In the world of electronics, reliable frequency generation is paramount. The component at the heart of many precision timing applications is the quartz crystal unit. Today, we examine the specifics of a particular military-grade component: the **5955-00-068-1300** Quartz Crystal Unit, also known by its specification number **CR-53A/U68.778000MHZ**.

Technical Profile: A High-Performance Resonator

This specific crystal unit is designated by the Item Name Code 00196 (CRYSTAL UNIT, QUARTZ) and falls under Federal Supply Group (FSG) 59. Its defining feature is its highly stable oscillation, crucial for maintaining accurate time bases or carrier frequencies in complex systems.

Key Performance Characteristics:

• Specified Frequency: A precise 68.778 Megahertz (MHZ).
• Mode of Oscillation: It operates on the FIFTH OVERTONE, allowing for stable operation at this relatively high fundamental frequency equivalent.
• Circuit Resonance: Designed for SERIES RESONANCE operation.
• Tolerance: The frequency stability is tightly controlled with a tolerance specification of ±0.005% (M0.005/P0.005) across its operating temperature range.
• Temperature Range: Robust operation across extreme environmental conditions, specified from -55.0 to +105.0 degrees Celsius.
• Equivalent Resistance: A nominal value of 60.0 Ohms, indicating low energy loss within the resonator.
• Drive Level: It is rated for a drive power between 16.0 mW (minimum) and 24.0 mW (maximum).
• Shunt Capacitance: Maximum permissible shunt capacitance is 7.0 picofarads (pF).

Physical Specifications:

The unit features an OVAL BODY design with PIN TERMINALS. Its construction adheres to strict dimensional controls necessary for interchangeability and mounting integrity:

• Overall Length: 1.023 inches maximum.
• Body Width: 0.725 inches maximum.
• Terminal Diameter: 0.048 to 0.052 inches.
• The holder cover material is specified as METAL.

Manufacturing and Specification Lineage

This part is tied closely to military specifications, indicated by its cross-reference to MILC3098-31. The primary manufacturing source identified via the Cage Code 81349 belongs to MILITARY SPECIFICATIONSPROMULGATED BY MILITARY, suggesting adherence to stringent defense standards (such as MIL-PRF specifications).

The consistency required for defense and aerospace applications necessitates standardized components. This quartz crystal unit, with its NIIN 00-068-1300, is a recognized component within critical timing systems where precision at high temperatures is non-negotiable.

Real-World Application Context

Quartz crystal units operating at 68.778 MHz are typically found serving as the reference clock source in sophisticated electronic systems. Applications often include:

1. Secure Communications Gear: Providing stable carrier frequencies for radio transmitters and receivers, ensuring signal integrity over long distances.
2. Navigation Equipment: Forming the basis of time measurement circuits in ruggedized GPS receivers or inertial navigation platforms where environmental resilience (up to +105°C) is essential.
3. Test and Measurement Instruments: Serving as a high-stability reference oscillator in military-grade spectrum analyzers or signal generators that must maintain calibration fidelity under varying field conditions.

The availability of numerous alternate parts—including MILC309831 and CR53AU68.778000MHZ—highlights the importance of this specific frequency and form factor across various procurement channels.