Radiola Senior Regenerative Receiver
- Type RF
Radiola A.C. 2
Stage Audio Amplifier - Type AC
The very popular, single tube receiver, Aeriola Senior,
was introduced in late 1921 for $65. By late 1922, it had been updated with a bakelite panel and
mahogany box. Still later, in 1923, the name was changed to Radiola Senior
(price was still $65.)
A two-stage AF amplifier was an accessory to the Aeriola Sr. and also to
the later Radiola Sr., also priced at $65. The 2-Stage Audio Amplifier added enough audio gain that a
horn speaker could be used on most of the stronger signals, thus
allowing the entire family to enjoy "the radio." The Aeriola and Radiola
single tube, regenerative receivers perform quite well and are easy to operate requiring
only a single 1.5vdc dry cell and a 22.5vdc B+ battery, a set of earphones and a suitable
antenna and ground. The tube normally used is a WD-11, however an 864 or WE239A will work
equally well but will require the use of a socket adapter (WE-239A is
shown installed.) The AF
Amplifier requires two WD-11 (or compatible substitutes) along with a
set of dry cells for the filaments and a 60 to 90vdc B+ battery. The
amplifier is shown with later type WD-11 tubes installed. The
horn speaker was optional.
Telephone and Telegraph Co.
Federal built high quality receivers though some of their circuits and
mechanical devices seem rather "Rube Goldberg" at times. The DX Type-58,
from late 1922, was designed for the enthusiast and the metal cabinet
seems to show this. Selling price was somewhat expensive for a four tube
set - $123. Federal's workmanship was excellent, however their
documentation is vague at best. It
is interesting that Federal was so afraid of a RCA-Westinghouse law suit over the
Regenerative Detector patent, they didn't tell owners (in their instruction manuals) that
their radios could be set to regenerate and therefore significantly increase performance.
Having "Regeneration" in print in an operator's manual would have been
as good as an admission of guilt by Federal. Most owners figured out the
adjustments anyway and the radios were fairly popular. By setting the "COUP" control to near "0" and advancing the
"AMP" control to near the oscillation point, the DX Type-58 (and most other
Federals) can be quite sensitive and selective receivers.
Federal Telephone & Telegraph Co.
Introduced in the fall of 1923, the Type 61 was Federal's
high-end receiver, selling for an incredible $223. The circuit used six tubes - three RF
amplifiers with grid-bias controlled amplification running into the detector stage and two
transformer coupled audio amplifiers. One could select either one RF stage or three RF
stages, a loop antenna input or external antenna input. One could also select various
audio amplification circuits and the second audio interstage transformer has a selectable
ratio secondary. In all, sixteen different configurations could be set-up, making the
Federal 61 one of the most versatile battery receivers of its day. Though the manual is
vague about the regenerative capabilities of the Type 61 ("regeneration" is
never mentioned), performance can be excellent if the "COUPLING" is kept near
minimum and the "RF AMPLIFICATION CONTROL" set near the oscillation point.
(Tri-City Electrical Supply Company) for Montgomery-Ward
built for TRESCO by BRIGGS &
Briggs & Stratton building radios? That's right.
Montgomery-Ward had contracted with TRESCO to build the 1923 Super
Airline regenerative receivers they were going to sell out of their
catalog. Demand for radios in 1923 was just about at its peak with
the "Radio Boom" having most manufacturers putting on extra shifts
and hiring more workers to keep up with orders. The demand for the
Super Airline was too much for TRESCO to handle but rather than
expand the company (which they probably knew was not the right
business decision) they sub-contracted some of their assembly work
out to Briggs & Stratton, a small-engine building company that
was located in the same area. The Briggs & Stratton Super Airline
receivers look just like those built by TRESCO. So how do you tell
them apart? Fortunately, Briggs & Stratton applied decals with their
company name on the back of the three tube sockets. Of course, I
used to tell museum visitors that you could tell the Briggs &
Stratton versions by the "pull rope" on the back of the radio.
The Super Airline is a three tube regenerative
receiver using 1A pure tungsten tubes - one UV-200 soft detector and
two UV-201 hard amplifier tubes were used. The tuner is a two circuit
type (fixed coupling) and it's not particularly selective.
Model 4560 - 1924
- a.k.a. 10-B, "A-K Breadboard"
TA - 2 STAGE AF AMPLIFIER
Arthur Atwater-Kent made a fortune
in the automotive ignition and lighting business but moved into radio parts manufacturing
around 1922. Initially, A-K offered various kinds of radio parts to
build your own receiver. By 1923, complete A-K radios were being offered. Shown is the 1924,
Model 4560 (A-K 10-B) in standard finish, (black paint on the cans.) A-K
believed his manufactured parts were beautiful (and so do a lot of
collectors) so exposing them on open boards seemed the logical design
for his receivers. Original selling
price for the A-K breadboards was usually around $100. The TRF circuit
provided good reception although the upper limit of the tuning was about
1200kc. Quality was top notch, as with all A-K receivers. There are many
variations and different models of breadboard sets that were made between 1923 and 1925.
Shown in the photo to the right is one of Atwater-Kent's component
parts that were being sold in 1922 and 1923. This is a two-stage,
transformer coupled audio amplifier. Connections are via binding
posts behind the tube sockets. The potentiometer adjusts the
filament voltage on both tubes as a method to control gain or output
level. Although the intended tubes were probably UV-201A tubes, this
TA was found with two good condition WD-12 tubes installed. Early
A-K cans were painted an olive-green color and some of the very
early breadboard sets also have cans with this color paint applied.
