Collecting Prewar Personal Portable radios

Although personal electronics got its start prior to WWII its impetus was cut short.  In April of 1942 production of radios as well as most other consumer electronics was stopped for the duration of the war.  Production of electronics for civilian uses did not resume until late 1945.  So, for almost three years there were no new radios, televisions, or phonographs.  When production resumed the demand was so great that shortages developed due to lack of critical components.  Nevertheless, the post war radio production was huge compared to the number of prewar radios produced.

Personal radios, like the RCA BP-10, were only available from the summer of 1940 until the April 1942 production stoppage.  RCA redesigned their line of personal radios after the war and came out with a series of personal portables including their models 2B401, B411, and the gold plated 54B5.

            Other manufacturers dusted off their prewar personal radio designs and produced them essentially unchanged from their prewar versions.  Examples include the Motorola model 5A1, which was identical to the prewar A1.  Some manufactures redesigned their personal radios to add improvements.  The Emerson model 508 of 1946 is basically an improved version of the prewar model 432 personal radio.  A few manufacturers just ignored the personal radio market to concentrate on television and other electronics.  Zenith was one such company.  Zenith produced their model 4K600 “Poketradio”  personal portable prior to the war, but did not offer another personal portable radio until transistors were available in the mid 1950s.  Instead, Zenith concentrated on sales of their large multi-band “Transoceanic” portable radio.

Since, the production of prewar personal portables lasted only a few years the number available to collectors and restorers is very limited.  Also, many were thrown away due to battery corrosion and obsolescence (transistors were the new craze).  By the 1960s the high voltage batteries required for the tubes were expensive and becoming hard to find.  Those surviving are primarily the radios produced in the highest volume.  The RCA BP-10 is a good example of a popular prewar personal portable that is often seen on eBay and other sales venues.  Production totaled more the 200,000, which is pretty amazing for the time.  Other portables that seem moderately common include the Motorola A1, Emerson 432, and Zenith model 4K600 “Poketradio”.  There are a lot of very rare sets that apparently were poor sellers or not rugged enough to survive.  Among those might be the Crosley model 45 “Commuter” and the Lafayette model E-191. 

  A few pre WWII personal portable radios including: A. Knight - B10506, 

B. Fada - 33, C. Motorola - A1, and D. Emerson – 432

Collecting and restoring personal portable radios has some advantages over collecting and restoring table top or console radios.  Obviously, personal portable radios are much smaller.  Also, they also tend to be cheaper, because there currently isn’t much interest in them compared to other types.  Transistor radios seem to be an exception.  But, the transistor radio collectors generally ignore most of the early tube based portables. 

There are a few drawbacks to collecting tube portables.  One drawback, as previously mentioned, is their comparative rarity.  Personal portables were manufactured for two years before WWII and for about ten years after the war.  They were not promoted heavily by the radio manufacturers, probably because they were rather inexpensive to begin with.  Lastly, they were generally a secondary radio sold to those going places without reliable AC power.  Since they were inexpensive many were replaced by transistor radio when they became available.  The tube portables were often junked.  The really rare tube portables seem to be the personal portable battery only models.  Since these could not be run from the AC line they were of limited interest to the buying public.  True battery only portables appeared in 1939.  By 1942, when radio production was suspended for the war, sales of battery only portable radios were only about a third the number of portables capable and battery and line AC/DC line operation.  Most of the battery only radios seem to have been bought as personal radios for travel, camping, and other activities were small size was of overriding importance.

Electrical restoration of battery powered tube portables is usually straight forward.  The original circuit components were rarely stressed to the same degree as in AC line operated radios.  The low power dissipation and circuit voltages were generally much less than the components were designed to handle.  Many 70 and 80 year old portable radios will play just fine with most of their original parts.  The exception is polarized capacitors.  They almost always need replacing.  Fortunately, most battery only radios rarely have more than one polarized capacitor.  After replacing that capacitor the radio will most likely play as it did when new. 

An early tube portable radio in working condition is a true window into the history of portable electronics. The next time someone demonstrates their latest smart phone it might be a good time to show them where it all started.  The fact that hand carried electronics existed that long ago is often a surprise to non radio enthusiasts.  

Personal Portable Electronic Evolution

The BP-10 Becomes Obsolete

After WWII the public need for and interest in portable radios waned somewhat, but did not go away.  The portable radios were still too heavy and battery life was too short to be of use to anyone except the die hard radio fan.  That changed in 1947with the invention of the transistor.  By 1955 about a half dozen radio manufacturers were producing small transistor portable radios with long battery life.  Finally radios were truly portable and small enough to be carried almost everywhere.  Initially, the new transistor radios were expensive. But, by the late 1950s the cost of the transistor radios was driven down to very low levels by the Japanese radio industry.  Almost everyone could afford one.  In fact, the price was driven so low that by 1970 most American manufacturers no longer built portable radios in the U.S. ¹  Most were made in Japan.

