TELEVISION NUMBER - AmericanRadioHistory.Com

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460
Radio News for November, 1928
LAB(RATORCE
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manufacturers arc invited to send to RADIO NEWS LABORATORIES
RADIO samples of their products for test. It does not matter whether or not
they advertise in RADIO NEWS, the RADIO NEWS LABORATORIES being an independent
organisation, with the improvement of radio apparatus as its aim.
/f, after being tested, the instruments submitted prove to be built according
ro modern radio engineering practice, they will each be awarded a certificate
cf merit; and that apparatus which embodies novel, as well as meritorious
features in design and operation, will be described in this department, or in
the "What's New in Radio" department, as its news value and general interest
for our readers shall deserve. If the apparatus does not pass the Laboratory
tests, it will he returned to the manufacturer with suggestions for improve.
meats. No "write-ups" sent by manufacturers are published in these pages,
and only apparatus which has been-tested in the Laboratories and found of
good mechanical and electrical construction is given a certificate. As the sere -
vice of the RADIO NEWS LABORATORIES is free to all manufacturers, whether
they are advertisers or not, it is necessary that all goods to be tested be forwarded
prepaid, otherwise they cannot be accepted. Apparatus ready for, or
already on, the market will be tested for manufacturers free of charge. Apparatus
in process of development will be tested at a charge of $2.00 per hour
required to do the work. Address all communications and all parcels to RADIO
NEWS LABORATORIES, 230 Fifth Avenue. New York City. Readers will be informed
on request if any article has been issued a Certificate of Merit.
AUDIO -FREQUENCY
TRANSFORMER
The "Type AX" audio -frequency
transformer shown, submitted by the
Sangamo Electric Company, Springfield,
III., is of excellent mechanical
and electrical design. The amplification
of the transformer maintained
a value almost constant from 32 to
5,000 cycles, when used with the
201A -type tube. The primary in-
ductance, with a
plate current of
3 milliamperes, was found to be
approximately 80 henries. The
transformer has a ratio of three to
rie; and excellent quality with great
volume was obtained when it was
used in the conventional audio am-
plifier employing the 201A and 171
tubes. The transformer is identified
by a yellow spot. The core and
winding are completely shielded by
an iron housing of olive -green finish.
The dimensions of the base are 2%
x 2h inches, while the height is 3
inches.
AWARDED TI1E R. \DIO NEWS
LABORATORIES CERTIFICATE
OF MERIT NO. 2421.
AUDIO -FREQUENCY CHOKE
The "Type E" audio- frequency
choke or "impedance" submitted by
the same manufacturer, is of the
same size and shape as their "Type
AX" A.F. transformer illustrated
above. It is used as an output impedance
for the 171 -type power tube.
in which case the entire inductance
is employed.
It may he used also
as an output impedance for the 112 -
or 210 -type power tubes, by using
the portion of the winding between
"T" and "B } "' It is designed to
match the impedance of the modern
power tubes and, for this reason,
allows the lower frequencies to be
better reproduced. When it is emrloyed
in the output circuit, a blocking
condenser external to the choke
must also be used; this should have
f rom 2 to 4 tuf. capacity, and be
of voltage rating suitable to withstand
safely the maximum voltage
of the power stage. The inductance
was found to be within 10% of
the rated value of 30 henries, when
measured at 60 cycles; the ohmic
resistance is approximately 570. The
metal case is finished in dark red
and the device is identified by a
"mandarin red "' spot.
AWARDED THE RADIO NEWS
LABORATORIES CERTIFICATE
OF MERIT NO. 2422.
AC- OPERATED RECEIVER
The "Packard" 8 -tube radio receiver
shown, submitted by the Packard
Radio Co., 2161 No. California
Ave., Chicago, Ill., is of the all -
electric type, using five 226 A.C.
tubes, one 227 A.C. (heatéd- cathode)
detector tube, and two 171 power
tubes; it operates directly from the
110 -volt, 60- cycle, house- lighting circuit.
The low -voltage A.C. current
for the filaments of the tubes is
supplied by separate windings of the
power transformer, and the "B"
voltages are provided by a full -wave
rectifier of the 280 type in connection
with an efficient filter system,
the chokes of which are contained
in the same metal housing with the
power transformer. Three stages of
tuned radio frequency of modern design,
using 226 -type tubes, give ample
selectivity and sensitivity. The
tuning inductors are of the compact,
small -field type, enclosed in indi-
vidual shield cans. The radio -frequency
stages are followed by a
conventional 227 -type detector, which
feeds into two stages of transformer -
coupled (1:1 ratio) audio frequency,
followed by a stage of push -pull
power amplification of the 171 type.
