Where did all this stuff come from?

Today we have smart phones, tablets, MP3 players, and lots of other portable electronic devices too numerous to name.  A few years ago we also had pagers, personal data assistants, portable CD players and others.  It would seem that all these portable marvels must have originated with the ubiquitous transistor radio of the 1950s.  But, that’s not exactly correct.  It really started much earlier.  As far back as the early 1920s some speculators suggested that a portable radio might be possible.  It  was possible and happened quickly.  In 1924 Zenith introduced the first fully contained (radio, batteries, antenna, and speaker) portable radio.  It was suitcase sized, but it was portable.  In 1925 the Radio Corporation of America (RCA) offered their portable model 24 Radiola and Westinghouse and others followed with similar self contained portable radios.  Thes portable frenzy did not last long. 

All of the first generation portables were expensive compared to their non-portable brethren.   They also were heavy.  Battery consumption was high and they were very bulky, too bulky to carry and play.  Some improvements came with time, but public interest waned.  Slowly but surely the number of portable radios sold dropped year by year.  So, that by 1937 not a single major radio manufacturer offered a battery operated portable radio.   

There was still a market for portable radios.  But, it was apparent that the radio buying public wanted improvements in battery life, weight, and reliability.  That didn’t happen until 1938.  That year Sylvania introduced a new line of low power tubes.  Less costly batteries also became available.  The result was a portable radio renaissance.  By late 1939 just about every significant radio manufacturer was offering a portable radio.  But they were still big.  Most were still the size of a small suitcase.  To offer something more compact required further reduction in the size of tubes, batteries and other radio parts.  Fortunately that didn’t take long.

In 1939 RCA introduced a line of miniature tubes and compact batteries to power them.  This led to the small personal portable radios available prior to WWII.  RCA’s model BP-10 set the standard.  Others copied the idea.  The figure below shows an RCA BP-10 with several prewar personal sets from other manufactures.   Although popular at the time, they were still not very good on battery life, size and reliability.  Until the invention of the transistor they were about as small and portable as a radio could get.  Unfortunately, WWII stopped the production of all radios for civilian use.   The three year war hiatus cooled the public interest in personal sets.  After the war RCA, Emerson, and a few others tried to market battery portables, but they didn’t sell well unless they could also operate from house current. 

In 1954 a small company called Regency offered a transistor radio just in time for the Christmas sales season.  Although it was not a great radio it sold well and sparked a revival of public interest in radios that could be played while carried, i.e. personal portables.  As they say, the rest is history.  After transistor radios there were portable tape players, pagers, calculators, leading to all the modern portable devices we now can’t do without.

 

Personal Portable Electronics: The Beginning

Personal Portable Electronics: The Beginning

It’s not difficult to pinpoint the time period when personal electronics first appeared.  It happened just prior to WWII.  Before then electronics consisted only of radios and phonographs neither of which was either very personal or portable.  By 1938 it was possible to build radios that could be carried and used as a personal set, but few manufacturers were selling them.  Magazines such as Popular Science and Popular Mechanics featured several “build it yourself” articles for those wishing to have a radio primarily for use by one person.  Radio manufactures pretty much ignored the idea.

In 1938 the new low power radio tubes supplied by the Sylvania Corp. allowed most radio manufacturers the opportunity to design personal radios.  Very few did.  One of the few was the Majestic Radio Company.  In 1939 they built, advertised, and sold a very small (for the time) radio that could be carried on the shoulder like a purse.  It used three low power tubes and was self contained (radio, battery, antenna, and speaker in one unit).   No one could argue that the radio was anything other than a personal radio.

Majestic advertised the radio as similar to a camera, which at that time most people understood as a small box handing from a shoulder strap.  The camera comparison was copied by a number of competitors including RCA, DeWald, Admiral, and General Electric.  By 1940 these radio manufactures and many others were producing and selling “camera style Personal Radios”.  Many of these personal sets were battery powered and intended for use by one person often while walking.  Thus personal portable electronics was born. 

Since their cases were made of pressed cardboard few, 1939 Majestic “Personal Radios” survived.

Public Perception of the BP-10 Personal Radio

In the late 1930s radio sales were primarily for table top and floor console radios in fine wood veneer cabinets.  They were pieces of furniture as much as they were entertainment devices.  Cheaper sets in plastic were available, but they were considered inferior even though almost all of the sets sold could be plugged into the wall.  A few could be run from batteries, but those were primarily for the “farm market”.  Most farms back then had no electricity.  So, when RCA introduced the BP-10 personal portable radio in 1940 it met some resistance from radio salesmen.  It was not in a pretty wood cabinet and it did not plug into the wall.  The price was also higher than some of the cheaper small radios that could be plugged in, but too cheap to be profitable to the radio salesman. 

A battery only radio was somewhat of a novelty in 1940.  A few battery only sets had been introduced in 1939.  But, those were large “luggable” sets designed primarily to be taken from place to place not played in transit.   In fact the manufactures of the 1939 radio covered their radio cabinets in so called “airplane fabric”.  This was the same fabric used to cover travel suit cases of that era.

