Filter
Top Products
Independent
Power
Supply
For
Local
Oscillator
One consequence
of the
relatively high impedance
of
power supplies
is
that leakage from
the +B
line
of the
power supply unit
can
feed back
to the
local oscillator
to
modulate
the
local oscillator frequency. This causes tuning
inaccuracies
by
deflecting
the
tuned frequency above
and
below
its
optimum
level.
Kenwood engineers solved this
problem
by
eliminating
the
source itself
—
the +
B
line
to
the oscillator, giving the local oscillator its own independent
power supply. With
two
power supplies, noise
due
to
leak-
age
is
virtually non-existent, even
at
100%
modulation.
In
the KT-1000, this
is
perfectly utilized.
High
Quality
AM Section
In
the
past,
AM
sections
of
FM/AM stereo tuners have
tended
to be
neglected because
of the
generally inferior
quality
of AM
broadcasts.
Now,
Kenwood tuners
are
fully
able
to
reproduce
the
upgraded
AM
broadcast quality, with
AM sections that are as carefully designed as FM sections.
In
the
KT-1000
an
IF
band selector
is
provided
for
the
AM
section.
Sample-And-Hold
MPX Circuit
As
with the Pulse Count Detector, Kenwood engineers have
taken advantage
of
the exceptional accuracy
of
digital pro-
cessing with
the
introduction
of
the Sample-and-Hold
multi-
plex decoder. This circuit cleanly extracts the left and right
channel signals from
the
composite
FM
signal carried
by
the
38
kHz subcarrier frequency. The wave peaks are
con-
verted into digital equivalents
in the
form
of
pulses. Since
only the basic shape
of
the waves are converted into digital
equivalents, transient deflections
in the
shape
of
waves
caused
by
noise
or
distortion
are
ignored. This greatly
reduces
the
need
for
filtering,
which vastly improves chan-
nel separation, because filtering
can
obscure important
information
in
the composite
signal,
interfering with the
abili-
ty
to
isolate left and right channel signals.
The
peak pulses
are sampled then held in
a
capacitor until the next peak
ar-
rives;
thus,
the average peak value
can be
instantly adjusted
for precise representation
of
the original 38 kHz subcarrier.
The KT-1000 employs this superior type
of
MPX
decoder.
Quartz
Synthesizer
Preset
Tuning
Kenwood's quartz-PLL tuning circuit uses
the
ultra-stable
oscillating frequency
of a
quartz crystal
to
keep
the
fre-
quency generated by the local oscillator
locked
to the exact
tuning frequency.
The
quartz-PLL circuit
can
be
preset
to
automatically tune
to any one of any
combination
of as
many
as
eight different
FM or
AM
stations.
To
preset,
the
desired station
is
manually tuned
in, and
then
the
preset
button
is
pressed, after which
any one of
eight station
buttons
may be
pressed. Whenever that station
is
desired,
pressing
the
station button previously selected will
automatically tune the
station.
This system is fully utilized
in
the KT-800.