All of the later cans are either black or brown wrinkle finish
General Electric for RCA
AR-812 Second Harmonic
The AR-812 was the first production superheterodyne
offered to the general public. Western Electric was producing
commercial superheterodynes earlier and supposedly installed one in
the White House. That "fired up" David Sarnoff, who
was RCA's GM at the time, to have GE build a superhet for RCA to
sell. As with many new types of circuits, the AR-812 prototypes
didn't work very well with internally generated
noise due to reflexing some of the circuits. Ed Armstrong was called
in as a consultant and the problems were reduced to the
point where the receiver could be offered for sale. RCA was aiming for
Christmas 1923 but delays moved the release date to February 1924. The
incredibly high selling price of $235 didn't seem to deter the radio
enthusiasts and the AR-812 sold very well. It sold even better when
the price was reduced and, by 1925, new-in-the-box, surplus production
left-overs, were being sold for $10. The AR-812 did out-perform most
of the competition and with a large indoor loop antenna, coast-to-coast
reception was possible. Six UV-199 tubes are used and the receiver
does have have a small built-in antenna. In fact, some of the
advertising for the AR-812 promoted the receiver as being
The AR-812 uses what RCA called
"catacomb" construction. Most of the receiver circuitry and
components were contained in a metal box that is filled with hard
wax. The external flexible wire connections were called "whiskers"
for some reason. It is possible to determine faults in a catacomb by
measuring the resistance between various whiskers. RCA provided the
data and procedure for testing catacombs. However, RCA wanted the
defective catacombs returned or exchanged for good ones when doing
repairs. Not possible today, of course, and most restorers repair
their own catacombs (if they want the receiver to function.) I use a
second-hand toaster oven (usually a few dollars at thrift stores)
set to 180F or so to melt out the wax. It will be necessary to
carefully remove the lead seals to preserve the embossed "RCA" on
them. Also, sometimes a vent hole has to be drilled to allow the
heated wax to flow out. Once the wax is removed, repair is straight
forward. You'll almost certainly find that some of the very fine wires
used in the circuit have broken. This is probably due to expansion
of the wax breaking the fine wires. Once the catacomb is repaired,
you don't need to refill it with wax again. RCA used the wax as a
method of keeping the superheterodyne construction secret or at
least from becoming common knowledge to the technoids of the time.
The AR-812 shown in the photo was found (in 1993) in
the upstairs storage rooms above the Crystal Bar in Virginia City,
Nevada. The Kolster Loop Antenna (Federal Telegraph Company) and the
RCA UZ-1325 horn-speaker were with the
AR-812 and the radio had all six 1.5vdc dry cells still installed.
The "station cards" are vintage and were penciled in with west coast
stations. In the past, the radio had been operated using dry cells
for the filaments and an AC operated "B eliminator" for the higher voltages. Just
how long the radio, loop and horn had been upstairs is hard to say.
Bill Marks, who owned the Crystal Bar then, was an avid collector of
all kinds of antiques. The Crystal Bar was famous for its display of various kinds of orchestrons,
nickelodeons and other types of mechanical music players. The
upstairs was filled with other types of antiques including phonographs, radios and
parts. Everything was eventually sold off when the Marks died. The
Crystal Bar is now the Visitor's Center for Virginia City operated
by the VCCTA.
Powel Crosley Jr. got into the radio business
because his son wanted a crystal set. The prices were too expensive, in Crosley's opinion,
so he bought a twenty-five cent booklet instead and built his first radio.
Realizing how easy it would be to build and sell simple receivers, Crosley bought Precision Electric
(in 1922) to begin his radio business and the following year
formed Crosley Radio Corporation from Precision Electric. Crosley radios
are noted for
good performance with inexpensive parts and cabinets. By keeping
manufacturing costs low, Crosley was able to offer his radios at very
low prices resulting in high sales. His methods of manufacture eventually
led to his becoming known as
the "Henry Ford of Radio." Crosley went on to owning BC
station WLW, owning the Cincinnati Red Legs baseball team, building
small cars and many other endeavors. Shown is a 1924 Crosley XJ, a four tube TRF
One of the most common Crosley battery operated regenerative
receivers is the Model 51. Crosley sold them for $25 and the little
two-tube radio performed quite well. Certainly, the Model 51 shows
what can be accomplished when the goal is to build a two-tuber
(regenerative detector and one stage of AF amplification) as
economically as possible. Crosley was already famous for their
ultra-simple "book condenser" that replaced the expensive tuning
condenser. The "tickler" was a push-in or pull-out type of control that
allowed the operator to control regeneration by changing the
proximity of the tickler coil to the secondary coil. A simple push
or pull of the regeneration knob changed the position of the tickler coil behind
the panel to adjust the regenerative feedback. Most of the other parts used in construction are standard
for the period. The cabinet is made out of poplar wood and was given
a very basic finish (probably just a coat of shellac.) It didn't
matter how cheaply made the Model 51 was - it performed quite well, better
than many other more expensive sets. Crosley sold thousands of the
Model 51 for that very reason. The Model 51 was available from 1924
through early-1925. The Model 51 shown still has its complete original
warranty card attached under the lid. The date on the card is
interesting, Dec.25, 1924 - Christmas Day. This 51 is in "as found"
R. E. Thompson Mfg. Co.
The Thompson Grandette - V-50
Roy E. Thompson worked in the Department of
Commerce, then for Kilbourne & Clark before buying Wireless
Improvement Company around 1917. He started R. E. Thompson Mfg. Co.
