The XCU-300 Crystal Calibrator provides a means of checking the accuracy of the frequency calibration of the NC-300 and NC-303 receivers. The front-panel mounted OFF-CAL-WWV switch connects B-plus to the calibrator for instantaneous service. To check calibration accuracy tune in the desired marker signal with the MODE switch set at CW and the CWO knob set at 12 o'clock. Zero beat the receiver with the harmonic marker. If the slide-rule dial does not read accurately correction should be made by adjusting the front-panel mounted CAL-SET control. Only a slight adjustment of the CAL-SET control should be necessary.

The XCU-300 Crystal Calibrator is installed in your NC-300 or NC-303 receiver by plugging the unit into the Crystal Calibrator Socket, X1, on top of the chassis.

Scematic for the XCU-300 calibrator

C1 Ceramic, variable 6-20 mmf
C2 Ceramic, 10 mmf, 500 vdcw
C3 Ceramic, 3 mmf, 500 vdcw
C4 Ceramic, 220 mmf, 500 vdcw
L1 5 mh, type R-100
P1 Octal
R1 Fixed, 4.7 megaohms, 1/2 watt
R2 Fixed, 470,000 ohms, 1 watt
Y1 Quartz crystal, 100 kc

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