Yagi antenna
The geometry design is more easy than the construction.
Design: There are lot of software, from freeware to expensive, professional packages.
I useed YAGIMAX2, it's freeware. Query on google. in negative case i may upload a copy.
Of course, in the case of wire antennas, the NEC is the mather of all software.
Construction:
Great attention to 3 points:
- The connection of each director to the support tree. Someone use short circuited connection, some other use an isolated support. The professional one antennas use isolators with low loss (i.e. fiberglass) and formed in a manner that the rain never wet the isolated path.
-The balun: many types exist. The folded coax cable has a moderate bandwidth. The Lumped elements one may be better.
-Impedance matching: is the coax cable 50 or 75 Ohm? This may be determinant to choose the dipole geometry.
thanks dear sergio mariotti for info
i think there is some useful handbooks about yagi antennas on the net , but hard to find for me .
have u any idea's ? or help
Idea about what? Books? Or sofware? Or practical suggestion?
If your interest is academic, a very large amount of books, papers, exists.
But very often the Electromagnetic field is "generous" and tolerate great approssimations. So my suggestion for practical building of Yagi antennas is refer to practical references rather than academic text. The "VHF Manual" a book for amateur radio give very deep suggestion how build yagi antennas.
Another source of information is the critical and close observation of the details of a factory made yagi antenna.
Don't forget to pay attention to non-electromagnetic aspect like human seafty (i.e. wind resistance and radiation hazard).