to obtain a Neutrodyne license from the Independent Radio
Manufacturers. The "Independent
Radio Manufacturers" was formed by eleven companies who wanted to develop a
radio that could compete with the GE-RCA-Westinghouse owned Superheterodynes. They approached Louis Hazeltine for the design work
and the Neutrodyne was born. It used capacitive feedback in the RF
amplifiers to cancel the tube's interelectrode capacitance which then
allowed for higher gain in that stage without oscillation instability. The Neutrodyne, when properly designed and manufactured was the best
performing TRF radio receiver of the time. While it didn't always
perform as well as a Superheterodyne, it certainly performed better
than any other type of TRF receiver. Unfortunately for all other manufacturers,
unless you were an original "Independent Radio Manufacturer", you couldn't
legally build Neutrodynes (see "Grebe MU-1" below.)
The Thompson V-50
was introduced in October 1924. It is a well-built Neutrodyne using
five tubes that consisted of two Neutrodyne RF amplifiers, Detector
and two stages of audio amplification. Interestingly, the V-50
allows the option of either using the C- bias or not, all controlled
by connecting or disconnecting a metal strap across the bias battery
connection terminals. At the time, the only reason for using C- bias
in the audio section was to prolong the life of the B+ batteries.
Also, a "dummy plug" is installed in one of two chassis jacks marked
"1" or "2" to select whether one or two audio stages are used for
the output jack on the front panel. The Grandette V-50 styling is typical of the 1923-24 Neutrodynes,
that is, black panels and three symmetrically mounted tuning dials.
Inside the workmanship is first-class. Thompson also sold a matching
horn speaker that featured a direct-driven conical diaphragm.
were high priced with the V-50 selling for $125 in 1924. Thompson
radios looked like the typical Neutrodyne (the early FADA.) A few other
manufacturers had models out there at half the cost of Thompson's
least expensive models. Those cheap radios weren't Neutrodynes but
most radio consumers didn't know the difference and were only
concerned with the price of their intended purchase. Take a look at
the early Freshman Masterpiece (which actually came out before the
V-50) as an example of a radio that looked
convincingly like the typical Neutrodyne but sold for only $60 (Freshman
write-up below.) To the
radio-buying public, the Freshman was the better deal - until they
got it home and found out how badly it performed. The Thompson V-50 would
easily "bury" the Freshman in all areas of performance. Unfortunately, the
new Freshman owners found out too late that they had
been "taken" by Charlie Freshman.
Thompson's sales were never as high as expected and
the company was in constant debt, despite introducing new models. By
the end of 1927, Thompson was out of business. Interestingly,
Charlie Freshman was also about to be forced out of his company. The
days of selling "really cheap" radios were about to end with the introduction
of lightsocket-powered radios - AC-operated in most areas,
DC-operated in Edison-powered areas (rural areas still had to stick
with battery operation.) Even a merger with Freed-Eisemann
didn't help Freshman since the 1929 Stock Market Crash was right around the corner.
Chas. Freshman Company
Freshman Masterpiece &
Charlie Freshman entered the radio business
at the right time, made a lot of money and then got out of
the business to spend that money. Starting in 1922, Freshman
began selling radio parts and then moved into fully
assembled radios when the Neutrodynes started coming out
(late-1923 for the FADA.) Designed to look like the typical
Neutrodyne, Freshman's radio, the Masterpiece, sold for half
the price at $60. If you wanted it as a kit, the cost was
only $17. Freshman's engineers utilized the losses of
mounting the RF stage inductance directly onto the metal frame of the
tuning condensers to prevent the RF amplifier stages from oscillating.
This was Freshman's approach, build as cheaply as possible.
It worked, too. At its production height, Freshman was
turning out over 1000 radios a day. Only after the novice
radio buyer got a chance to listen to a neighbor's real
Neutrodyne radio did he
then realize how badly the Freshman Masterpiece performed.
Reliability was also an issue with Freshman Masterpiece
radios with defective interstage transformers and
potentiometers being the worst offenders. As Freshman
evolved as a business, his radios really didn't. New
cabinets and different tuning dials maybe, but the circuits
remained basically unchanged. >>>
||>>> Freshman used a particularly high ratio
interstage transformer that was not only unreliable but even when
working provided so much gain that the audio distorted
heavily. Most of the transformers used 6:1 ratio or even
higher while the industry standard was 3:1. By 1928, Charlie
Freshman was forced out of the company and Walter Chrysler
infused some cash into a merger of Freshman and the
Freed-Eisemann Company. While the Freed-Eisemann name was
used for the high-priced models, EARL was used for the
Freshman models. EARL lasted a year or so, until late-1929
brought on the Stock Market Crash.
Freshman made a lot of
radios. While they are very common, it is rare to find one
that hasn't had some repairs made to it. After all, the
parts were just about the cheapest that Charlie could find.
The upper photo shows the typical 1924 Freshman Masterpiece.
Supposedly, if the "Freshman Masterpiece" logo isn't present
under the switch, then that particular set was the kit
version. I've only seen one FM without the logo, so not too
many buyers opt'd for the kit.
Shown to the left is the later version of the 5-F-4
model. Earlier versions had external dials while the later
version have the dials behind the small windows. This model
sold for $49 - really cheap. What is unusual about this
particular 5-F-4 is that it is all original and functional.
