Zenith Model 4-V-31 Tombstone Farm Radio (1936)
This 1936 tombstone-style radio is designed to
operate from a 6V lead-acid battery. Many rural
locations back in 1936, especially farms, were
not connected to the electricity supply and as a
result there was quite a niche market for these
so-called "farm" radios. This set covered the
standard broadcast band from 500-1800kc* and
used 4 tubes. The tube line-up is 15 (LO/mixer),
15 (IF), 75 (2nd detector/AGC/1st AF), 38 (AF
Output).
At the heart of its power-supply, this set uses a
device called a vibrator to convert the DC
current from the battery to AC, whereupon it is
stepped-up in voltage, rectified and smoothed to
provide the B+ supply. The filaments in this set
are supplied directly from the 6V battery.
I don't usually collect Farm radios, but they are
an important part of American radio history and I
believe every collection should have at least
one. This model is just so pleasing to the eye
and like so many of the Zeniths, it has become so
very collectible.
* The Ryders schematic for this model is incorrect,
calling out 500-1700kc.
operate from a 6V lead-acid battery. Many rural
locations back in 1936, especially farms, were
not connected to the electricity supply and as a
result there was quite a niche market for these
so-called "farm" radios. This set covered the
standard broadcast band from 500-1800kc* and
used 4 tubes. The tube line-up is 15 (LO/mixer),
15 (IF), 75 (2nd detector/AGC/1st AF), 38 (AF
Output).
At the heart of its power-supply, this set uses a
device called a vibrator to convert the DC
current from the battery to AC, whereupon it is
stepped-up in voltage, rectified and smoothed to
provide the B+ supply. The filaments in this set
are supplied directly from the 6V battery.
I don't usually collect Farm radios, but they are
an important part of American radio history and I
believe every collection should have at least
one. This model is just so pleasing to the eye
and like so many of the Zeniths, it has become so
very collectible.
* The Ryders schematic for this model is incorrect,
calling out 500-1700kc.
Zenith and Farm Radios
In the early days, prior to the widespread electrification of homes, tube radios used expensive and bulky A, B and C batteries, some
of which needed to be constantly recharged or replaced. The frequent handling of these batteries meant that acid spills were
common, ruining furnishings and floorings. As a result, many radios ended up largely unused. Something had to be done!
By the mid twenties, with the advent of more widespread electrification, the first solution to this problem arrived in the form of battery
eliminator units. These were separate from the radio and designed to plug into light sockets. A great improvement! By the time 1927
came around, millions of such units had been sold. However, at that time tubes designed for AC filament operation appeared and
radios having built-in power supplies, designed to be plugged directly into a light socket, became available. Overnight, the old battery
radios, batteries and battery eliminators were rendered almost (but not quite) obsolete. Dealers and manufacturers arranged "radio
burning" parties in public places, encouraging the public to dispose of their old radios and replace them with the latest
socket-powered models.
This was all possible except in remote rural areas, which because of the high cost of stringing power lines were the last to be
connected to the power grids. As a result, battery sets continued to be used in these areas, even as late as 1950. However, largely
because of the entrepreneurship of the Zenith Corporation, all was not as bad in these communities as it might first appear.
Sometime in the early 30s, the vibrator or chopper tube was invented, probably driven by the burgeoning demand for automobile
radios. This was a mechanical device that would rapidly reverse the polarity of a DC battery supply and generate an alternating
voltage that could be applied to a transformer, which in conjunction with a rectifier tube produced all the internal voltages required by
a radio. This meant that a single low voltage battery was all that was needed to operate a set. Even though a beefy automobile
battery was used, it would nevertheless need periodic re-charging, usually necessitating a trip to the local auto shop (where there
was power). This whole process could sometimes take several days and since the batteries were expensive, back-ups were often
unavailable. Soon, however, small wind-driven electric generators began to be used to re-charge batteries when the radio (or other
device) was not in use. Commander McDonald of Zenith was early in recognizing the economics of these "Winchargers" and bought
a majority share in a small company producing them. He introduced mass-production techniques and clever marketing, offering
discounts on "Zenith Winchargers" with every Zenith farm radio bought (& even with radios of other manufacturers). Soon thousands
of the small windmills were being sold a month at prices as low as $10 - $20, establishing Zenith as the radio of choice for rural
America.
In the early days, prior to the widespread electrification of homes, tube radios used expensive and bulky A, B and C batteries, some
of which needed to be constantly recharged or replaced. The frequent handling of these batteries meant that acid spills were
common, ruining furnishings and floorings. As a result, many radios ended up largely unused. Something had to be done!
By the mid twenties, with the advent of more widespread electrification, the first solution to this problem arrived in the form of battery
eliminator units. These were separate from the radio and designed to plug into light sockets. A great improvement! By the time 1927
came around, millions of such units had been sold. However, at that time tubes designed for AC filament operation appeared and
radios having built-in power supplies, designed to be plugged directly into a light socket, became available. Overnight, the old battery
radios, batteries and battery eliminators were rendered almost (but not quite) obsolete. Dealers and manufacturers arranged "radio
burning" parties in public places, encouraging the public to dispose of their old radios and replace them with the latest
socket-powered models.
This was all possible except in remote rural areas, which because of the high cost of stringing power lines were the last to be
connected to the power grids. As a result, battery sets continued to be used in these areas, even as late as 1950. However, largely
because of the entrepreneurship of the Zenith Corporation, all was not as bad in these communities as it might first appear.
Sometime in the early 30s, the vibrator or chopper tube was invented, probably driven by the burgeoning demand for automobile
radios. This was a mechanical device that would rapidly reverse the polarity of a DC battery supply and generate an alternating
voltage that could be applied to a transformer, which in conjunction with a rectifier tube produced all the internal voltages required by
a radio. This meant that a single low voltage battery was all that was needed to operate a set. Even though a beefy automobile
battery was used, it would nevertheless need periodic re-charging, usually necessitating a trip to the local auto shop (where there
was power). This whole process could sometimes take several days and since the batteries were expensive, back-ups were often
unavailable. Soon, however, small wind-driven electric generators began to be used to re-charge batteries when the radio (or other
device) was not in use. Commander McDonald of Zenith was early in recognizing the economics of these "Winchargers" and bought
a majority share in a small company producing them. He introduced mass-production techniques and clever marketing, offering
discounts on "Zenith Winchargers" with every Zenith farm radio bought (& even with radios of other manufacturers). Soon thousands
of the small windmills were being sold a month at prices as low as $10 - $20, establishing Zenith as the radio of choice for rural
America.
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