Large And Small Corning Pyrex Radio Glass Antenna Feed Thru Insulator Bowls
by Brent Dingman

Reprinted from "INSULATORS - Crown Jewels of the Wire", November 1972, page 9

In 1928 these heavy yellow tinted glass insulator bowls (bushings) were used on large radio station towers, and the smaller ones were used by radio (HAMS) experimenters on their antenna systems. They were advertised in radio parts catalogs and QST (hams magazines) In the late 20's to 30's.

Each large Corning Pyrex insulator bowl (reference sketch 2) is serialized: top bowl PAT 1700055, bottom bowl PAT 1700056, PYREX MADE IN U. S. A. Overall height is 10 inches, width 9-1/8" and weight 9.5 lbs., making it the largest glass insulator in the PYREX family. This is comparing it to the largest known Pyrex 453 and 441 power type (as seen in May issue 1972, Insulator magazine, page 10). When mated, total weight is 20 lbs., and the glass thickness is 5/16". Comparing it to the large power Pyrex-type 453 which is used and insulates high-voltage KW, the Pyrex-radio antenna-type insulates high radio-frequency RF energy transmitted.

The smallest number of the Pyrex-radio insulator glass family (reference sketch 1) measures 4 inches in overall height, is 6 inches wide and weighs 2.25 pounds. When mated with the complete hardware, the total weight is 5 pounds. The 3/8th inch threaded-brass-rod is the HOT conductor, and the thickness of glass is 5/16".

All the insulator bowls have a yellow tint, and I don't know if they would be classed carnival glass. I have ten pairs of these large insulator bowls with no hardware and five pairs of the smaller bowls, only one of which has hardware and is assembled complete, as per photograph, shown above sketch 1.

I would appreciate hearing from anyone having additional Information regarding these Insulators.

Large Pyrex-Radio-Antenna Insulators, bottom view, not mated.