Some of the names are generic and use different words to describe the same
item
Here's my take on the topic.
Open wire line: Two conductors stretched tight between two supports with
no insulators or spacers between the conductors. The characteristic
impedance is determined by the size of the wire and the spacing between
the conductors. The dielectric is air. The velocity factor VF is
typically considered to be 0.975 or higher. Conductors can be solid or
stranded. Extremely low loss and can handle massive amounts of power.
Ladder line: Same as above except the conductors are supported with some
type of insulators, ceramic, plastic, paraffin soaked wood, and etc. at
regular intervals. Yes, it looks like a rope ladder. The characteristic
impedance is determined by wire size and spacing. Un-insulated conductors
can be solid or stranded. Spacing between the conductors can be anything
from 6" down to 1".
Window line: Two conductors spaced a constant distance with material such
as vinyl usually about 1" wide. Rectangular or square holes are punched
at regular intervals to reduce wind and water accumulation and to increase
the VF. Conductors can be solid or stranded. Installations benefit by
placing several twists in the line to reduce water accumulation and wind
effects.
TV Twin Lead; Usually vinyl covered conductors using #18 to #24 AWG wire
spaced about 1/2" apart and held in place by some type of insulating
material such a vinyl. Typically not consider adequate for legal limit
operation.
There is also the shielded version of TV Twin Lead that is reported to
reduce pick-up of noise and a version that is oval shaped with the
conductors at the extremes of the oval. The oval center can be air or
foam filled. This type was developed for UHF TV reception in as much as
it has lower loss per unit.
Hope this helps.
73
Bob, K4TAX
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