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Calibration and Operation
General
Before the WR·99A is put into use, it is important
that the functions
of controls and uses of the con-
nectors be understood.
The purposes of the controls
and connectors
are described
under
"Functions
of
Controls".
This section explains how to calibrate the WR·99A
and how to set up the instrument
to provide an
un-
modulated marker signal of a desired frequency, or .a
marker signal which is modulated
with one or more
different modulating
signals. Some important
sugges-
tions are also given for connecting the WR·99A to the
equipment under test and to auxiliary test equipment.
Because the Applications
section does not include
instructions
for setting up and adjusting the WR·99A,
the user should first make sure he understands
the
operation of the instrument
before using it in align.
ment applications.
WR·99A Dial Scales
The 20 to 260·Mc tuning range of the WR·99A is
divided
into
eight
convenient
tuning
ranges
(see
Figure
2). The most-used frequencies
in the inter-
mediate-frequency
and channel- frequency
ranges are
spotted individually
on the scales. For example, 21.25
and 25.75 Mc are spotted on the first range and -the
intercarrier
intermediate
frequencies
of 41.25
and
45.75 are spotted on the third range. In the TV -carrier
ranges, the picture. and sound-carrier
frequencies are
spotted individually
to facilitate alignment.
All these
frequency settings should be used only after the WR·
99A has been calibrated
against the nearest crystal
check point, as described elsewhere in this section.
I
(
Figure 1. IF· output cobl. lupplled with WI-99A.
Calibration
I·Me and IO-Mc Calibration
Calibration
of the WR·99A is necessary before the
instrument
can be used to provide accurate
marker
signals. Calibration
is accomplished by beating the in-
ternal variable- frequency oscillator signal with either
1· or IO·Mc internal oscillator signals. These oscilla-
tors provide harmonic
calibrating
signals throughout
the tuning range of the WR·99A. Thus, it is possible to
accurately
calibrate
the WR·99A at I·Mc or lO·Mc
intervals from 20 to 260 Mc.
As the tuning dial is turned, beat notes other than
those at 1· or 10·Mc intervals will be heard. It will be
necessary to exercise care to avoid confusing
these
extra beat notes with the normal
calibrating
beats.
These extra beats are weaker than the normal cali-
brating beat notes, and are usually more prevalent on
the lower ranges. The extra beat notes are caused by
harmonics
of the calibrating
oscillator
beating with
harmonics from the variable-frequency
oscillator. Cali-
bration procedure is as follows.
Connect the power cord to an ac outlet supplying
105·125 volts, 50·60 cps, and tum the AF GAIN con-
trol clockwise from the "POWER OFF" position. Allow
15 minutes for the instrument
to reach a stable oper·
ating temperature.
1. Connect
the
output
cable
to
the
OUTPUT
connector.
2. Set the RF RANGE control to the desired fre-
quency range, as indicated on the dial scales.
3. Set the CAL/MOD control to the "10 MC CAL"
position.
4. Set the RF control to "ON".
5. Adjust the RF TUNING control to position the
dial pointer at the desired IO·Mc calibration
point on
the tuning dial. A strong beat note should be heard
from the speaker. Carefully adjust the RF TUNING
to obtain zero beat.
6. Observe the position of the dial pointer. If the
pointer does not coincide exactly with the IO·Mc cali-
bration mark on the tuning dial, slide the pointer, by
means of the small knob at the bottom of the pointer,
to the left or right, as required, to line the pointer up
• 6 •
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