Back in the 1960’s antenna sites started getting a tad crowded, and one solution proposed was to connected many transmitters to a single antenna, using a parallel network of bandpass filters that would allow isolation between transmitters.  After looking for ways to accomplish this at VHF, it was found that resonant cavities could be formed using a readily found, well constructed, tight tolerance, cheap and widely available solution — beer kegs.

It was found that a coaxial resonantor could be formed by making a center conductor that is adjusted to tune the frequency. As the article states, many problems were overcome in order to make them as successful as they were, and the article estimates tens of thousands of radio transmitter sites around the world equipped with these bands of beer kegs transformed into resonators!