The Japanese built on their success with the transistor radio when Sony introduced the Walkman in 1979.  The very portable and personal Walkman changed forever how the world listened to recorded music.   When compact discs (CDs) replaced audio tapes Sony quickly came out with the Discman for CDs.

The 1970s also saw the introduction of many other personal portable electronic devices.  These included pocket calculators, pagers, digital watches, and cell phones.  All were made possible by integrated circuits made up of thousands of transistors.  As with most things electronic, the cost of these products started high but dropped drastically as the public bought them by the millions.  

The 1980s and 1990s saw an explosion of portable personal electronics.  Everything from GPS receivers to electronic games was available from various manufacturers.  Unfortunately, most of the manufacturers were in the Far East. U.S. sources for portable electronic gear were quickly disappearing.  By 1981, the Zenith Corporation, the last U.S. radio producer, ceased production in the United States.  By the late 1990s most consumer electronics, especially the portable kind, were no longer made in the U.S.  The big exception was cellular phones.

The cellular phone situation was a little better.  The main reason for this seemed to be that the cellular technology was invented in the U.S.  By 1985 the U.S. based Motorola Corporation became the world leader in personal portable cell phones.  In 1995 Motorola contrasted their Microtac cellular phone with the first truly portable two-way radio, the BC-611 “handie-talkie” of WWII (developed by Motorola).²  Their “Razr” line became a best seller by 2003.  But, U.S. dominance in the cellular phone industry became a struggle.  By 2007 the lead in manufacture of cellular phones was taken up by European and Asian companies such as Nokia and Samsung.    

True Portable Electronic History

Technical history explains how things came about and often give hints about things to come.    Unfortunately, history in general is not a popular topic.  Military, sports, and political history sometimes merit notice, but technical history is of minor interest to most people.  Yet, it’s technical history that has shaped the last two hundred years.   

Schiffer, in his book The Portable Radio in American Life, talked about false history.  He specifically mentioned the false belief that the transistor radio was a Japanese invention.³  Much false history seems to evolve from published articles that make incorrect statements that are not recognized as such.  That sort of history can be corrected.  Forgotten history is another matter.  That seems to be the fate of portable radio technology.  Although all our modern portable electronic gadgets can trace their roots to the evolution of the vacuum tube portable radio, few people recognize the fact. 

Although most people own some type of personal electronic device most have no idea how they came about.  Amazing electronic devices are quickly taken for granted.  From satellite radio to smart phones, they all seem rather ordinary today.  Yet less than fifty years ago neither the satellite radio nor the smart phone was even imagined.   Electronic history has been forgotten.

The editors of Popular Mechanics magazine recently assembled a panel of the world's most renowned tech gurus to create a definitive list of gadgets that have changed the world.  The placed the smart phone as number one followed by radio as number two.⁴   Both smart phones and radios are electronic devices enthusiastically accepted by the public.

All of the Apple “I” devices (Ipod, Iphone, Ipad, etc.) owe their linage to the first portable radios and specifically to the personal portable radios of the early 1940s like the RCA BP-10.  In fact, it might not be too much of a stretch to say that all personal portable electronics stem from the personal portable radio.    The tree in Figure 6 shows the linage of many portable electronic devices.  The tree doesn’t show all the branches, but the general evolution of portable electronic devices should be apparent.                                                                                                

Figure 3.  A Portable Electronics Family Tree

References

1     Schiffer, Michael Brian, The Portable Radio in America, 1991, The University of Arizona                            Press Tucson & London, p223

2     http://www.gartner.com/it/page.jsp?id=612207 ,Gartner Newsroom, Egham, UK, February 27, 2008, Gartner Says Worldwide Mobile Phone Sales Increased 16 Per Cent in 2007

3   Schiffer, Michael Brian, The Portable Radio in America, 1991, The University of Arizona                              Press Tucson & London, p225

4    Popular Mechanic magazine, “101 Gadgets that have Changed the World”, http://www.popularmechanics.com/technology/gadgets/reviews/101-gadgets-that-changed-the-world#slide-1  Also: History Channel “101 Gadgets That Changed The World”  shown August 24, 2011

Emerson “Power-Mite”, the Original Pocket Radio

In the early days of radio a set that would fit in a pocket was something that sparked the imagination of a lot of people.  Of course it really wasn’t possible in the 1920s or even during most of the 1930s.  But, in 1939 RCA introduced a line of miniature tubes that could be used to design a very small radio that had good performance.    In addition to the tubes there was a need for a compact high voltage battery to power the radio.  RCA again came to the rescue in 1940 when they introduced a 67.5 Volt battery specifically designed for their compact BP-10 portable radio. 

