Design 7 Elements of Yagi Uda Antenna with High Gain

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Input Center Frequency (in Hertz) for Antenna Yagi Design Calculation

Input Center Frequency (in MHz) for Antenna Yagi Design
Input Center Frequency
REFL
DR
D1
D2
D3
D4
D5
RDR
DRD
RE
LAMBDA

Examples The design requirements of yagi-uda antenna: 

Operating freq. 880-960 MHz. 

So center freq. is: 920 MHz 

Wavelength (in meters) = 300 / 920 (MHz) = 0.326 meter 

Reflector length (REFL) = 0.495 x wavelength = 0.161 meter 

Dipole radiator (DE) = 0.473 x wavelength = 0.154 meter 

Director (DIR)=D1=D2=D3=D4=D5 = 0.440 x wavelength = 0.143 meter 

Spacing between elements is the other part: 

Reflector-Dipole radiator = 0.125 x wavelength = 0.040 meter 

Dipole radiator - Director = 0.125 x wavelength = 0.040 meter 

Diameter of elements is: 10 mm

Reference impedance = 50 ohm

Input impedance to our Yagi antenna is 25.7 ohm.

Reflection Coefficient = (25.7-50)/(25.7+50)= -0.321

The voltage standing wave ratio is then equal to: SWR= (1+0.321) / (1-0.321) = 1.9 SWR is big according to our designs requirement which is SWR should be less than 1.5. Therefore I use gamma match Yagi antenna as shown in the figure below to increase the input impedance 25.7 ohm of our antenna to be near the reference impedance 50 ohm. And then we get SWR<1.5

reference : Radio Tengkorak RFWireless Yagi Antenna Design