Resonant Dipole Lengths

Wavelengths and half-wavelengths, together with resonant lengths for dipoles

relative to the frequencies for the HF bands

 

The table below gives equivalent wavelengths and half-wavelengths for given frequencies. Half-wavelengths for centre-fed dipoles or vertical antennas are also given and calculated using EZNEC.

 

The usual formula 143/ƒ (MHz) = L (metres) or 468/ƒ (MHz) = L (feet) gives a close enough app.

 

Freq(MHz)
λ (m)
λ (ft/in)
λ / 2 (m)
λ / 2 (ft/in)
Dipole (m*)
Dipole (ft/in*)
Dipole (m#)
Dipole (ft/in#)

1.83

163.82

537' 6"

81.91

268'   9"

80    

262'      

-

-

1.9

157.78

517' 8"

78.89

259' 10"

77     

260'   7"

-

-

 3.52

85.17

297' 5"

42.58

139'   8"

41.56

135' 10"

-

-

 3.65

82.13

269' 6"

41.07

134'   9"

40.08

131'   6"

-

-

 7.02

42.7  

  140' 1"

21.35

  70'   0"

20.76

   68'   2"

-

-

 10.125

29.61

    97' 2"

14.8  

  48'   7"

14.4  

  47'   2"

14.2

46'   7"

 14.05  

21.34

    70' 0"

10.67

  35'   0"

10.35

  33' 11"

10.2

33'   5"

 14.02  

21.11

    69' 3"

10.55

  34' 10"

10.24

  33'   7"

   10.09

33'   1"

 18.1    

16.56

    54' 4"

  8.28

   27'   2"

  8.03

  26'   4"

    7.88

25' 10"

21.05

14.24

    46' 9"

  7.12

   23'   5"

6.9

  22'  8"

    6.78

22'   3"

21.2  

14.14

    46' 5"

  7.07

   23'   3"

  6.86

  22'   6"

    6.73

22'   1"

24.94

12.62

     39' 6"

   6.31

   19'   9"

  5.82

  19'   1"

  5.7

18'   8"

28.05

10.69

     35' 0"

   5.34

   17'   6"

  5.18

  17'   0"

   5.05

16'   7"

28.4  

10.56

     34' 8"

   5.28

   17'   4"

5.1

  16'   8"

   4.99

16'   4"

29.5  

10.16

     33' 4"

   5.08

   16'   9"

4.9

  16'   1"

 4.8

15'   9"

 

The dipole lengths* are calculated for a wire diameter of 2 mm. The dipole lengths# are calculated for a tube diameter of 25 mm. When a larger diameter conductor is used for the antenna element, then the length has to be reduced by an amount known as the K factor (based on the length to diameter ratio).

These lengths are the total lengths - the wire has to be cut in half at the centre to connect the coaxial cable, and that gap in the centre is part of the whole dipole length.

 

You also need to be aware that around 160 mm (6 in.) extra at each dipole leg is required to connect them to the centre or end insulator.

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