The distortion from the audio is unbelievable due to the 8:1
ratio interstage transformers with no -C bias. Even one of
the contemporary radio magazines stated that Freshman's
business relied on inexperienced buyers that eventually
learned that they had been "taken" by Charlie.
AMRAD was the
American Radio and Research Corporation. Though founded with J. P.
Morgan money, Morgan's son ran the company after his father's death in
1913. AMRAD never seemed to be on the "cutting edge" of radio and,
despite a lot of money, AMRAD was always a "technologically backwards"
company. It was just luck that they became one of the original members of the
Manufacturers" and was licensed to produce Hazeltine-Neutrodyne
receivers in 1923. However, in an amazingly incompetent decision, AMRAD didn't offer their Neutrodyne
receiver immediately and delayed the introduction
until the Christmas season of 1924. The decision to delay their
Neutrodyne cost AMRAD thousands of potential sales and the company lost a tremendous
amount of money and respect. Within six months AMRAD was bankrupt.
Neutrodyne is somewhat different that the normal layout with one
Neutrodyne RF amplifier, Detector and three stages of audio
amplification. AMRAD also decided to build the receiver very
compactly resulting in one of the smallest of the 1924 Neutrodyne
radio receivers. The Neutrodyne was the last model AMRAD produced before the
company went bankrupt (June 1925) and was subsequently purchased by Powel Crosley.
By purchasing AMRAD, Crosley was then able to legally produce Neutrodyne
The earliest of the Synchrophase receivers with no
chain-drive and no Tone Color control - from late 1924
A.H. Grebe & Company
Arguably, the Grebe Synchrophase is best performing TRF
AM Broadcast battery set
that was made in the mid-twenties. The circuit was a Neutrodyne and Grebe was sued by Hazeltine (Independent Radio
Manufacturers) because of it, though production of the MU-1 was never
stopped and continued on, ultimately reaching
over 150,000 radios. The MU-1 is very sensitive and will separate signals quite well due
to its SLF (Straight-Line-Frequency) condensers and binocular coils.
Grebe engineers considered the MU-1 Synchrophase's great performance was
due more to the design and construction of the unique precision
components used in the receiver rather than the Neutrodyne circuit.
The earliest Synchrophase receivers use
a single filament control and a volume control that selects various
resistors that are across the second audio interstage transformer primary. The small round escutcheons only had "INCREASE"
embossed on them. Shortly after "VOLUME" and "FILAMENTS" were added to
the "INCREASE" on the small round escutcheons. These early Synchrophases
only tune up to 1300kc. Several improvements were added in a mid-1925
production upgrade but the most significant improvements were the
ball-chain drive for single-dial tuning and the bandswitch that allowed increasing the
upper end of the tuning range to 1900kc. The bandswitch was actuated by the center dial at either end of its
rotation. The chain-drive could be disabled by loosening the knurled nut on top of each outer
dial. This would not affect the operation of the bandswitch but allowed
for more accurate tuning of the signals.
Other mid-1925 additions or upgrades included a "TONE COLOR" control
that was actually modified from the old "VOLUME" control. The "TONE
COLOR" was now an adjustable resistive-capacitance device installed
across the primary of the second
audio interstage transformer. The "VOLUME" control was a
modification of the old "FILAMENTS" control that changed the component
into a dual filament control
that separated the detector and AF filaments adjustment from the RF
amplifier tubes adjustment, providing better response for receiver
output. A mid-1926 upgrade
added an improved audio interstage
transformer that increased the "low frequency" response to improve the sound quality. Also
part of the 1926 upgrade was changing the audio
output tube to a UX-112A, requiring an increased B+ of
+135vdc and an increase in the -C bias to the audio output tube to
-9vdc. Additionally, the "TONE COLOR" control was changed to a
selectable capacitance that shunted the 2AF audio grid to -C. Somewhat
after the mid-1926 upgrade a cushioned detector socket was added and,
shortly after that, all of the sockets were changed to the cushioned-type. There
were no other upgrades after the mid-1926 changes and the MU-1 continued
in production until around April-May of 1927.
Throughout production there were minor
changes to the hardware and assembly, e.g., some sets are found with two
lid props and some with just one. Additionally, the dial escutcheons
were usually finished in lacquered gold but supposedly some MU-1s had gold-plated
escutcheons. Front panels will be found with either linear faux graining
or burl (mottled) faux graining. The instruction cards are found in various colors, cream
with black letters, yellow with black letters and cream with red
letters depending on the vintage of the set. To this day, Grebe's serializing of the Synchrophase remains a
serialized identification consists of four letters, e.g., "TFZH" or "BWDC",
etc. - the letters were not chronologically arranged and defy any sort
of decoding. It seems likely that the intent was to obfuscate the actual
number of MU-1 receivers being built (at least by serial number
inference) since that total quantity might
have figured in a settlement in the pending Neutrodyne suit. Included with the purchase of a new Grebe MU-1 were "Dr. Mu"
QSL cards that allowed users to send reception reports to broadcast
stations they received on their MU-1 (in the hopes of receiving a return
reply QSL card from the BC station.) "Dr. Mu" was an advertising
character that Grebe created - a fictitious ancient Chinese philosopher-scientist. "Mu" refers to µ or mu, the
gain of a vacuum tube.
