> Some of the names are generic and use different words to describe the same
> 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
> 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
> 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.
> Bob, K4TAX
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