Crystal Calibrator for Wireless Set No. 19

The NT-11 Crystal Calibrator is a test oscillator used to tune accurately the A-set of Wireless Set No. 19. It may also be used with other sets. The unit was developed and produced in Canada and principally used in the Canadian Army. Officially it was not introduced for use in the British Army, who relied on the Wavemeter Class D No. 1. Electrically the Crystal Calibrator NT-11 is similar as used in the receiver unit of Canadian Wireless Sets No. 9 and No. 52. The installation kit included a Slow Motion drive which was intended to replace to original knob on a Wireless Set No. 19 Mk.II.

• Provides frequency markers at every 1MHz, 100kHz or 10kHz.
• To distinguish marker from other signals, a modulator is included in the NT-11.
• The Crystal Calibrator is normally mounted on the No. 19 Set Supply Unit.
• A special connector, replacing the original one, has an extra power lead for connecting the NT-11.
• Three 12SC7 valves are employed.

Inside view of Crystal Calibrator. Note that two spare valves are carried inside the unit. The crystal holder (vertical brown block in centre), is mounted just below the coil unit.

Fitting the Crystal Calibrator NT-11 on a Canadian Wireless Set No. 19 Mk.III. Note special 12-pt connector with supply lead for calibrator.