The Tektronix 180A was introduced in 1958 and is an all tube time mark generator with an oven-controlled crystal oscillator (OCXO). Time mark generators put out pulses at user-selectable intervals. They are primarily used for calibrating the time-base of oscilloscopes. The 180A divides down the clock signal using synchronized monostable multivibrators. This scheme does not require precision in the time constant of the monostable multivibrators. The only precision component in the 180A is the OCXO (part number 158-007). The manual suggests an interesting procedure for calibrating the OCXO, by attaching a small antenna to deliberately interfere with the national time standard broadcast, and observing the interference with a communication receiver.
The Tektronix 180 has toggle switches. The 180A has pushbutton switches.
- Tektronix 180A Manual (PDF)
- Tektronix 180 Field Recalibration Procedure (PDF)
- Tektronix 180A Factory Calibration Procedure (PDF)
Oscillator circuit in 180A using 158-007