This morning greeted me with this nice little video, where Diana Eng demonstrates the pattern generated by dipole and Yagi antennas by a simple detector consisting of a dipole antenna with a small flashlight bulb wired across the feed point:
httpv://www.youtube.com/watch?v=lslHtCUSfN4
It does actually uncover one of my pet peeves: in describing the action of the reflector element of the Yagi, Diane claims that the reflector “reflects”, but when she added a director, she claimed that the director “focuses”. But if you are a clever person who maybe doesn’t understand much about how antennas work, you might reasonably ask how that actually works. After all, the elements are identical in composition, and are essentially placed the same distance from the antenna. Why does the director direct, but the reflector reflect?
If you can actually answer this question, you’ve begun to understand how antennas really work.
So I’m not an antenna geek, I haven’t actually looked at the problem at all, but they’re not really the same distance from the antenna, right?
I liked the light bulb in the dipole device, and I think Diane does a good job at illustrating the effect, but I agree with Mark that we still need to describe how reflector and directors do their work.
Also: Diane is really looking at near field effects here, right?