The long name is “Linear Antenna Array with Series Excitation”, but its popular name is Franklin Antenna. Gain of this antenna is 5.3dBi, and can be increased with adding additional A, B and C sections i.e. increasing the number of dipoles - A. Our antenna has 3 dipoles – two A sections and one D-D section.

Number of Dipoles 3 5 7 9
Gain 5.3 6.5 8.0 8.1


We can see that increasing the number of dipoles beyond 7 returns almost no increase in gain.

Its mechanism of work is very simple: it exploits the sinusoidal wave – when the positive part of the wave is in half-wave dipole A, the negative is in B-C-B section – the positive sections add up, while the negative radiation cancels itself – the gain is increased.

Antenna should be matched with 4:1 BalUn. It is good practice to place it in a PVC pipe.

09 franklin

Antenna should be placed vertically to be omnidirectional and with vertical polarization

Measurements:

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10 radiation pattern 11 radiation pattern

 

Vertical and Horizontal Radiation pattern

13 radiation pattern

Radiation pattern in 3D


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