 2330 + 1435</pre>
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<center>
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<img src="gup5-8.gif" width="636" height="768" border="2" vspace="5" hspace="9">
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</center>
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<pre>12 meters: 24.95 MHz
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AZ plots: El. Angle = 14° @ 35';
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10° @ 50'
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EL plots: Az. Angles = 23° @ 35'
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24° @ 50'
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Feedpoint Z (R ± jX): 130 - 180 ohms
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TL = 450 ohm; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 130 - 180
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20 2.1 0.6 110 - 25
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40 4.2 1.3 120 + 130
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60 6.2 1.9 170 + 305
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80 8.3 2.5 325 + 565
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100 10.4 3.2 1020 + 855
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120 12.5 3.8 1490 - 675
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140 14.6 4.4 440 - 670
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160 16.6 5.1 200 - 375
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180 18.7 5.7 130 - 180
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TL = 300 ohm; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 130 - 180
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20 1.8 0.5 100 - 70
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40 3.5 1.1 95 + 25
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60 5.3 1.6 110 + 125
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80 7.0 2.1 170 + 250
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100 8.8 2.7 370 + 410
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120 10.5 3.2 920 + 205
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140 12.3 3.7 575 - 440
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160 14.0 4.3 230 - 320
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180 15.8 4.8 130 - 180</pre>
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<center>
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<img src="gup5-9.gif" width="636" height="756" border="2" vspace="5" hspace="9">
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</center>
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<pre>10 meters: 28.5 MHz
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AZ plots: El. Angle = 13° @ 35';
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10° @ 50'
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EL plots: Az. Angles = 36° @ 35'
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37° @ 50'
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Feedpoint Z (R ± jX): 2070 + 1225 ohms
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TL = 450 ohms; VF = .95
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Deg Feet Meters R ± jX (ohms)
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0 0 0 2070 + 1225
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20 1.8 0.6 835 - 1230
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40 3.6 1.1 215 - 605
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60 5.5 1.7 105 - 310
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80 7.3 2.2 75 - 120
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100 9.1 2.8 70 + 35
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120 10.9 3.3 85 + 200
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140 12.8 3.9 135 + 420
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160 14.6 4.4 345 + 825
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180 16.4 5.0 2070 + 1225
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TL = 300 ohms; VF = .80
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Deg Feet Meters R ± jX (ohms)
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0 0 0 2070 + 1225
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20 1.5 0.5 360 - 895
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40 3.1 0.9 90 - 395
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60 4.6 1.4 45 - 195
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80 6.1 1.9 35 - 70
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100 7.7 2.3 30 + 35
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120 9.2 2.8 40 + 145
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140 10.7 3.3 65 + 305
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160 12.3 3.7 190 + 640
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180 13.8 4.2 2070 + 1225</pre><br>
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<br>
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<center>
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<img src="../images/colorbar.gif" align="middle" width="540" height="4">
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</center>
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<p><i>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.</i></p>
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<center>
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<img src="../images/colorbar.gif" align="middle" width="540" height="4">
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</center>
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<p><a href="groundup.html"><img src="../images/return.gif" align="bottom" width="40" height="40"> Go to series index page</a></p>
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<p><a href="../radio.html"><img src="../images/rtnhome.gif" align="bottom" width="40" height="40"> Return to Amateur Radio Page</a></p>
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<p class="topics-footer">Topics: <a href='../topics.html#dipole'>Dipole</a>, <a href='../topics.html#doublet'>Doublet</a>, <a href='../topics.html#hf-lower'>HF Lower</a>, <a href='../topics.html#hf-upper'>HF Upper</a></p><br>
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