My principal interest in insulator collecting is, of course, the radio insulators, and among those the common antenna insulators are my preference.

Much more information is available on these insulators, although the research I have done so far has been quite disappointing in that the bits of information are scattered in a large volume of old publications, so that there is not much to show for all the time I have spent. Having been connected with radio since 1922, when I first started experimenting with mostly home-made parts, has been a good deal of help in putting together the bits and pieces of information. Incidentally, my first antenna insulators were home-made by cutting strips of glass from old broken windshields and drilling a hole through each end.

Radio Antenna insulators were made from the beginnings of Radio (then Wireless) Telegraphy, some time in the first decade of this century. However, it was not until the early Broadcast Radio period (about 1921 - 1930) that such insulators were made in substantial quantities. In those pioneering days of radio, receivers were not very sensitive. Consequently, a rather long, high antenna wire was needed to provide the necessary signal voltage to the input of the radio receiver. To support and insulate this long wire, typically 100 feet, the antenna insulators we now collect were made.

In the heyday of these battery operated radios, getting into the Radio Boom was the IN thing. Most manufacturers who could make something for this new technology - or fad - did so. That is the setting in which most glass and porcelain manufacturers, and even some plastic moulders, made insulators for those large antennas. But with the development of more sophisticated equipment, particularly the invention of the screen grid tubes, very sensitive receivers became practical by the late 1920's. And with this improvement in the radio receivers, the large antennas became generally obsolete. Thus, the large production of antenna insulators lasted less than ten years. It is, of course, impossible to determine the number which were made, but the total production of antenna insulators was probably small compared to that of the pin type insulators.

Transmitting antennas which are too long to be self supporting (low frequency antennas), still use conventional types of antenna insulators. Also, some Hams (Radio ), perimenters, DX (Distance) listeners, and others who are in areas of poor radio reception still use outside antennas, so there are still some antenna insulators being made, and sold.

Considering the short span of time in which most of these insulators were made, there were many types and varieties. In the writer's collection are something over 325 different insulators. This does not include the "egg" types, screw-eye insulators or standoff insulators (See sketches on the following page.). A number of the insulators in the collection are near duplicates. It is difficult to know if these were merely produced by different moulds, or are copies by different firms. Probably some distributors had their insulators made by more than one manufacturer, but to the same drawings and specifications, thus minor variations. There undoubtedly was considerable copying of commercially successful designs, as patentable features were few, and so there was generally no legal obstacle to copying.

About 30% of the collection is of glass. Most are clear, but there are also sun purpled, aqua, green and yellow or straw tints. Two are of very opaque black glass; one is white milk glass. One collector has a honey amber colored insulator, and another has one of cobalt blue.

Another 10% of the collection is made of various compositions, most of these of a mixture that appears to be composed of mica, asbestos, shellac and perhaps other ingredients. Some are of hard rubber, phenolic (?), and one is made of white polyethylene.

The porcelain insulators are most common, making over 50% of the total collection. All are glazed, and the range of colors is about all of the common glaze colors except yellow and red. White and brown are most common. There are cobalt blue, light blue, black, light brown or tan, as well as green.

Unfortunately, few of the antenna insulators carry any lettering or names to permit positive identification. Virtually all of the markings are raised letters and numbers. A few have under glaze rubber stamped marks. It has been possible to identify a few of the unusual shapes by matching them with illustrations in ads or catalogs. Several have "Pat. applied for" or "Pat. Pending", but only some of the Pyrex insulators have a patent number, and this covers the special low loss glass used for their manufacture.

These insulators were made in an amazing range of shapes and designs. Most are relatively long and slender, but some are nearly spherical. From the standpoint of high frequency insulation, the long slender ones are generally best. The length varies greatly, probably based more on technical requirements than on the whim of the designer. The shortest of the regular antenna insulators seem to be about two inches; the longest in the writer's collection is 20 inches; but much longer insulators have been made for use with some of the great highpower transmitters. Since there are two basic types of antenna insulators, a distinction should be made. The small insulators with the wires, when attached, interlooped (like the Johnny-ball insulator), are usually elliptical in shape and are generally known as "Egg" insulators. The other type, having the wires attached at the ends, are generally simply called "Antenna" insulators.

Many of the total of these insulators have been lost through destruction and discard. No doubt many repose in the rather new dumps of the post 1930 era, having been discarded as trash when the unused antenna was taken down. A few may still be found on buildings abandoned during the depression and WW2 years - 1930 - 1945 or so. Some can still be found in attics, still supporting the antenna, some in attic or basement junk boxes. Of course Flea Markets, Garage Sales, Antique Dealers and Second-hand Stores are always possible sources. Ingenuity seems to be the greatest help in locating the four collectable bits of Radio history.