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RCA Cryaral-Cahbrated
Marker Generator
WR-99A
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Figure 2_ Dial scale. for WR-99A. N,ote the most-u.ed TV frequenci •• are spotted individually.
with the dial-scale calibration
mark. NOTE: Leave the
RF TUNING control set to the zero-beat setting while
making this adjustment. The dial pointer has approxi-
mately 1 inch of play, permitting correct calibration at
the nearest· calibrating
point.
After setting the dial pointer at the 10 MC check
point which is closest to the desired frequency,
set
the CAL/MOD
control to the "IMC CAL" position.
Adjust the RF TUNING control to pick up the 1 MC
beat at the point nearest the desired frequency. If the
pointer does not coincide exactly with the 1 MC cali-
bration mark on the tuning dial, slide the pointer to
the left or right as required to line the pointer up with
the dial scale calibration mark. Leave the RF TUNING
control set for zero beat while making this adjust-
ment. The calibration
is now accurate
at this 1 MC
point and for some distance on either side.
The WR·99A should always be calibrated
at
the beat point which is nearest to the frequency
to
he
used.
As an example, if it is desired to set the generator
accurately to 45.75 MC, the procedure is 'as follows:
1. With the CAL/MOD
control in the 10 MC CAL
position, pick up the 50 MC beat on the 39 to 50 MC
dial scale. Slide the pointer, if necessary, to coincide
with the 50 MC dial scale calibration
mark.
2. With the CAL/MOD
control in the 1 MC CAL
position, pick up the beat at 45 MC. Slide the pointer,
if necessary,
to coincide with the 45 MC dial scale
calibration
mark.
3. The calibration is now accurate at 45 MC. Adjust
the RF TUNING control so that the pointer lines up
with the 45.75 MC mark on the dial.
Calibration from an External Source
The two-pin socket in the rear of the WR-99A case
(see Figure 4) connects to internal circuitry and per-
mits use of an external crystal or L-C circuit in cali-
brating the WR·99A at other than 1- or 10·Mc inter-
vals. In addition, when the vfo in the WR-99A is made
inoperative
the modulating signal of the external unit
is available separately at the OUTPUT connector. For
example,
any fundamental-cut
crystal
in the range
from 1 to 30 Me or a Colpitts-type L-C circuit designed
to operate from 100 Kc to 10 Mc, in which the point
between the two capacitors
is grounded, may be syn-
chronized with the internal oscillator circuit. The ex-
ternal unit will produce audio beat signals up to about
the tenth harmonic
at frequencies which are multiples
of the natural resonant frequency of the crystal or L-C
circuit. In addition to these two special applications,
an appropriate
external unit may be synchronized with
the internal
I-Mc crystal oscillator
to give accurate
·7.
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