The BP-10 was a fair to good attempt at reducing the size of the radio.  It had dimensions of 9.0” x 3.75” x 3.0”, which was pretty small for the time.  Its performance wasn’t too bad either.  The four tube superheterodyne circuit was comparable to many table top radios of that era.   Still, it was not a radio that would fit in a pocket, not even a very large coat pocket.

In the late 1920s and early 1930s several radio manufacturers tried to sell what was then known as “midget radios”.   Table model cathedral and tombstone radios were considered midget back then.  But, by 1932 midget radio manufacturers were folding almost as fast as new ones started.  An exception was the Emerson Corp.  Somehow the Emerson radios bucked the trend against midget radios.  Emerson had pioneered a radio even smaller than midget radios when they introduced the Emerson model 25 late in 1932.  That was the first of the truly compact radios.  Orders for the model 25 poured in for more than a year.  Orders were greater than production could sustain. From that point on Emerson was definitely a company the public looked to for small radios.  During subsequent years one of Emerson’s well known slogans was: “World’s Biggest Selling Little Radio.” ¹  

By 1941 several radio manufactures were producing small radios similar to RCA’s BP-10.  They were all intended for portable use in surroundings where AC power was not available.  In 1940 Emerson introduced the models 379 and 380, which were small portable sets making use of the new RCA miniature tubes.²  But, at 110 cubic inches, the 379 and 380 were not as small as the RCA BP-10.   So, not to be outdone, Emerson introduced their model 432 in 1941 and advertised it as the”Power-Mite”.  The “Power-Mite” was definitely a small radio.  In fact it was the smallest superheterodyne radio available to the public prior to WWII.³   Zenith called their small portable radio “Poketradio”, but it was much larger than the Emerson 432 and would fit in very few pockets (see table 1).

Figure 1.  The Emerson 432 “Power-Mite” could easily be held in one hand

 Figure 2.  The very crowded interior of the Emerson 432

Table 1.  Some Pre-war Personal Sized Portable Radios using Miniature Tubes⁴

Figure 3.  Although small, the Emerson 432 was just barely a pocket radio

 

The small size of the Emerson 432 required special small components, such as a variable capacitor, I.F. transformers, and speaker.  All components were crammed into 81 cubic inches with little volume left over.  The minimal remaining volume affected the acoustic performance.  The Emerson 432 sounded very tinny compared to other small portables.  But, the fact that it took up such little room somewhat made up for the poor audio quality.  

 

Figure 4.  The Emerson 432 (left) and the larger RCA BP-10 (right)

Electrically the radio used a basic four tube superheterodyne circuit similar to other radios of the period.  Other than the miniature components there were no novel electrical devices in the design.  Consequently sensitivity and selectivity were about on a par with radios like the RCA BP-10 and Motorola A1.   Some minor changes were made to the 432 design prior to WWII, but the changes did not improve the performance.  Figure 5 shows both an early and a late version.

Figure 5.  Pre-WII versions of the Emerson 432 Early (left) and late version (right)

Although the model 432 did not sell as well as the very popular RCA BP-10, Emerson did not give up on the pocket radio market.⁵ After WWII Emerson improved the design of the 432.  The improvements resulted in several Emerson models including the 508, 558, 569, 640 and other “pocket portables”.  All were basically the same size and physical layout as the pre-war Emerson 432. The physical layout pioneered by RCA, of a loop antenna in a plastic cover that could lifted to turn the radio on, was copied not only by Emerson, but by many other radio manufacturers.  That layout was essentially the most popular configuration for small portable radios until the introduction of ferrite rod antennas in the early 1950s.

Emerson followed these small tube portables with an even smaller pocket portable, the model 747.  That led to the release of a nearly identical hybrid tube/transistor model (model 856) in the mid 1950s.  After that it was transistors all the way.  The 1941 pre war model 432 was somewhat ahead of its time as a pocket set.  But, it was sincere attempt that primed the public’s interest for the true pocket portables to come.

1     http://www.antiqueradios.com/features/emerson25.html

2   Radio and Television Retailing Magazine, McGraw Hill Publishing Co., August 1940, p38, Advertisement for the Emerson model 379 radio)

3   Schiffer, Michael Brian, The Portable Radio in America, 1991, The University of Arizona   
     Press Tucson & London, p124

4     Radiomuseum (website),  http://www.radiomuseum.org/act_main.cfm, radio listings using 1S4  and 3S4 vacuum tubes (1940- 1941

5     Warnagiris, T., “Radio Wherever I go”, Antique Radio Classified, February 2011, Vol. 28, No. 2,   p11