[TenTec] Fw: Transmission Line Names

[Robert & Linda McGraw K4TAX]

> 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
>