once upon a time a long time ago i saw somewhere in a magazine or book,
or maybe someone told me, or i heard at a ham club meeting or flea
market, or i had a dream while in heart surgery, or my wife told me that
a 300 ohm TV twin lead dipole is not all twin lead, but the twin lead is
shorter than a half wavelength and at each end a wire continues to make
half wavelength length of the dipole.
anyone do a dipole this way? or heard or read etc etc about this
technique?
With balanced line, that idea makes very little (if any) difference in how
the antenna works around resonance.
This is because the antenna is not in differential mode between conductors.
The antenna is in common mode.
Think about antenna currents and voltages. In order for the velocity factor
to play a role, there has to be a considerable proportion of the electric
field between the conductors. Currents are the same direction and phase.
There isn't much transmission line action between the conductors.
As a matter of fact if you build a normal folded dipole from twinlead and
cut it exactly to resonance, and then cut the wire going past the center and
simply parallel them to make it a normal fat dipole of the same size, the
resonant frequency and bandwidth does not shift. The only thing that
changes is the feed impedance, which goes up about four times.
73 Tom
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Topband reflector - topband@contesting.com
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