Plain-language answer: A folded dipole uses parallel conductors joined at their ends and fed in one conductor, producing different feed impedance and bandwidth from a simple dipole.
Why it changes the result
Conductor spacing and diameter ratio affect transformation, so the familiar four-to-one relationship is not universal.
What to verify
Build the documented spacing, sizes, symmetry, feed system, and support geometry; measure at the feedpoint.
The common mistake
Treating it as an ordinary dipole with an extra wire placed anywhere.
Complete-system boundary
Match the exact radiator, feed system, return path, frequency, height, orientation, and environment. Connector or thread fit does not establish electrical compatibility, structural capacity, or safe operation.