There was also an MU-2
available that was a dry-cell tube version using six UV-199 tubes. Another
option was a Battery Base that the Synchrophase would set on top of. The
Battery Base was designed for the 1924 version of the Synchrophase
that used four +22.5vdc B batteries. By mid-1925, two large +45vdc B
batteries were now specified and these wouldn't fit into the Battery
Base due to their height. Owners could still operate their 1925 set on
the four +22.5vdc B batteries since the voltage requirements hadn't
changed. When the 1926 version added the UX-112 tube with +135vdc B
voltage the set now required three large +45vdc B batteries (beside two C
batteries) and there was no way to fit all of the batteries in the
Battery Base. However, by 1926, there were smaller +45vdc B batteries
available that would fit into the base but their useful life was much
shorter than the larger B batteries. Around this time, the Battery Base
was rapidly loosing any desirability as an option. Due to the later
battery requirements, most original Synchrophase and Battery Base
combinations that turn up are the earlier 1924 to mid-1925 versions. Note that the
cabinet feet must be removed from the Synchrophase cabinet in order for
it to set flush into the Battery Box recessed area.
The court case regarding the Neutrodyne
Patent infringement was heard in June, 1927. Grebe lost the case but was
able to obtain a Neutrodyne license. However by this time the MU-1 was
obsolete and Grebe production was moving to single-dial receivers, the
Synchrophase AC-6 and later the AC operated AC-7. The Synchrophase MU-1
production had run from mid-1924 up to mid-1927 and an incredible
150,000 receivers had been produced during that time.
On an additional note: Some Synchrophases will be found with a
greenish-gray color to the finish (as seen in the top photo.) This is a reaction that the original
finish has with excessive exposure to sunlight (UV.) The original finish
was medium walnut color (as seen in the lower photo.)
For the ultimate
information source on the Grebe Synchrophase MU-1, including
chronological listing of engineering-production upgrades, restoration
hints and neutralizing the MU-1, go to "A Guide to the Synchrophase
MU-1." Link below in Navigation Index.
photo above: This advertising label was installed
inside the cabinet wall on the right side. This label
advertises Grebe's Broadcast Station WAHG and also
mentions the packet of Grebe QSL cards that were
supplied with each receiver.
photo left: Grebe MU-1 CTPB with optional Battery Box. This MU-1 does not have the
chain drive and has the "VOLUME" and "FILAMENTS"
controls - no "TONE COLOR" control.
Federal Telephone & Telegraph
Type A-10 "Orthosonic"
Federal was able to become one of the Independent
Radio Manufacturers and was able to sell Neutrodynes. The A-10 is
Federal's entry-level Neutrodyne selling for
in 1925. Like all Federals, the A-10 is well-built with quality
parts, most made by Federal themselves. The Neutrodyne circuit helps
the A-10 performance but since the condensers are not
"straight-line-frequency" types, all of the stations seem crowded at
the upper end of the tuning range. Sensitivity and selectivity are
good as expected from a Neutrodyne.
This Federal A-10 has had an interesting history that
started in Bodie, California - the mining town located 9000 feet
above sea level just north of Mono Lake. The last resident of Bodie
left in the 1930s. Much of the town had burned down earlier
(although many buildings survived the fire) and the abandoned town was left
to decay in the high altitude elements. Below Bodie, at the north
end of Mono Lake, the Scarvino family had a ranch. By the 1940s,
going up to Bodie to "pick thru" the remains was popular with the
locals. Supposedly, this A-10 was picked-up by one of the Scarvinos
(along with a Cameco horn speaker) and brought back to their ranch.
Fast forward to the 1990s, when I picked up this A-10 (and the
Cameco horn) from the person
that got it from the Scarvinos. It's obvious by the A-10's condition that the radio
must had been inside one
of the many surviving houses in Bodie (from the mid-1920s up to the
1940s.) In 1964, the state of
California made Bodie a State Park and a full-time ranger is now always
on duty in town. When visiting Bodie it's hard to imagine that the
structures that have survived represent only about 10% of what Bodie was in it's heyday.
GE and Westinghouse for RCA
Why RCA offered the Radiola 20 is a mystery. RCA was
practically the only company that produced superheterodynes and here
they were offering a TRF front-end with a Regenerative Detector
followed by two stages of audio amplification. Certainly by 1925,
the Regenerative receivers had fallen out of favor with AM Broadcast
listeners who didn't like the interference caused by their
neighbor's regen-set when it was oscillating. However, some realized
that the regen-detector was about the most sensitive detector of the
day. RCA added two stages of RF amplification in front of the regen-detector
which isolated it from the antenna and eliminated that possibility
of interfering with your neighbor's radio.
Radiola 20 tuning condenser is ganged together to provide
single-dial tuning but two trimmer condensers allow for fine tuning
for best accuracy. Regeneration is labeled as "Amplification." The
two pin jacks on the right side of the panel are for an external
filament voltage meter. Using four UX-199 tubes and one UX-120 tube,
the Radiola 20 is a surprisingly good performer. The UX-120 is run
at +135vdc with a -22.5vdc bias and the RF stages are also biased
with -4.5vdc. Several different B+ voltages are required for the
circuit to perform as designed. When operated correctly and with a
good quality cone speaker, the Radiola 20 sounds good and is very
sensitive. Note that the escutcheons on this Radiola 20 are the
early versions that were given a "gold wash" - sort of a very thin
gold plating. Later versions of the Radiola 20 have bronze finish
escutcheons that are much darker.
