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28
simply,
a transistor
consists
of a ''sandwich"
of various
alloys
of germanium.
Three
layers
of the
alloys form this sandwich.
A connecting
lead is attached to each of the layers
and brought out for ex-
ternal connections,
OPERATION
Operation of the UXR-1
Transistor
Receiver
is simple
and conventional,
Turn
on the receiver,
select
the desired
station and adjust the volume.
Because
the
antenna
coil
tends
to give directional
results,
the receiver
should be rotated to provide
maximum
volume
of the
desired
station.
In some
instances
this may
prove
helpful in reducing un-
wanted
interference by careful positioning of the receiver.
No pilot light is provided
to indicate when
the
receiver
is turned
on
because
the
light would
consume
about
10 times
the power
required by the
receiver
and severely
reduce
battery life.
Make
it a habit to turn off the receiver
after use to obtain
maximum
battery economy.
Reception
in cars,
trains
and aeroplanes
is possible in most
locations,
It may
be necessary
to place
the receiver near
a window of the vehicle
for best reception
because
the metal
body will act as a shield
against
the reception
of radio
signal.
In general,
much
better
results will be obtained
by using a car
aerial and a socket
is provided
for this purpose.
The batteries
will normally
provide
300 hours
or more
reception before
requiring
replacement.
Signs
of weak
batteries
are
low
volume,
excessive
distortion and failure to operate
at some
section of the
dial,
ALWAYS
REMOVE
EXHAUSTED
BATTERIES
IMMEDIATELY,
OLD
BATTERIES
MAY
SWELL
AND
MAKE
REMOVAL
DIFFICULT,
OR
THEY
MAY
LEAK
CHEMICAL
COMPOUNDS
THAT
WOULD
COR-
RODE
THE
CHASSIS.
DO NOT
STORE
FOR
EXTENDED
PERIODS
WITHOUT
REMOVING
THE
BAT-
TERIES.
BE SURE
TO OBSERVE
BATTERY
POLARITY
WHEN
REPLACING
THE
BATTERIES.
THE
BATTERIES
MUST
BE
INSTALLED
EXACTLY
AS SHOWN
IN THE
DIAGRAM.
THE
RECEIVER
WILL
NOT
OPERATE
AND
POSSIBLE
DAMAGE
MAY
RESULT
THROUGH
IMPROPER
BATTERY
POLARITY.
CIRCUIT
DESCRIPTION
The
model
UXR-1
is a six transistor
portable
receiver
very
similar
in most
respects
to a valve type
receiver,
Thoseof you whoare
familiar with the circuitry used in superhetrodyne
receivers
will rec-
ognise
the
similarities
and
quickly
understand
the
difference
in the
circuit
required
for transistor
operation.
Those
of you
who are not familiar with component
and circuit terminology,
or the
nature
and function, should refer tothe glossary at the end of this section to gain a better understanding
of the
circuit.
Refer to the circuit diagram
on page 2 as you read,
Signals
picked
up by the ferrite
aerial
coil are tuned or selected by the large section of the variable
condenser and fed to the base of the TRI
transistor
by the small low impedance
coupling coil wound
on
the
rod.
The
small
section
of the
variable
condenser
tunes the oscillator
coil connected
to the TR1
transistor
and the base voltage is provided
by the 10K and 56K resistors.
The
3.9K
resistor
provides
emitter
bias
voltage,
The
470
kc/s.
output
from
the
TR1
converter
or frequency
changer
is trans-
former
coupled
to the
base
of the first I.F.
amplifier
TR2,
The amplified
output from
this
stage is
transformer
coupled
to the
second
I, F. amplifier
using
a similar
transistor,
TR3.
Both
amplifier
stages
use
voltage
divider
networks
to supply
bias
voltage to the transistor,
Base
and Emitter bias
resistors
are
also
employed.
Output
from
the
second
I, F.
amplifier
is transformer
coupled to
the
diode detector which is followed by a volume
control,
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