Talk:Yagi antenna
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[edit] Traps
A trap is not just a coil, it is a combination of a coil and a capacitor in parallel. The values for the capacitor and coil are chosen such that the trap is resonant in the middle of the band for which it is designed.
For example, if you were to design a triband yagi for 14, 21 and 28 Mhz, you would have the 2 28 MHz traps located closest to the boom, then the 2 21 MHz traps, followed by the final length of element beyond the trap.
The resonant circuit of the trap isolates the outer portions of the element from the inner portion. If you were to look at the representation for an yagi antenna element, you would see that it has 2 traps on each side of the boom. The trap's function is to isolate the outer portion from the inner portion of the element. For example, if you were to use this antenna on 21 MHz (i.e. the 15 meter band), only the portion of the antenna between the '21MHz' traps is active.
"------21MHz-----28MHz-----X-----28MHz-----21MHz------"
X = Boom
A dip meter is typically used to determine the resonant frequency of a trap.
Source: The ARRL Handbook for Radio Amateurs (1991). Antenna Fundamentals p. 17-14. Newington CT: American Radio Relay League.
[edit] Energy Flow Diagram
Nice article! Possibly a bit too deep too quickly. Remember, we are not all wireless communications experts ;-)
Can you please provide a key for the energy flow diagram on this page? What is electric field, what is magnetic filed, what is physical antenna etc...
Perhaps we could also provide a link from here back to Tesla's experiments with wireless transmission of electrical energy.
darkside2010 00:26, 2 January 2006 (UTC)
[edit] Element Spacing & Design
The statement about spacing between elements being "approximately 1/4 of a wavelength" is wrong. While spacing varies depending on design, the normal spacing is about 1/8 of a wavelength.
A good source we should footnote is http://www.cebik.com. Mr. Cebik has written a large number of articles on antenna design, many of which cover details of Yagis in far more detail than is appropriate for an encyclopedia.
Off2Explore 19:16, 27 April 2006 (UTC)
