Discussion in 'Survey Center' started by W5RJW, Feb 1, 2010.
Aha. You got me. Yep, a half wave inverted L fed in the center is a dipole.
The IEEE Dictionary says any antenna with the radiation pattern of a dipole is a dipole, by definition.
A duck by any other name?
There seems to be several definitions of a dipole floating around. Here is the ARRL definition:
Dipole—An antenna that is split at the exact center for connection to a feed line, usually a half wavelength long. Also called a “doublet.”
I also saw another one (but I forget where) that said a dipole is a class of antennas consisting of antennas having two poles.
A "dipole" doesn't have to be a "half wave" antenna to be considered a dipole antenna, but this is not to be confused with a half wave monopole antenna design. Feedpoint location for a dipole can be center, end fed, or off center fed but actual feedpoint location doesn't determine if it is a dipole antenna or not. A "common dipole" is considered a half wave antenna that is center fed, but it is not the only type of dipole.
I think I remember the origin of the word "dipole" as being an antenna with two voltage maximum points, i.e. two electric poles, on the standing wave antenna conductor. That results in the familiar figure-8 radiation pattern and seems to fit with the IEEE definition of a "dipole".
Yes, a dipole is defined by current distribution (IEEE) not it's physical construction. An end fed half wave is a dipole just as a center fed half wave is.
The balun transformation ratio depends on what freq you want to use. That's why I stick to single band , coax fed dipoles and loops that require no tuner.
Why is everyone antisymantic? By definition dipoles are center fed, balanced antennas. How can a dipole be "off center fed?"
there is no such thing as a off center fed dipole..the definition of a dipole is two elements of equal length..Off center fed (Wire)..there is no advantage unless your realestate is longer or shorter on one end..>???I dont get it..
Nope, those are the amateur definition. Remember that the 'A' in ARRL stands for "Amateur". The IEEE Dictionary contains the professional level definition and says:
"dipole antenna - Any one of a class of antennas having a radiation pattern approximating that of an elementary electric dipole... having a current node at each end of the antenna." For a standing-wave antenna, a current (magnetic) node is the same thing as a voltage (electric) POLE.
The "definition" of "dipole antenna", based on physical characteristics, is essentially common usage colloquial lingo. You see, the words "dipole antenna" have nothing to do with the physical characteristics - it's not the same thing as a fishin' pole. A dipole is any single element antenna with two and only two electric poles, i.e. standing-wave voltage maximum points. So any conductor, center-fed, off-center-fed, end-fed, or gamma-fed, that has two electric poles, is a dipole, by definition. Note that the "dipole antenna" is professionally defined by its radiation pattern, not by its physical characteristics.