With all that considered it was anyone’s guess as to how the public would react to the BP-10 radio.  RCA’s David Sarnoff (CEO) was confident that a true “on the go” small portable would be a hit with the public.  The rest of RCA was not so sure.  Nevertheless, RCA pulled out all the stops promoting the new BP-10 Personal Portable radio.  The BP-10 was advertized in magazines, newspapers, movies, and just about every other way possible in 1940.  Public acceptance was dramatic.  With over 200,000 sold in less than a year the BP-10 was one of the most recognizable radios of the era.  The radio was so successful that the art deco black and chrome look was copied by Emerson, Motorola, Westinghouse, and other radio manufacturers.  In fact the black and chrome look persisted right up through the transistor radio craze.

 

The original black and chrome 1940 BP-10 radio on the right with a 1962 Silvertone transistor radio on the left.

The History of Personal Portable Electronics

New technologies and the science behind them have become very important in people’s lives while at the same time being entirely incomprehensible to all but a few.  And, the personal portable technologies are among the most incomprehensible.  Smart phones, GPS, and digital cameras are just a few personal portables that most people have no idea how they work, yet they rely on them to work when they want them to.  If they don’t they discard them and replace them with the latest model.

Now a flashlight is a relatively simple electrical device.  Despite its simplicity its invention didn’t occur until around 1900.  Conrad Hubert received a US patent for the flashlight in 1903.  The invention depended upon earlier inventions of the compact battery and miniature electric light.  Since it was designed for one person and was portable it might be acknowledged as the first personal portable electrical device.  It was unquestionably a useful invention and was the precursor of more complex portable electrical devices.  

It took another twenty years before a second battery operated portable device was marketed to the public.  The device was radio.  David Sarnoff, the head of the Radio Corporation of America (RCA), was a staunch propagator of the personal portable radio.  As early as 1922, he was credited with proposing a portable radio.   As head of RCA he was instrumental in marketing a series of portable radios in the mid1920s.  Unfortunately, they were expensive, heavy, and ahead of their time.  And, like today’s smart phones and handheld GPS devices, how the radio worked was a mystery to most people at the time.  Like the simple flashlight the truly personal portable radio had to wait for the invention of miniature components and efficient batteries. 

Those inventions finally came along in 1938.  That year RCA introduced a line of new compact vacuum tubes and an improved battery to power them.  The first RCA product using the new tubes was the BP-10 Personal Portable Radio.  In 1939 the smallest full featured portable radio was the Majestic model 130.  It was a three tube radio using conventional, tubes for that time.  In 1939 RCA was also selling portable radios, but their radios were much larger. 

Then in 1940 the new RCA tubes were used by a number of radio companies to produce radios almost small enough to fit it a very large pocket.  Emerson, Admiral, Westinghouse, and several others recognized the public’s desire for a radio they could carry while in use.  The 1940 offerings were a start, but still not enough of a good thing.  The war intervened and after the war the prewar radio designs were updated and again offered to the public with limited success. 

The 1940 RCA Personal Radio on the left and a 1956 RCA Transistor Radio with a flashlight battery shown for scale

Again, new inventions were needed to bring the next big personal portable device.  It was again radio, a transistor radio.  The invention of the transistor in 1947 sparked the most significant improvement in battery operated portable devices.  Transistor radios, walkie talkies, and tape recorders were all made truly portable and in some cases, pocket sized by 1960.  Then things got interesting when the portable devices became digital.  That started around 1970 with the introduction of pocket calculators and digital watches.  The digitization of portable devices made some portable devices programmable.  That quickly started with programmable hand held calculators in 1971.  From there the number and types of personal portable devices exploded.  Programmable Digital Assistants (PDAs), MP3 players, cellular phones, and hand held computers were gobbled up by the using public.  Still, only a few understood how they worked and the science behind them.

Then a funny thing happened.  The users were learning to “customize” these portable devices.  Since most incorporated a digital processor they could be programmed not only by the manufacturer, but by the user as well.  The personal portable electronics were becoming truly personal.  Even the most casual user of the new portable devices began to add, delete, and change the way their personal device operated.  It could be as simple as changing the ring tone of a cellular phone or as complex as reprogramming a hand held computer.  At a minimum the users were now truly interactive with their personal portable devices.  And, they were now learning how to change the functionality of their devices by changing the software.  The users understood the software or at least the programming aspect.  There was no need to understand how the digital device worked.  The hardware and the science behind it were still a mystery, but the users were truly interactive with their devices and many learned how to make their devices do what they wanted by programming.  User generated software became as complex as the hardware.  The public was no longer ignorant of what mattered with their personal portable devices.  The programming mattered and that’s what the users understood and all that the users needed to understand.

Strangely, a flashlight is interactive in that the user points the flashlight where wanted, while more complex portable devices like radios, televisions, and MP3 players are essentially passive, that is non interactive.  It’s only the digital personal portable devices along with the simple flashlight that are truly interactive.

On D-day was the BC-611 a cell phone?

