Commercially-manufactured portable valve radios first appeared around 1925 with the introduction of sets like the RCA26 6-valve receiver (see SILICON CHIP, August 2008). However, sets of the RCA26’s calibre were well before their time and weren’t particularly common.

In fact, early portables varied great-
ly both in terms of quality and performance. From 1925 onwards, a few manufacturers dabbled in making "portables" using 2V valves and vibrator power supplies but serious production of Australian-made portables didn’t occur until 1939. That’s because commercially-viable portables had to wait until the introduction of the octal 1.4V battery valves that required only 90V of high-tension (HT) supply.

From that time onwards portables became more popular, although World War II slowed their introduction considerably. The octal 1.4V valves were subsequently commonly used up until around 1950, sometimes in combination with the much later 7-pin miniature types. After that, the 1.4V 7-pin miniatures were used almost exclusively.

The 1950s saw the development of good-performing 5-valve and 6-valve battery-portable receivers. These sets usually used a No.745 1.4V battery for the filaments and two No.482 45V batteries in series to give a 90V HT supply. This combination gave a battery life of around 300 hours.

Mains/battery portables

Because they could so easily be taken from room to room, many people also wanted to use portable sets in the home. As a result, the manufacturers developed portables that could be powered both from the mains and from batteries. This meant that the set could be run economically from the mains around the house, with the expensive batteries reserved for truly portable applications when no mains power was available.