15-02-2013, 04:27 PM
Yagi-Uda Antenna Theory, Design and Results
1Yagi-Uda.pdf (Size: 233.82 KB / Downloads: 92)
History
Invented by Shintaro Uda and Hidetsugu Yagi in 1926
Relatively unknown until World War 2
Now used for amateur radio, TV, satellite comm., ..
Dipole
Two conductors of length =4
One connected to signal, the other to ground
The only driven element in the system, no electrical
connection to directors or reflector
Directors
Lengths smaller than dipole, continuously decreasing
Excited by the field of the dipole
Make antenna directional
Reflector
Larger than dipole
Prevents antenna from sending backwards
Key Parameters
Gain: About 20 dBd
Resonance frequency: 2.43 GHz
Input impedance (after tuning):
49 i6
Found AP at 5.5 km distance :-)
Lessons Learned
Element lengths and spacings are
critical
Yagi has good directivity
Professional equipment very helpful
during construction