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Vintage Radio

Pocket-sized valve portable radios. During the era before transistors took over, manufacturers went to extraordinary lengths to produce portable valve radio receivers. None went further than the Japanese, although their miniature valve portable receivers were never marketed in Australia.

By Rodney Champness

"Portable" radios first started to appear in numbers in the 1930s, although a few innovative portables did appear as early as the mid 1920s. These early sets were quite bulky and heavy and by today’s standards, were portable in name only.

Click for larger image
This is the view inside the Global miniature portable. The components are tightly packed together.

Some of those original sets used 2V valves and required a 2V wet cell (A battery) for the filaments. They also required around 135V from a dry battery pack (B battery) for the high-tension (HT) plate and screen voltages. Certainly, people had to be serious about their desire to have radio "wherever they went". Radio stations of the time were fairly low-powered and programming was limited, which restricted the usefulness of early portable sets.

In addition, the battery requirements were quite onerous. The wet cell required regular maintenance and care, including measuring the specific gravity of the electrolyte, keeping the top clean and dry, recharging it at regular intervals and making sure the set was not tipped over.

Tipping the cell (battery) over meant that acid would leak out of the battery and damage the set as well as the battery itself (sulphuric acid is quite corrosive). By contrast, the better designs used dry batteries for the filaments, usually two 1.5V cells in series. The 2V supply for the valve filaments was obtained simply by connecting a resistor in series with this 3V supply.

The dry batteries used for the HT supply required no special maintenance. However, they were heavy and expensive to replace.

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