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When the generator
is set up as a heterodyne-
frequency meter, the frequency of an external signal
may be determined quickly by feeding the signal into
the WR-99A and zero beating it with the
vfo
signal.
The frequency is then read directly from the dial scale.
A slide-switch type of attenuator
is used with the
WR-99A to provide attenuation
in continuous
steps
over a range of 60 db on all frequencies.
A special
coaxial cable is provided with the unit for coupling
into the test circuit.
Circuit design and layout provide a flexible system
of modulating
the rf output. For example, when the
WR-99A is used in conj unction with a sweep generator
and an oscilloscope
to reproduce
a sweep-response
curve, the 4.5-Mc crystal oscillator will modulate the
output from the WR-99A to produce
dual markers
spaced exactly 4.5 Mc apart on the curve. With output
set to the frequency of the picture carrier, for example,
the second marker
will appear
at the point on the
curve corresponding
to the sound-carrier
frequency.
The vfo signal also may be modulated internally with
both 4.5 Me and 600 cps, a useful feature for adjust-
ment and alignment
of sound-if
amplifiers
and de-
tectors. The 600-cps modulation is also used to produce
a horizontal-bar
pattern when the output signal is set
to the frequency of the picture carrier or picture inter-
mediate frequency. The 4.5-Mc output signal may be
modulated
with 600 cps for visual alignment of the
detector.
A special socket located at the rear of the WR-99A
permits the connection of an external crystal or L-C
circuit into one of the internal calibrating
oscillators.
When an external frequency-determining
unit is used
it is possible to produce calibrating
beats at intervals
other than 1 or 10 Mc.
The RCA WR-99A is designed
for both general
service and production
use. The unit measures 10" H
x 13%"
W x 7" D and weighs 17 pounds.
The
WR-99A is housed in a blue-gray
hammeroid
case
with a satin-aluminum
panel.
Description
The RCA WR-99A Crystal-Calibrated
Marker Gen-
erator is designed for use in alignment and trouble-
shooting of black-and-white and color-TV receivers, fm
receivers, and other equipment
operating
in the fre-
quency range from 19 to 260 Mc. The WR-99A pro-
vides an rf-output signal from 19 to 260 Mc in eight
bands on fundamental
frequencies,
A wide choice of
modulation
facilities is provided,
including
4.5 Mc,
which produces
dual markers
on a sweep-response
curve to mark the picture- and sound-carrier
points
on the
curve,
An extremely
versatile
instrument,
the WR-99A
combines the functions of a marker generator, a hori-
zontal bar pattern
generator,
and a heterodyne-fre-
quency meter. The frequency of the internal variable-
frequency
oscillator,
as well as the frequency
of an
external signal, may be checked with high accuracy
against internally generated calibrating
beats at 1- or
10-Mc intervals
throughout
the tuning
range. The
WR-99A includes a harmonic crystal oscillator and a
I-Mc oscillator which is coupled to the 10-Mc crystal
oscillator for accuracy. Both these oscillators may be
switched in or out from the front panel and provide
audio
calibrating
beats
from
the speaker
in the
WR-99A. Calibration
of the WR-99A may be checked
at 242 intervals throughout
the tuning
range,
Calibra-
tion of the instrument
is straightforward;
no charts
are needed.
The tuning dial is specially marked with all vhf
sound- and picture-carrier
frequencies
as well as im-
portant intermediate
frequencies in the 20· to 30-Mc
and 40- to 50-:'\1c regions.
In addition,
important
color-TV frequencies are also marked on the dial scales.
In TV servicing, the WR·99A may be used in check.
ing alignment and bandpass characteristics
of rf and
if circuits and the scanning linearity
of vertical-de-
flection circuits. The instrument
may also be used to
signal trace and trouble-shoot television receivers, and
is useful in locating defective sections and stages.
• 3 •
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