9 elements yagi 435 mhz
This is the antenna...
│ ┌─────────────────────────────┤
│ OPERATING FREQUENCY........... {MHz} 435 │ │
│ REFLECTOR LENGTH.............. { m } .345 │ FORWARD GAIN = 11.29 dBi │
│ FED ELEMENT LENGTH............ { m } .33 │ │
│ REFLECTOR SPACING............. { m } .086000 │ F to B RATIO = 72.24 dB │
│ #of DIRECTORS 7 Rfl EL DIAM {mm } 5 │ │
│ D 1 SP { m } .069000 D 1 LEN { m } .315 │ INPUT IMPEDANCE = │
│ D 2 SP { m } .081000 D 2 LEN { m } .296 │ 83.8 +j 26.6 Ohms │
│ D 3 SP { m } .095000 D 3 LEN { m } .289 │ │
│ D 4 SP { m } .112 D 4 LEN { m } .282 │ ARRAY LENGTH = 0.91 m │
│ D 5 SP { m } .131 D 5 LEN { m } .259 │ │
│ D 6 SP { m } .155 D 6 LEN { m } .254 └─ F4: Optimize ───── F6: BW ─┤
│ D 7 SP { m } .181 D 7 LEN { m } .236 ┌─ F3: Plot ───── F5: Mode M ─┤
Bend dia 40mm; Folded dipole.
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│ ┌─────────────────────────────┤
│ OPERATING FREQUENCY........... {MHz} 435 │ │
│ REFLECTOR LENGTH.............. { m } .351 │ FORWARD GAIN = 13.20 dBi │
│ FED ELEMENT LENGTH............ { m } .326 │ │
│ REFLECTOR SPACING............. { m } .087000 │ F to B RATIO = 58.45 dB │
│ #of DIRECTORS 9 Rfl EL DIAM {mm } 10 │ │
│ D 1 SP { m } .069000 D 1 LEN { m } .314 │ INPUT IMPEDANCE = │
│ D 2 SP { m } .079000 D 2 LEN { m } .304 │ 57.7 +j 23.1 Ohms │
│ D 3 SP { m } .089000 D 3 LEN { m } .297 │ │
│ D 4 SP { m } .102 D 4 LEN { m } .294 │ ARRAY LENGTH = 1.20 m │
│ D 5 SP { m } .116 D 5 LEN { m } .285 │ │
│ D 6 SP { m } .133 D 6 LEN { m } .285 └─ F4: Optimize ───── F6: BW ─┤
│ D 7 SP { m } .151 D 7 LEN { m } .278 ┌─ F3: Plot ───── F5: Mode M ─┤
│ D 8 SP { m } .173 D 8 LEN { m } .289 │ Tab: Steps El's │
│ D 9 SP { m } .197 D 9 LEN { m } .263 │ │
Bend dia 50mm; folded dipole.
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Mishu~
4:1 balun it will match 50 ohms to 200 ohms. The usual impedance of a folded dipole is somewhere between 200 and 300 ohms. In your simulation you get much smaller than this.
Connecting the second antenna with a 1:1 balun, or just a ferrite core around the coax cable isn't bad as a first step.
You may want to adjust either the dipole dimensions or use a tuning network to improve the matching, but doesn't make sense without an actual impedance measurement.
well... according to the simulation, i'll make it... then since folded dipole, then i can not actually change the length. so how can i first measure the impedance and then based on that reading, how to make it ok for 50ohm?
Can you aq_mishu supply me this yagi calculation program
please send me your email address and i'll send it through email... infact you can do a search using "QY4 Yagi". It is a DOS based program.