Engineering Reference for Connector Series, Electrical, Mechanical, and Environmental Specifications
1. MIL-PRF-39012 Specification Framework & Classification
MIL-PRF-39012 establishes the general performance and qualification requirements for radio frequency (RF) coaxial connectors. All connectors covered under this specification dataset belong to Class 2—connectors intended to provide mechanical connection within an RF circuit providing defined electrical and RF performance. Connectors are further categorized by assembly and field serviceability methods:
- Category A: Field serviceable connectors requiring no special tools for assembly (assembled using standard wrenches, pliers, and soldering equipment).
- Category B: Non-field replaceable connectors intended exclusively for original equipment (OEM) installation. Government stocking/procurement is prohibited.
- Category C: Field replaceable connectors requiring standard military crimping tools (SAE AS22520) and standard cable stripping dimensions with solder center contacts.
- Category D: Field replaceable connectors requiring standard military crimp tools for both center contact and outer ferrule, conforming to standard cable stripping dimensions.
2. RF Coaxial Connector Series Technical Specifications
The table below summarizes key mechanical, electrical, and operating properties across the 7 major MIL-PRF-39012 coaxial series contained in the specification library:
| Series | Coupling Type | Freq. Range | Working Voltage | Max VSWR | Engineering Applications & Notes |
| Series BNC | Bayonet | 0 – 4 GHz | 500 V rms (sea level) 125 V rms (70,000 ft) | 1.30 | Quick-connect bayonet coupling for lab equipment, video, and low-power RF interconnects. |
| Series TNC | Threaded (.4375-28) | 0 – 11 GHz | 500 V rms (sea level) 125 V rms (70,000 ft) | 1.30 | Threaded version of BNC designed for high-vibration avionics and tactical radios. |
| Series C | Bayonet (Two-Stud) | 0 – 11 GHz | 1,000 V rms (sea level) 250 V rms (70,000 ft) | 1.35 | Medium-size weatherproof bayonet connector for medium-power outdoor RF systems. |
| Series SC | Threaded (.6875-24) | 0 – 11 GHz | 1,000 V rms (sea level) 250 V rms (70,000 ft) | 1.30 | Threaded version of Series C providing constant 50Ω impedance under severe shock. |
| Series N | Threaded (.625-24) | 0 – 11 GHz | 1,000 V rms (sea level) 250 V rms (70,000 ft) | 1.30 | Medium-size threaded connector for high-power transmitter feeds, radar, and cellular base stations. |
| Series SMA | Threaded (.250-36) | 0 – 12.4 GHz (Flex Cable) | Cable-Dependent (e.g., RG-58 / RG-142) | 1.30 | Subminiature high-density connector for aerospace microwave electronics and radar front-ends. |
| Series SMB | Snap-On | 0 – 4 GHz | 250–335 V rms (sea level) 60–85 V rms (70,000 ft) | Cable-Dep. | Subminiature snap-on coupling for rapid chassis/PCB inter-module RF patching. |
3. Environmental Resistance, Sealing, and Hermetic Properties
MIL-PRF-39012 connectors undergo rigorous environmental and sealing qualification tests to ensure reliability in military and aerospace operational environments:
| Property / Test | Test Standard / Condition | Specification Requirement | Engineering Significance |
| Pressurized Sealing | 30 psi (30 lbf/in²) air pressure for 30 sec to 2 min (capped mating end) | No mounting seal air leakage | Evaluates panel-mounting jam-nut/flange gaskets in pressurized bulkheads. |
| Hermetic Sealing | MIL-STD-202 Method 112 (Helium tracer gas at 1 atm differential) | Leakage ≤ 1×10⁻⁵ cc/s (Series C/TNC) ≤ 1×10⁻⁷ cm³/s (Series N) | Fused glass-to-metal seals for vacuum, space, and hermetically sealed avionics enclosures. |
| Thermal Operating Range | MIL-STD-202 Method 107, Condition B (-65°C to +165°C / +200°C) | No mechanical damage or electrical degradation | High-temp +200°C rating applicable when mated with PTFE/FEP Fluorocarbon cables. |
| Corrosion, Shock & Vibration | Salt Spray: MIL-STD-202-101 (Cond B) Shock: MIL-STD-202-213 (50G) Vibration: MIL-STD-202-204 (Cond B/D) | No cracking, flaking, or electrical discontinuity permitted | Guarantees structural integrity under harsh marine, combat, and flight environments. |
4. Summary of Electrical Performance Limits
Key electrical baseline criteria across MIL-PRF-39012 class 2 connectors include:
- Insulation Resistance: 5,000 MΩ minimum initial per MIL-STD-202 Method 302 Condition B; maintains at least 200 MΩ within 5 minutes after moisture resistance exposure.
- Dielectric Withstanding Voltage (DWV): 1,500 V rms sea level for BNC/TNC/SMB; 2,500 V rms for Series N; 3,000 V rms for Series C per MIL-STD-202 Method 301.
- Corona Level & Altitude Performance: Corona extinction voltage at 70,000 feet altitude is rated at 375 V rms for BNC/TNC/SMB and 750 V rms for Series C/N.
- RF Leakage & Insertion Loss: Series C provides -55 dB minimum RF shielding (2–3 GHz) with ≤ 0.10 dB insertion loss at 4 GHz. Series TNC provides -60 dB shielding (2–3 GHz) with ≤ 0.21 dB insertion loss at 9 GHz.