DIY Yagi Antenna for 1200MHz (2400MHz)

Here is another DIY Yagi antenna design for 1200MHz and also suitable for 2400MHz:

Construction details from calculation:


Yagi design frequency =1200,00 MHz
Wavelength =250 mm
Parasitic elements fastened to a non-metallic or separated from boom
Folded dipole fully insulated from boom
Director/reflector diam =4 mm
Radiator diam =3,5 mm

121 mm long at boom position = 30 mm  (IT = 54,5 mm)

Single dipole 116 mm tip to tip, spaced 50 mm from reflector at boom posn 80 mm (IT = 52,0 mm)
Folded dipole 118 mm tip to tip, spaced 50 mm from reflector at boom posn 80 mm (IT = 53,0 mm)

Dir    Length    Spaced    Boom position    IT    Gain    Gain
(no.)    (mm)    (mm)    (mm)        (mm)    (dBd)    (dBi)
1    103    19    99        45,5    2,8    5,0
2    102    45    144        45,0    5,4    7,6
3    101    54    197        44,5    7,1    9,3
4    99    62    260        43,5    8,4    10,5
5    98    70    330        43,0    9,4    11,6
6    97    75    405        42,5    10,2    12,4

The abbreviation "IT" means "Insert To", it is the construction distance from the element tip to
the edge of the boom for through boom mounting

Spacings measured centre to centre from previous element
Tolerance for element lengths is +/- 1 mm

Boom position is the mounting point for each element as measured from the rear of the boom and
includes the 30 mm overhang.The total boom length is 435 mm including two overhangs of 30 mm

The beam's estimated 3dB beamwidth is 49 deg

A half wave 4:1 balun uses 0,70 velocity factor coax and is 87 mm long plus leads
Measurements are taken from the inside of bends
Folded dipole length measured tip to tip = 118mm
Total rod length =259mm
Centre of rod=129mm
Distance HI=GF=46mm
Distance HA=GE=64mm
Distance HB=GD=82mm
Distance HC=GC=129mm
Gap at HG=3mm
Bend diameter BI=DF=23mm

The required balun is made from RG316 coax cable and calculated with a velocity factor of 0.7.

The dipole is made from 10mm² (diameter 3.5mm)  copper wire .

Feedpoint detail:

And finaly the plot of the VSWR measurment to proof the construction:

This Yagi is also suitable for 2400Mhz where the VSWR is a bit worser but still below 2 which is still accetable.

Material costs <10€.

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