Model 20-C "Compact"
Atwater-Kent liked the appearance of his components
and his breadboard sets reflect his opinion. However, consumers in
the mid-1920s - at least those that weren't technoids - wanted
enclosed radios that didn't show any of the tubes and wires that
radio enthusiasts enjoyed looking at. Additionally, there were the
electrophobics that were always afraid of anything running on
electricity and to them the exposed terminals of the breadboards
caused no end of concern. A-K finally enclosed the breadboard design
in a mahogany cabinet and the set was designated the Model 20.
Today's collectors have dubbed this first version the "Big Box" in
contrast to the later Model 20-C or Compact. The 20-C reduced the
size of the cabinet to the absolute minimum as there is very little
space inside the cabinet that isn't radio components. A battery
cable is brought out the rear of the cabinet to allow the set to be
connected to batteries. Terminals inside provide connections for the
horn speaker and the antenna-ground system. The 20-C was popular and
A-K sold a lot of them. High quality components and good performance
as was typical of Atwater-Kent.
American Auto & Radio Mfg. Co.
Harry Schwartzberg was president of this small company located
in Kansas City, Missouri. The American Beauty is typical of the 1925 to 1926 manufacturing
style of TRF receivers built by companies that weren't members of the Independent Radio
Manufacturers and therefore couldn't legally build neutrodynes. The circuit uses two
standard TRF amplifiers, a Detector, two stages of RC coupled Audio Amplification and one
stage of transformer coupled Audio Amplification - six tubes in all. The silk-screened
panels became popular in the same time period and in many other models these panels became
very elaborate works of art. The American Beauty artwork features a rose in each corner to
honor its namesake.
HI-MU Radio Labs, Los Angeles
Of the thousand or so
Radio Manufacturers that were around in the mid-twenties, only a small
percentage of the companies were large, well-organized and well-run
concerns. Most of the companies that show up in lists from the 1920s
were single owner-engineer organizations that might have had some
assemblers and other staff but the engineering was generally came "down
from the top" and was usually at the amateur level. Additionally, most
of these small companies operated with a very small budget and had no
capital for either R & D or any kind of expansion. It's not surprising
that with the introduction of "light socket-powered" radios in late-1927
most of these small companies vanished. They didn't have the
technological ability or the capital to make the transition from
battery-operated radios to the new "light socket-powered" radios and
therefore went out of business or sold their assets to other larger
Many small Los Angeles companies were building and selling
radios in the twenties. HI-MU Radio Labs is an unknown company that probably only built a
handful of radios. "Built by William Ferringer" is engraved on the front panel
but it is unknown what position Ferringer held at HI-MU (maybe he was the only
"employee.") This particular HI-MU is serial number 91 but that figure cannot
reliably be used as a reference for the quantity actually built. The circuit is unusual in
that only four tubes are used in such a physically large radio. An RF Amplifier, a
Regenerative Detector and two Audio Amplifiers. The AF Amps use ballast resistors to
automatically control filament voltage while the meter can be switched to monitor RF Amp
or Detector voltage. Remler tuning condensers are used along with Remler dials. Probably
dates from around 1925. HI-MU is typical of the small
individual-operated companies that produced some radios in the
mid-twenties but never progressed beyond the battery-operated radio.
Kemper Radio Laboratories
In 1927, Sennett Gilfillan and David
Sarnoff met in New York to come to an agreement as to how radio
manufacturing in the West would develop. Prior to this time, many small
companies were building radios that technically violated many of the
patents held by the "Radio Group." The arrangement that Gilfillan and
RCA worked out was that in exchange for Gilfillan shutting down its
operations in New York and Kansas City, they would be given exclusive
licenses for radio manufacture in the eleven Western states. In 1927,
this amounted to the manufacture of all TRF radios and a few other key
patents. In 1930, the licenses included the Superheterodyne. After 1930, all radio
manufacturing in the West had to go through Gilfillan with the other
builders becoming sub-contractors protected by Gilfillan's licenses.
This arrangement lasted throughout the 1930s and was only changed
beginning in 1940.
The Kemper K-5-2 Portable is a five
tube TRF receiver with the AF output using a special 3-V Van Horne tube.
10 batteries are required for power and, when not in use, the loop
antenna stows in the removable back cover, (there is also a removable
front cover that is not shown.) Kemper Radio Laboratories of Los Angeles
eventually became Kemper Radio Company. This K-5-2 dates from
about 1927. Performance is very good and sound quality is enhanced by
the use of a built-in exponential horn.
Go to our section
"Classic Pre-WWII Ham Gear"
to see a complete 1933 two-tube receiver and four-tube transmitter, both
with separate AC power supplies, all built into a
cabinet - it's impressive. Navigation link at bottom of this page.
Certainly one of the smallest
radios built in the twenties, the Beaver Laboratories' Baby Grand is shown next to a
quarter for size reference. This tiny crystal set dates from about 1922, or so. It is not
certain if the Baby Grand was originally considered a "novelty" or a
"real" crystal receiver.
Betta-tone Radio Co.
These small crystal sets, built into a file-boxes, were popular
in the mid-twenties. Construction was usually good and performance was satisfactory
considering the low price they sold for. The Betta-tone is from about 1924. Like most of
its contemporaries, the Betta-tone features a tapped coil with switched contact controls
for tuning in stations and a "cat's whisker" to find a sensitive spot on the
galena crystal for detecting the incoming signal. Earphones connect to the right binding
posts while the aerial and ground connect the left binding posts.