The speaker windings are protected
by a balanced output choke. The
tuning of the R.F. and detector circuits
is accomplished by one control,
which is .geared to the common shaft
of the condenser rotors; the scale is
of the drum type. A fine adjustment
of tuning for DX work is accomplished
by means of the levers protruding
through the panel on each
side of the tuning control. A power
rheostat with a panel voltmeter is
provided. to maintain the filaments
of the tubes at the proper temperature.
The control at the right of
the set is provided for controlling
oscillations and volume, and there is
a sub -panel adjustment to balance
out the hum in the R.F. and 1:1-
ratio audio stages. The filament
circuits of the detector and the
power tubes are automatically balanced
by center- tapped windings. The
receiver is of attractive appearance,
and its operation, with regard to
sensitivity, selectivity, quality, volume,
and elimination of the A.C.
bum, is satisfactory.
AWARDED THE RADIO NEWS
LABORATORIES CERTIFICATE
OF MERIT NO. 2423.
PHONOGRAPH PICK -UP
The "Via-Rad" phonograph pick-up
device shown, submitted by the
Brooklyn Metal Stamping Corp.,
718-728 Atlantic Ave., Brooklyn,
N. Y., is of the magnetic type and
makes it possible to reproduce speech
and music from ordinary phonograph
records, when it is used in connection
with an audio -frequency amplifier.
It is of the balanced- armature
type; the airgap between the pole
pieces is adjusted in the factory before
sealing. The magnets are of
the bar type and situated on each
side of the adjustable pole pieces
in such positions that their fields
assist. Their magnetic strength is
great, resulting in a very sensitive
and loud reproducer. The frame or
base which supports the coil, armature,
and pole pieces, the dimensions
of which are 11/4 x 2 inches, is cast
of aluminum alloy. The end of the
balanced armature protrudes through
the metal housing and carries at its
end the socket and fastening screw
for the phonograph needle. The device
is fitted with a flange, designed
to fasten over the tone arm
of the phonograph after the usual
reproducer has been removed. The
over -all dimensions are 2j inches
long, 2 inches wide, and 1g inches
high; and the weight 8 ounces. The
housing is of a gold - finish.
AWARDED THE RADIO NEWS
LABORATORIES CERTIFICATE
OF MERIT NO. 2424.
PICK -UP VOLUME CONTROL
The "Via-Trot" phonograph pickup
device volume control shown, submitted
by the same manufacturer,
is of the graphite -and -powdered-mica
compression type; it has a resistance
range from 0 to 500,000 ohms and
is to be shunted across the terminals
of the phonograph pick -up device.
This resistor is provided with cord -
tip jacks, two on each side of the
housing; the tips of the pick -up are
plugged into one pair of jacks, while
those of the receiving -set adaptor
are plugged into the other pair. The
case or housing is of brown molded
bakelite of pleasing appearance, the
top is of gold- finished die -stamped
metal, and the adjusting knob is
molded of the same colored bakelite.
The diameter of the base is 21/4
inches and the height over all 2V
inches. The device has proved satisfactory
in giving smooth control of
volume when used with the pick -up
manufactured by the same concern.
AWARDED THE RADIO NEWS
LABORATORIES CERTIFICATE
OF MERIT NO. 2425.
PHONOGRAPH PICK -UP
ADAPTOR
The "Via-Tector" home broadcaster
and pick-up adaptor device
shown, submitted by the same manufacturer,
is of the UX type and
designed to be plugged into the detector
socket of the radio receiver.
If it is so desired, the detector tube
may be plugged into the adaptor;
thus utilizing this tube as an additional
stage of audio frequency.
Otherwise, the tube may be replaced
by a jumper, which is plugged into
the socket, thus allowing only the
audio -frequency stages of the set to
function. The device is of black
molded bakelite and approximately
the size of the standard UX tube
base; it is provided with a four -
foot extension cord, the tips of
which may be plugged into the volume
control described above.
AWARDED THE RADIO NEWS
LABORATORIES CERTIFICATE
OF MERIT NO. 2426.
A.C.-OPERATED RECEIVER
The "Model 801A" radio receiver
shown, submitted by the Stewart -
Warner Speedometer Corp., 1834
Diversey Parkway, Chicago, Ill., is
of the all- electric type and operates
directly from the 110 -volt, 60 -cycle
house current. The receiver uses
four 226- types, one 227 -type, and
one power tube, in three stages of
tuned radio frequency, detector and
two stages of audio frequency; the