Note
The National Company XCU27 (often written as the XCU-27) is a crystal calibrator designed specifically for use with high-end National amateur radio receivers. Compatible with NC-140, NC-190, and NCX-3, but can be adapted to just about any receiver.
Crystal: 100 kHz.
Filament Voltage: 6.3V AC or DC.
High Voltage (B+): 150V to 300V DC.
Tube: 6AK6 or 6BJ6
Output: 100 kHz or 1.0 MHz