Philmore Mfg. Co.
Philmore Mfg. Co. probably made more crystal sets, over a longer
period of time, than any other manufacturer. Most of Philmore's line was fairly low
quality with very low selling prices. The "Blackbird" uses a coil wound on a
wooden form with a slider actuated by the tuning knob. The crystal detector has a glass
cover over the "cat's whisker." The black wrinkle finish metal case gives the
appearance of a substantial amount of circuitry but the few components used are all mounted
on the back of the unfinished metal panel. Some examples of the
"Blackbird" have a "crazed" painted front panel that usually appears to
be gold in color. Later "Blackbirds" changed the metal case to heavy
cardboard. Shown is an early Philmore from the late-twenties or
early-thirties. By the 1940s, Philmore crystal sets had molded plastic cases.
Al's Radio Shop
Crystal Set No. 2
Uncle Al's Radio Shop built the
best performing crystal sets. Using multiple coils with fairly loose coupling with
variable condensers for sharp tuning, the resulting selectivity is a "Miracle."
Uncle Al's Radio Shop is still in business in Oakland, California, (though they now sell
and service TVs.) This Miracle Crystal Set No. 2 dates from about 1925. This working
example of Uncle Al's design has received BC stations as far away as KNX in Los Angeles,
California, (approximately 500 miles distance), quite a feat for a crystal set. Antenna
was 75 feet long with earth ground, 'phones were Baldwin Type C.
It is doubtful that the CrystoFlex Company ever produced more
than just a few radios. This model has all the indicators of a set assembled from
purchased parts and then sold in the "neighborhood." Even the panel engraving
was done by hand. The circuit uses two 201-A tubes with one tube reflexed as both RF and
AF amplifier. The second tube is another AF amp and the detector is a galena crystal.
Performance is adequate but tight coupling on the RF coils results in poor selectivity and
the tuning range is narrow covering about 500kc up to 1000kc. The same circuit is shown in
a 1923 LeFax Radio Handbook which would suggest that this model is from 1923-24.
Homemade Crystal Sets
Almost everyone has at one time or another built or used a
"homemade" crystal set. They are easy to build, inexpensive and sometimes
performance can be quite good. Through the twenties, homemade crystal sets abounded with popularity
and several examples can still be found. Popular materials used for the
homemade set's coil form were
Quaker Oats, Alber's Wheat or almost any round cardboard container that was available.
Some high-class builders would opt for a pre-constructed oak box, though most builders were content with just a wooden board to mount the parts on.
The crystal set shown was built by M.H. Dodd probably in the early
1920s. Dodd's circuit is unusual in that a tuning condenser is used BUT
it's tuning the primary of the coil. The secondary is untuned.
Performance is, as expected, quite poor. I'm sure Dodd was thinking of
much earlier wireless hook-ups where tuning the antenna primary was
considered important, as in many pre-WWI types of tuners. It became more
common to tune the secondary with an air variable capacitor after WWI..
We have several Dodd pieces including his complete 1912
Wireless Station - for details see M.H. Dodd's 1912 Wireless Station in
the navigation Index below.
Early AC Radios (1927-1929)
Model 37 - "Modernistic Style"
The Model 37 was Atwater-Kent's first, self-contained, AC
operated radio (the Model 36 had a separate, AC power pack.) Rugged construction and
the TRF circuitry resulted in a reliable, good performing radio. Although
nearly all of
the Model 37 production was finished in a brown wrinkle finish called "Crystaline
Enamel", sometime in the production year of 1928, a small number of
Model 37 radios were finished in an
"art deco" style. These Model 37s were dubbed "Modernistic Style" and
featured a matching Type-E speaker. The silver and black decor was
achieved by using stencils and a light spray painting technique -
something like "air brushing." The finish was very thin and thus
was subject to much wear. It's very common to find "Modernistic Style"
cabinets with a lot of chips and scratches. Originally, the paint on the
"Modernistic Style" was not a glossy finish but was more of a "matte
finish" or "semi-gloss." There are two variations of the Type-E speaker.
When the "Modernistic Style" matching speaker was fitted with the "thin
wood" type of cone, the cone was painted flat black. When the "Modernistic
Style" matching speaker was fitted with the thick embossed paper cone,
the cone was painted silver. The Type-E speaker shown above has the
paper cone and is all original with its proper silver paint. Estimated
production is around 10,000 radios, which for Atwater-Kent was a "small
run." Today, the "Modernistic Style" is rarely seen. Fortunately, most
examples that turn up seem to have the matching Type-E speaker still
with the radio - probably because it's pretty obvious that the two
pieces went together. This
particular "Modernistic Style" was originally purchased in San
Francisco and for years made its home in San Francisco's
Recently (2012,) the television show
"American Restorers" featured a "Modernistic Style" radio as one of
their restoration projects. Besides several factual errors being presented as expert knowledge, the restoration itself was
inaccurate and incomplete. I suppose stating a few times that the radio
was a 1926 model was just an oversight by the writers but even the most
novice of radio collectors would know that the major introduction of
AC-operated radios was announced in late-1927 and that most production examples are
actually from 1928. The melting out of the black wax in the power supply
box was accomplished with a propane torch - very funny. Most restorers
would have used a small oven (like a "used" toaster oven) to slowly
melt-out the wax (or maybe even used the old freezer trick.) Plastic
wire used in the restoration was inexcusable since there are many
sources for the correct original type wire. While the new paint job
was stunning, it was finished off with several "clear coats" to make the
end-result super glossy - beautiful, but not very accurate. The panning close-up shots
of the cabinet revealed a missing Dial Index piece. These are easy to
find (or replicate) - why was it left off? The vacant holes above the tuning dial
should have been a clue that something was mounted there. Perhaps the
most incredible part was the cost of the restoration - $1100 - Wow! Like
most of what you see on television, "American Restorers" is an
entertainment program and what is presented there should not be taken as
expert advise or even correct information - especially when it comes to
radios and radio restoration.
