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Building a
Double Extended
Zepp Antenna
The measurements below are for building a Double Extended Zepp . The wire size can range from 16 AWG to 12 AWG . The lower the wire number the wider the bandwidth . For example 12AWG will have a lower swr ( Standing Wave Ratio ) over a greater frequency range than 16 AWG .
The measurments below are in feet and inches . I have rounded off some of the measurments so it will be easier to measure them .
You should install a 4:1 current balun on the end of the 450 ohm latter line stub and the balun needs to be at least twice the operating wattage to prevent the balun from burning up from the swr mismatch on frequencies other than what the antenna was designed for . Don't be cheap , you will not save money if you have to keep replacing the balun .
Remember the longer the antenna is the lower in the band it will operate , you can tune a long antenna with an antenna runer but you cannot tune a short antenna . Best suggestion is to make the antenna for the lowest operating frequency so that you can operate the entire band you desire .
A Double Extended Zepp is a 3 db gain antenna .
The formula for figuring a 5/8 wave per leg is " A = 600 divided by the frequency in megahertz .
The formula for figuring the matching stub is " B = 103 divided by the frequency in megahertz .
Operating
Frequency | Double Extended Zepp 1/2 Antenna Length
A= This measurement | 450 Ohm Latter Line Stub Length
B=This measurement |
| 160 Meters |
| 1.8 Mhz. | 333' 4' | 57' 2 5/8" |
| 1.9 Mhz. | 315' 9 1/2" | 54' 2 1/2" |
| 2 Mhz. | 300' | 51' 6" |
| 80 Meters |
| 3.5 Mhz. | 171' 5 1/4" | 29' 5 1/4" |
| 3.6 Mhz. | 166' 8" | 28' 7 3/8" |
| 3.7 Mhz. | 162' 2" | 27' 10" |
| 3.8 Mhz. | 157' 10 3/4" | 27' 1 1/4" |
| 3.9 Mhz. | 153' 10 1/4" | 26' 9" |
| 4 Mhz. | 150' | 25' 9" |
| 60 Meters |
| 5.4 Mhz. | 111' 1 3/8" | 19' 7/8" |
| 40 Meters |
| 7 Mhz. | 85' 8 1/2" | 14' 8 1/2" |
| 7.1 Mhz. | 84' 6" | 14' 6" |
| 7.2 Mhz. | 83' 4" | 14' 3 5/8" |
| 7.3 Mhz. | 82' 2 1/4" | 14' 1 3/8" |
| 30 Meters |
| 10.1 Mhz. | 59' 4 7/8" | 10' 2 3/8" |
| 10.15 Mhz. | 59' 1 3/8" | 10' 1 3/4" |
| 20 Meters |
| 14 Mhz. | 42' 10 1/4" | 7' 4 1/4" |
| 14.1 Mhz. | 42' 6 5/8" | 7' 3 5/8" |
| 14.2 Mhz. | 42' 3" | 7' 3" |
| 14.3 Mhz. | 41' 11 1/2" | 7' 2 3/8" |
| 17 Meters |
| 18.068 Mhz. | 33' 2 1/2" | 5' 8 3/8" |
| 18.130 Mhz. | 33' 1 1/8" | 5' 7 1/8" |
| 15 Meters |
| 21 Mhz. | 28' 6 7/8" | 4' 10 7/8" |
| 21.1 Mhz. | 28' 5 1/4" | 4' 10 1/2" |
| 21.2 Mhz. | 28' 3 5/8" | 4' 10 1/4" |
| 21.3 Mhz. | 28' 2" | 4' 10" |
| 12 Meters |
| 24.890 Mhz. | 24' 1 1/4" | 4' 1 5/8" |
| 24.950 Mhz. | 24' 1/2" | 4' 1 1/2" |
| 10 Meters |
| 28 Mhz. | 21' 5 1/8" | 3' 8 1/8" |
| 28.5 Mhz. | 21' 5/8" | 3' 7 3/8" |
| 29 Mhz. | 20' 8 1/4" | 3' 6 5/8" |
| 29.5 Mhz. | 20' 4" | 3' 5 7/8" |
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