Of course there were no cell phones on the D-day beachhead.  That June 6^th of 1944 was thirty years too early to benefit from cellular technology.  But, some of the technology available on D day was definitely the predecessor to today’s cell phones.  Specifically, the battery operated hand held BC-611 two way radios  known as handie talkies (not walkie talkies, they were back pack sets).  The handie talkies were essentially vacuum tube versions of basic cell phone technology that could be held in one hand.  

To make the BC-611 certain technological improvements were needed.The personal portable electronics revolution started in 1939 with RCA’s development of miniature vacuum tubes.   By mid 1940 a series of portable radios using the new tubes was available to the public.  Radios were then small enough to be listened to while being carried.   From this “on the go” use of radios Motorola engineer Donald Mitchell recognized the potential military value of portable communications.  In 1940 he observed a National Guard exercise and saw how existing military radios were neither mobile nor effective.  He became convinced that military communications had to be man portable and immediately began to design a radio to meet the need.

He and his team developed a two-way AM radio that a single person could carry and operate with one hand.  It was tuned to a particular channel using sets of crystals.  It was battery-powered and weighed just 5 pounds (2.2 kg). The resulting two-way radio was the Handie-Talkie, or BC-611, the Signal Corps model number, saw action in every theater of war, with nearly 40,000 built for the various services.  Motorola went into full production in July of 1941, six months before Pearl Harbor

Although portable two-way radios existed prior to 1941, none were compact enough to hold in one hand.  That feature, along with the earphone and microphone spaced as in a conventional telephone, were the key differences between the Handie-Talkie and other “walkie--talkies” of the WWII era.  Although these features seem minor, in retrospect the combined features were the key to the truly wireless phone concept.  Like the Willys Jeep the BC-611 was a memorable and iconic product of WWII.   In 1995 a Motorola advertisement credited the BC-611 as being the “grandfather” of the cellular phone.

  The BC-611 Handie-Talkie in action

 Today there is some confusion as to what constitutes a “walkie-talkie”.  During WWII “walkie-talkies” were any man portable two-way radio capable of being used while walking.  Most such radios were pack sets designed to be carried on the back or in some cases on the chest of the radio operator.

Donald Lewes Hings, a Canadian, designed the first portable pack set that led to the walkie-talkies of World War II.   His pack sets were initially developed in the 1930s for mining applications.  The pack sets were not called “walkie-talkies” at the time. They were simply called portable two-way radios or wireless sets.  The term “walkie-talkie" was coined by journalists describing radios of this type used during the war.  Hings' developed a variety of portable two-way radios for the Canadian army including the C-58 Pack Set. The Model C-58 was a very successful design, both in performance and production, with tens of thousands built.  

Alfred J. Gross a.k.a. Irving J. Gross was another early designer of portable two-way radios.  He was born in Toronto, Canada in 1918, but grew up and was educated in the United States.   Soon after the invention of the “walkie-talkie” by Donald Hings, in 1937 Al Gross designed, built, and patented his own version of the “walkie-talkie”.  This led to his involvement in building a two-way air-to-ground communications system for the U.S. Office of Strategic Services (OSS) for use in military operations, known as the Joan-Eleanor system.  It consisted of a hand-held two-way radio ("Joan") and a much larger aircraft-based two-way radio ("Eleanor"). It was classified Top Secret by the U.S. military until it was declassified in 1976.

Other “walkie-talkies” were used during the war by other nations. The British, Germans, Japanese, and Canadians had their own portable two-way radio designs. Since these various radios used different circuits, they were often developed independently with each making claims of being the first of its kind. There were many differences in the performance and portability of these various designs; however none was similar to a hand held wireless telephone like the Handie-Talkie.

For example, the AN/CRC-7, was the first hand -held VHF AM downed airman's radio.  It was somewhat like a Handie-Talkie in that it could be held in one hand.  But, it had a combination speaker/microphone that changed function when the receive or transmit button was pushed.  It was not like a telephone in appearance or operation (see: http://www.qsl.net/g4bxd/crc7.jpg). 

The BC-222/322 (SCR-194/195) along with the TBY were other early “walkie-talkies” designed by the Army and Navy laboratories.  They were pack radios, and as such designed to be operable while in motion on the operator's back or chest.  Although for these particular radios operation while in motion would result in erratic operation.  Operation at a stationary location was the norm.

The U.S. Navy MAB was a typical chest mounted “walkie-talkie” used during WWII.  It was actually designed prior to the Handie-Talkie for use by Marine paratroops. The Navy MAB was typical of most WWII “walkie--talkies” in that it had a microphone, headset, and antenna, separate from the radio.

The Navy MAB “walkie-talkie” shown with most of its accessories.

One Handie-Talkie feature that was not like a telephone was the need to press a button to switch from receiving to sending.  Most two-way radios to that point in time required such button pushing.  Of course, a cell phone does not.  There were ways to allow simultaneous sending and receiving during WWII, but they were complicated and not amenable to portable equipment.  It wasn’t until the 1970’s that practical simultaneous sending and receiving made the “Handie- Talkie” concept into a true wireless telephone.  The first wireless telephone conversation took place in 1973, but it wasn’t until 1983 that hand held wireless or in this case cellular telephones were available to the public.

 

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