In today’s age of mobile devices we can hardly imagine being on the go and not being connected at the same time. It was not always the case. As soon as radio became popular with the masses, the desire for portability, and hence the ability to stay in touch with what was going on in the world from anywhere became a priority. It was however, not a goal that would be easily achieved with 1920s era technology. Pictured above is radio pioneer Edwin Armstrong, along with his wife Marion, enjoying the “portable” radio that he built for her as a wedding present. The radio, along with the few “portable models” produced commercially, weighed between 40 and 60 lbs., including the heavy batteries required to power them. Not something that the average consumer wanted to lug around everywhere that he or she might go.
There were many contributing factors that made the early quest for portability difficult. Foremost was inefficiency. Early tubes and radio circuits consumed quite a bit of power. A single vacuum tube could consume several watts of power, more than an entire modern portable radio uses, and it took several vacuum tubes to make a radio work. A modern radio or mobile device can operate from a single voltage power source such as a 9 volt battery, whereas a vintage radio required several different voltages, including relatively high voltages ranging from 45 to 120 volts. This made for heavy, bulky battery packs. The radio components themselves were not small, the average tube of the day being about 4 inches tall.
Antennas were another problem. Early radios were not all that sensitive and were designed to use long wire antennas that were usually strung between the owner’s house and a nearby tree. Not something that you could easily take to the beach. The antenna problem was solved in part by the wire loop antenna pictured here, ranging in size from about 18 inches to 36 inches in diameter, not small, but better than a 50 foot long wire.
Portability remained a challenge until the 1930s. Three factors came together at this time to solve the problem. The first two were the heterodyne circuit, invented by Edwin Armstrong, and tube technology improvements aimed at maximizing the capabilities of this circuit. They reduced the number of tubes and associated components substantially. The third was an effort led primarily by Sylvania (Sylvania Electric Corporation, a light bulb manufacturer turned tube maker by 1924, was a major player in the vacuum tube market. They did not produce a line of radios bearing their own name until after WWII.), to develop tubes that would operate using substantially less power. These tubes used filaments (the hot glowing part of the tube that emits electrons) that were as fine as a human hair, consumed less than an eighth of a watt (1) and operated with 1.5 volts, that of a typical flashlight battery. They were also designed to work well with plate voltages of 45 to 120 while giving the same performance as standard tubes that used 150 to 300 volts. Different sources list different dates for the introduction of such tubes, but I have found early portable radios such as the Fada Model 126 using them as early as 1934 (2). In 1937, Sylvania introduced a complete line of these tubes. Their low power consumption allowed engineers to design radios that used smaller, lighter batteries. The “less than 10 pound” weight barrier could finally be broken. It was at this time that the portable radio became popular with consumers.
Pictured on the left is the Zenith Model 5G401, Zenith Radio Corporation’s first battery/AC powered portable circa 1939 (3). To the right is the Stromberg Carlson Radio Company’s competing model the 402-H, this particular one is for battery power only. Each radio weighs about 8 pounds. Although the radios required several different voltages supplied be different batteries, the manufacturer would often package the batteries into a single “battery pack." This allowed the consumer the ease of buying the pack that connected to the radio via a single multi conductor plug. Although these radios were portable, they still resembled a standard table radio of that period in size and weight. Radios that could fit in your purse or pocket were still decades away.
This is the back side of the Stromberg Carlson with the cover removed. The flat loop antenna is typical of all heterodyne table radios of the day, portable or AC powered. After removing the back cover, the user then had to remove the antenna to replace the batteries or change a bad tube. This particular model is designed only for battery operation. The idea of miniaturization had not yet begun; all of the components were of the same size as would be used in an AC powered table radio.
If we look inside the Zenith we find that they took an innovative approach to the antenna. The same type of loop is enclosed in a stiff cardboard frame that is equipped with a 36 inch cable and swivel mounted suction cups. The idea was, according to the owner’s manual, to allow the user to stick the antenna on the window of a car, bus or airplane, or to sit it in the window of a steel framed building, thus improving reception. I would not suggest trying to set one of these up on your next transatlantic flight, it might attract unwanted attention, alas, times have changed.
Both models are built in thin plywood cabinets and covered with varnished canvas. This gave the radios a degree of protection from the outdoor elements such as dampness and rain. The Zenith could be operated from batteries or plugged into AC power and also allowed the use of headphones if private listening was desired. Its dial and controls were protected by a cover door when not in use.
Pictured here all buttoned up, the style is referred to as a suitcase radio by collectors. The cover is hinged but not removable. Some brands had removable covers, and many of the covers have been lost over the years. Both of the radios work. The Stromberg required very little work to restore it, but the Zenith required an extensive restoration of its electronics. The cabinets are as I found them, and required only minor cleaning.
Portable radios brought about changes in the way people kept in touch. For the first time, information could be truly “wireless." What we now take for granted, was life changing technology at the time. Never before could the average person listen to their favorite music show at the beach, or enjoy a baseball game or championship prize fight while at a picnic. Now a radio owner could keep up with breaking news and world events even while deep in the woods on a camping or hunting trip, far from civilization and the daily newspaper. The technology was not perfect, operating time ranged from about 30 to 120 hours on a set of batteries. The batteries were expensive at first, but by the late 1930s were becoming reasonably priced. Vacuum tube portables would remain popular until the mid 1950s, when transistors eventually replaced them and made sets smaller and lighter while greatly extending battery life. The last American made tube portable ended production in 1962. (3)
Portable radios began a wireless revolution that continues to this day.
Next month in part two of the story of portable radios, we will look at the Zenith “Transoceanic: line of vacuum tube portables, how they earned the reputation of being “The Royalty of Radios," and the interesting role that they played after the Pearl Harbor attack.
Reference:
1. The Portable Radio in American Life, Michael B. Schiffer, University of Arizona Press.
2. The Radio Collector's Directory, Robert Grinder and George Fathauer, Inwood Press, 1986; Radio Diagrams and Servicing Information Vol. 1 and 2, M.N. Beitman, Supreme Publications, 1941.
3. Zenith Trans-Oceanic: The Royalty of Radios, John H. Bryant and Harold N. Cones, Schiffer Publishing Co., 2008.