Lightweight 4 Element Yagi for 144.3MHz
Materials and description
The choice of the materials used should be a compromise between weight and robustness. So this ended up at 1.4mm stainless steel rods and 11mm PE installation tubing as used by electricians. For the beam to be portable, it is convenient to spit the boom into two pieces. The ideal solution (in my mind) is to used the ends for the middle of the boom, as they are already made to stick into eacs other. I drilled a whole through the joint boom at the overlapping region. One now can kill two birds with one stone by impaling the yagi at this specific drilling to hold the boom parts together and the antenna to the sky (see sketch). The elements sticked through drillings in the boom and fixed by hotglue. The driven element is tuned by sliding the rods in and out, until matched. Fixed then by luster terminals. The driven element is built similarly to the 3-element-yagi presented in the ARRL handbook 2000.
Dimensions
| Element | Material | Dimensions | Dist. to reflector |
| reflector | 1.4mm steel rod | 1035mm | 0mm |
| driven element | 1.4mm steel rod | 2x50mm | 416mm |
| 1st director | 1.4mm steel rod | 936mm | 831mm |
| 2nd director | 1.4mm steel rod | 926mm | 1290mm |
| boom 1 | 11mm PE tubing | 700mm | -- |
| boom 2 | 11mm PE tubing | 700mm | -- |
Simulation
The dimension of the driven element was measured after SWR-tuning. The construction allows easy tuning as the element is fixed using a luster terminal. -------------------------------------------------------------------------------YAGIMAX 3.0 CALCULATION OF 4 ELEMENT YAGI
ULTRA LIGHT YAGI AS BUILT
07-20-2000
13:37 FILE: DL1GSJ_R.INP
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ELEMENT: LENGTH (Cm.) SPACING FROM REF. (Cm.) ELEMENT DIA. (Cm.)
Reflector: 103.5000 0 0.14000
Driven Ele.: 99.0000 41.6000 0.14000
Director #: 1 93.6000 83.1000 0.14000
Director #: 2 92.6000 129.0000 0.14000
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Normalized Radiation Resistance at 144.300 mHz is 55.71 Ohms
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FREQ (mHz) GAIN (dBi) F/B (dB) IMPEDANCE (ohms) VSWR
144.000 9.09 12.04 49.69+j14.17 1.04
144.050 9.09 12.07 49.89+j14.43 1.03
144.100 9.09 12.09 50.09+j14.69 1.03
144.150 9.10 12.12 50.29+j14.94 1.02
144.200 9.10 12.15 50.48+j15.19 1.01
144.250 9.10 12.17 50.67+j15.44 1.01
144.300 9.10 12.20 50.86+j15.68 1.00
144.350 9.10 12.23 51.05+j15.92 1.01
144.400 9.10 12.25 51.24+j16.15 1.01
144.450 9.10 12.28 51.43+j16.38 1.02
144.500 9.10 12.31 51.61+j16.61 1.02
144.550 9.10 12.33 51.79+j16.83 1.03
144.600 9.10 12.36 51.97+j17.05 1.04
144.650 9.10 12.39 52.15+j17.26 1.04
144.700 9.10 12.42 52.32+j17.47 1.05
144.750 9.11 12.45 52.50+j17.68 1.05
144.800 9.11 12.48 52.67+j17.88 1.06
144.850 9.11 12.51 52.83+j18.08 1.06
144.900 9.11 12.54 53.00+j18.27 1.07
144.950 9.11 12.57 53.16+j18.46 1.07
145.000 9.11 12.60 53.32+j18.64 1.08
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