Multi-Band OCF-dipole Antenna

Looking for a good multi-band wire antenna that covers 80, 40, 20, 17, 15, 12, 10, and 6 meters?  You will like this one.  It’s cheap and easy to build.  All you need is 133’ of wire, (2) insulators, center connector (ladder lock), 450 ohm ladder line,  4:1 current balun and an unbalanced tuner or a balanced tuner.

KI4PMI and I built one of these antennas and analyzed it on the bands listed above.  We like to compare the EZNEC model SWR predictions to the SWR measurements made with an AIM-4170C antenna analyzer.  The SWR comparisons for each band are included below.  We tested the antenna using 90 watts and found that every band tuned easily wth an LDG AT-100PRO autotuner.  We were able to make numerous SSB phone contacts during the brief test including contacts with Saudia Arabia, United Arab Emirates, Crotia, Columbia, and Paraguay.

Caution: Keep the ladder line away from trees, structures, metal objects, and off the ground.

ocf-dipole-diagram

The EZNEC model predictions for the 80, 40, 20, 17, 15, 12, 10, and 6 meter bands are displayed below.  Predicted power delivered to the antenna (%) was calculated with the free TLDetails program (courtesy of AC6LA) using EZNEC predicted values as input.

EZNEC models for each band are available in a zipped file for download at the link below.

ocf-eznec-models

NOTE:  The characteristic impedance and velocity factor (VF) of ladder line made by different manufacturers can vary significantly.  These variations are caused by the material used, insulation, distance between parallel wires, etc.  The characteristic impedance of 450 ohm ladder line can vary from 360 ohms to around 400 ohms.  The velocity factor can vary from around .89 to .92.

80 meter band

80m-swrmeasured 80 meter SWR curve

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Predicted 80 meter power to antenna feedpoint
Frequency (MHz) Power (%)
3.50 94.5
3.75 84.6
4.00 76.9

40 meter band

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measured 40 meter SWR curve

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Predicted 40 meter power to antenna feedpoint
Frequency (MHz) Power (%)
7.00 97.62
7.15 98.14
7.30 98.26
 

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20 meter band

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measuredl 20 meter SWR curve

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Predicted 20 meter power to antenna feedpoint
Frequency (MHz) Power (%)
14.00 92.45
14.17 93.71
14.35 94.81
 

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17 meter band

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measured 17 meter SWR curve

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Predicted 17 meter power to antenna feedpoint
Frequency (MHz) Power (%)
18.068 94.65
18.113 95.06
18.168 95.54
 
15 meter band

imagemeasured 15 meter SWR curve

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Predicted 15 meter power to antenna feedpoint
Frequency (MHz) Power (%)
21.000 91.97
21.225 92.78
21.450 93.94
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12 meter band
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measuredl 12 meter SWR curve
Predicted 12 meter power to antenna feedpoint
Frequency (MHz) Power (%)
24.89 92.07
24.93 92.28
24.99 93.94

 

image10 meter band

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measured 10 meter SWR curve

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Predicted 10 meter power to antenna feedpoint
Frequency (MHz) Power (%)
28.00 90.75
28.85 89.54
29.70 88.69
 
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6 meter band

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measured 6 meter SWR curve

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Predicted 6 meter power to antenna feedpoint
Frequency (MHz) Power (%)
50.0 87.95
52.0 94.46
54.0 90.66
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1 Response to “Multi-Band OCF-dipole Antenna”


  • Very helpful information! I’m working around HOA restrictions and need to move the feedpoint of my extended double Zepp closer to the house; 50′ may be perfect. I may try using 300 Ohm TV twinlead to minimize visibility and run that into the shack and my Johnson Matchbox.

    Thanks,

    Jim
    KL7JBB

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