The Model 40 was one of the most popular of the metal boxed,
AC-operated radios produced A-K. Probably, the reason that so many
have survived is that the radio was built like a little "tank."
There might be problems that develop in the power supply which is
filled with hard wax. This makes repair of the power supply somewhat
difficult. However, many Model 40 still operate fine on all-original
parts. A-K made all of their own components and most of them were
high-quality parts. The 1928 A-K Model 40's circuit is TRF and uses seven tubes.
The Model 36 was the first AC-operated radio from A-K in 1927 and the Model
37 was the first AC-operated metal box radio with built-in power
supply (and the Model 35, a six-tube
battery set from 1926, was the
first A-K metal box radio.) Arthur Atwater-Kent felt that the mahogany
wooden cabinets he had been making cost too much to manufacture. He knew that a
stamped steel cabinet would be cheap to make. It could be painted
which was also cheap and easy to do. He just had to convince
would-be radio purchasers that these painted steel boxes were stylish and
would fit in with the late-twenties decor. With a lot of advertising, A-K was able to change the tastes
of radio buyers and the metal box radios became quite popular for a
short time, about 1928 up to 1930. A-K even sold a console radio in
a metal cabinet. Today's tastes are very different and many
collectors find all of the metal box radios ugly, regardless of who
the manufacturer was.
The A-K Model 40 shown belonged to M. H. Dodd and was acquired along
with Dodd's 1912 Wireless Station in 1999. This Model 40 has the
earlier style tuning dial. Later versions have larger numbers and a
different style grip. While the Model 37 top tag depicted the
Mayflower (or, at least, a sailing ship,) the Model 40's tag just
has "ATWATER-KENT" embossed on it.
Screen-Grid Model 55
One of the last of the stamped metal box TRF radios from Atwater-Kent, the Screen-Grid Model 55
uses type 24-A tubes. These are tetrodes which have more gain than the
type 26 triode tubes used in earlier models. The Model 55 also uses
an electro-dynamic speaker, housed in a round metal cabinet that is
mounted to a small pedestal. The design of these speakers are very close to the speakers used in all later
radios consisting of a field coil magnet and a low-Z voice coil with
paper cone. Some of the construction is slightly different in that a separate
suspension is used around the rim but basically the A-K speaker is
modern in design. Sound quality (for a 1929 table radio) is very good.
The Model 55 was a departure for A-K in the paint finish. Unlike the
earlier metal boxes, the Model 55 is painted with high-gloss lacquer.
This particular one is in black and green, however sometimes black
and red was used. Since the finish was smooth and glossy, it's very
unusual to find any Model 55 that's in good condition, cosmetically
anyway. Most examples are severely chipped because the smooth
lacquer didn't have the durability of the heavier wrinkle finishes.
The Model 55 shown is the best condition one I've encountered. There
are a few chips where the speaker sat on top of the set but otherwise it's
in excellent condition. Nice cosmetics really doesn't help since
most collectors still find these metal box radios hideous looking.
RCA's "tour de force" superheterodyne, the Radiola
60, was certainly the best performing superhet available in 1928. AC
operation, 9 tubes, powerful sounding audio from a single-ended 71-A, cathode
type 27 tubes used in the rest of the radio with the exception of
the type 80 used for the rectifier. The Radiola 60 was well-built
and today many still function quite well on all original parts. The
weakest point of the radio is the multi-tap wire-wound resistor used
to reduce voltages for various functions. Since this puts the B+ in
a series string, if any section of the resistor opens, then the
radio will not function. It's easy to repair by installing a
correct value WW resistor across the open section. With an outdoor
antenna, the Radiola 60 will pick-up just about any signal on the AM
BC band. Unfortunately, RCA didn't include a calibrated dial, the
Radiola 60 uses a 0-100 scale on the tuning.
There were a few different speakers available for
the Radiola 60. The Radiola 100A was a metal "mantle clock shaped"
that sounded quite nice. The speaker shown in the photo left is the Radiola 103 "Tapestry" Speaker. The frame of the speaker is made out
of "repwood" or sirocco, a pressed wood that could be molded into
any shape. This was then stained. The speaker mounts to the back of
the frame and then a cardboard cone was mounted behind the speaker.
The cardboard cone was covered with very fine brown cloth. For not
having a true cabinet, the Radiola 103 sounds surprisingly good.
The first vintage radio that I bought for myself was a Radiola
60. I was fourteen and paid seven dollars for it (in 1964.) It was a consolette Radiola
60 sold by Sherman-Clay in 1932. Sherman-Clay had bought "left
over" production Radiola 60s (very cheap in 1932.) They then had a
local California cabinet shop build the console base and install a Jensen Concert Dynamic Speaker.
These radios were then sold as "new" models in 1932. The Jensen
speaker does make the Radiola 60 sound like a 1930s console.
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