Hit or Miss
Bric-a-brac: Aerial Insulators from the 1920's onwards
These simple yet
topologically sophisticated pieces of porcelain were very common in the
early days of radio. Weak transmitting powers and basic circuit
design required a big aerial to pick up the best signal.
So big was the problem of
large unsightly aerials that the government set a limit of 100 foot for
Here are two examples of aerial insulators. Porcelain being a very good insulator, it is still used to this day. The white (and more common one) on the left uses a hole and outer guide at right angles. The brown insulator uses a wrap-around system on two orthogonal axis. Glazed porcelain also has the property that water will "bead" rather than coat, minimizing the affect of rain causing a short. It is also easy to clean and keep the chance of conductive contamination to a minimum.
Extract from Newnes