Zipper Type Air Core CATV Coaxial Cable

Who manufactured this cable and when?

Please note that the mystery is now solved. Just keep scrolling for the answer.Thanks.

Inner Conductor - Copper.

Dielectric - Separate operation injected low density polyethylene, equally spaced (but slightly loose) along the inner conductor. The disks are sort of held in place by the outer conductor.

Outer Conductor - Copper tape rolled into a circular shape with fingers along the longitudinal edges interleaved and roll crimped down. (Interleave your fingers and you will see what we mean.) The coax is not waterproof and relies only on its jackets and polybutene flooding for moisture protection. I have seen the 375 and 412 sizes.

This is a very old and obsolete product and it is often referred to as "PD cable" which apparently stands for pressurized design. If however clean dry air is introduced into the cable, the disks tend to slide along the inner conductor until sufficient free distance is reached for the inner conductor catenary to short against the outer conductor. Thus there seems little chance of blowing water out of an installed cable.

We have talked with the local CATV company and we should get a cable sample from the systems installers the next time one of these cables is replaced. We will open and photograph the sample and link the picture to this message thread.

Kindest regards,

Peter Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

Trilogy Communications in Pearl MS has manufactured, and still does to my knowledge, cables such as these. The disks as I recall are injection molded and are not necessarily loose, but fused to a thin adhesive PE layer over the conductor.

see www.trilogycoax.com for more info.

Erik Macs
VP Sales and Marketing
Thermoplastics Engineering Corporation
11 Spruce St.
Leominster, MA 01453 USA
978-537-8135 x13
fax: 978-537-5484
This email address is being protected from spambots. You need JavaScript enabled to view it.

Thanks for the information Erik! We are well familiar with the Trilogy products in Pearl (near Jackson), MS as I have toured both their plants. The Pearl Plant was as I remember a LBO from General Cable Corporation and the GC fused disk design was a technical revolution when it was first released I believe in the early 1970s. The reasons for this were the remarkable structural return loss (SRL) characteristics of their CATV coax products.

The Trilogy folks are very progressive and they have made many design improvements to the product line over the years, mainly to prevent water migration down the coax core.

Their outer conductor is however continuously TIG welded aluminum and we are unaware if GC ever made a zipper design outer copper conductor in lieu of welding.

Alcatel Kabelmetal (Hanover) also made a disk type cable at some period but they are continuous TIG welding specialists and the outer conductior was always welded.

Does anyone have information on the zipper type outer conductor?

On a slightly different subject, do any of you remember styrofoam insulated CATV cable? I actually saw this manufactured many years ago in a plant in Chicago.

Kindest regards,
Peter Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

We have taken a picture of this cable and given a detailed description of it at:

www.stewart-hay.com/zipper1.htm

Kindest regards,
Peter Stewart-Hay
Principal
Stewart-Hay Associates
www.Stewart-Hay.com

**** Mystery Solved ****


We have just learned that this type of cable was built in Australia and installed between the major cities there in the 1960's, the 1970's and in shorter lengths in the 1980's.

Wow! This was a really tough one to identify.

If you have an electrical/ electronic cable that you would like identified, please contact us with close up photos at Stewart-Hay Associates


Kindest regards,
Peter Stewart-Hay
Principal
Stewart-Hay Associates