By that definition, since they used the word "approximating" the length
could vary over a very wide range, and still fit the definition.
When you make a dipole very short the radiation pattern does not change
much at all. Additional lobes, that would make the pattern no longer
approximate that of an elementary electric dipole, do not start to
appear until the total length is at least 3/4 wavelength long. So it
could be anywhere from perhaps 1/10th to 3/4 of a wavelength and still
fit that definition. That pretty much discredits the notion that a
dipole must be a half wavelength, or resonant, in order for it to be a
dipole.
N6KB
On 9/16/2014 7:53 AM, Steve Hunt wrote:
From IEEE Standard Definitions of Terms for Antennas:
"2.102 dipole antenna. Any one of a class of antennas producing a
radiation pattern approximating that of an
elementary electric dipole. Syn: doublet antenna.
NOTE---Common usage considers the dipole antenna to be a metal
radiating structure that supports a line current distribution
similar to that of a thin straight wire so energized that the current
has a node only at each end."
Steve G3TXQ
On 16/09/2014 05:43, Ken Brown wrote:
Any center fed straight wire is a dipole, regardless of how it's
length compares the the wavelength you are using it on. If I build a
dipole to be a half wavelength on 7 MHz, and then use it on 10.1 MHz
it is still a dipole, just not a half wave dipole.
I find it interesting to examine the dipole antenna. By definition
it is a wire length being equal to 1/2 the wavelength of the
frequency. The name comes from two terms "DI" meaning two and "POLE"
meaning electrical terminal having two distinct regions of
electrical polarity.
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