Introduction

I had been collecting radio antenna insulators and lightning arresters for about fifteen years when I was informed that what I really collected was “radio strains” - truly a name that only a mother could love. Well, I am pleased to have this opportunity to take a break from my other “job,” editing Old Familiar Strains, a collector’s newsletter, and show you that radio strains aren’t as bad as they sound.

History

The history of antenna insulators starts with the history of radio itself. Just before the turn of the century, the radio pioneers began demonstrating their new science. In order to work properly, most antennas must be elevated above surrounding objects and must be insulated from the ground. Radio antenna insulators provide a means to suspend the antenna and insulate it. [Somehow it just seems fitting - pin insulators were an outgrowth of telegraphy - radio strains an outgrowth of wireless telegraphy].

Radios and crystal sets did not become commonplace in homes until the mid 1920’s. As a consequence, the earliest examples of radio antenna insulators (dating from the teens) originate from military, commercial, or amateur radio installations.

As would be expected, the same materials that were proven in use for telegraph and power work were found to make good insulators in low frequency radio work. Early insulators were commonly made from wood, mica, rubber, and composition. Later, porcelain, glass, and finally fiberglass and plastic were used.

Most of the examples of non-military insulators found today date from the 1930’s. The popularity of short wave listening in the 1930’s and during World War II resulted in the sales of lots antenna insulators and antenna kits. An antenna kit typically included antenna wire, a pair of end insulators, some type of lead in, a lightning arrester, a ground strap and installation instructions. Figure 1. shows a home installation.

Figure 1. Wards Airline Antenna Kit, Part No. 62-422

Although antenna insulators are still used by amateur radio operators, and you can still find them at electronics stores, two events from the 1950’s spelled the decline for outdoor antennas and antenna insulators. First, for many families the radio cabinet in the living room and the evenings spent listening to radio programs were displaced by the television in the 1950’s. Second, the development of improved in-cabinet radio antennas meant that most local stations could now be picked up without using an outdoor antenna.

Types of Radio Antenna Insulators

Although there are specialists among antenna insulator collectors, the generalists among us usually include the following items in our collections:

end insulators

As shown in Figure 1., end insulators are used to support the ends of a wire antenna. Most have a hole through each end and sizes range generally from 1" up to about 12". (I once saw a 5 footer!) Although designs differ, there are two main types; those that work in tension and those that work in compression (see Figure 2.).

Figure 2. Illustration from “Allied Radio Catalog #110”,
 1943, Chicago, IL, pg. 56.

End insulators were made by hundreds of domestic manufacturers and the variety of styles is immense. Unfortunately for collectors, more often than not, the insulators were not marked with a name or trademark, making identification difficult.

feed line insulators

The line that connects the outdoor antenna to the radio is called a “feed line” or a “lead in.” Collectors use the term stand-off insulators to describe the insulators that hold the feed line out away from the wall. In function, a stand off insulator is similar to a small pin insulator. (See Figure 1.). Feed through insulators are sometimes used to bring the feed line through the wall into the house. These are similar to the “knob and tube” insulators that were once used for house wiring.

Lightning Arresters

Lightning arresters provide a path for lightning to get to ground without (hopefully) following your antenna into the house, the radio, the dog, you, etc. A lightning arrester is shown in Figure 1.

There are three main types of arresters. The most common style for radio work has two “binding post” connections on the top. The second type has three binding posts and is called a “doublet”. A third general type is specially designed for use with television feed line. The television type usually incorporates special grooves to hold various types of “twin lead.” All three types are similar in function and construction. Most arresters were made of porcelain. Some types from the 1930’s were made of clear glass. Others, from the 1950’s were made of bakelite or other plastics.

Lightning arresters were frequently made by the same companies that made antenna insulators. As mentioned above, arresters often came packaged together with insulators in antenna kits.

Collecting Antenna Insulators

Talk about a young hobby. Our hobby newsletter, Old Familiar Strains, was launched about three years ago. That endeavor marks the beginning of our efforts to get organized as a collecting community. (And we are still far from organized). When the newsletter started, many of the readers had been collecting for years with little or no previous contact with other collectors!

One of the missions of Old Familiar Strains, is to promote the exchange of information about our collections so that we can build a cataloging system. It is hoped that, one day, a system similar to the ones that exist for cataloging pin insulators will be developed for strain insulators.

Your first radio strain will probably be a 2 to 3 inch glass or porcelain insulator found at a yard sale or at a flea market. But, don’t waste your time looking at antique shops.

On a recent trip to southern California, we stopped at a few antique shops along Interstate 5. Always the optimist, I answered honestly when the proprietor of one shop asked “What are you looking for?” After repeating myself slowly several times, I think that he finally began to understand that I was looking for “those funny glass jobbies that folks used to use to hold up radio antennas out on the farm.” Then he related the oft told tale of the “bucket full” that he threw out because “nobody wants them.”

Conclusion

If radio antenna insulators (okay, strains), look like they would be fun to collect you are right! See, I told you that they weren’t as bad as they sounded.