How do I select the right coaxial cable type for a given frequency, loss, and power handling requirement?
Coaxial Cable Selection Guide
The coaxial cable market offers hundreds of types spanning a vast range of performance, flexibility, and cost. Selection starts with the non-negotiable requirements (frequency range, connectors, physical constraints) and then optimizes the negotiable parameters (loss, phase stability, cost).
| Parameter | Semi-Rigid | Conformable | Flexible |
|---|---|---|---|
| Loss (dB/m at 10 GHz) | 0.8-2.5 | 1.0-3.0 | 1.5-5.0 |
| Phase Stability | Excellent | Good | Fair |
| Bend Radius | Fixed after forming | Hand-formable | Continuous flex OK |
| Shielding (dB) | >120 | >90 | >60-90 |
| Cost (relative) | 2-5x | 1.5-3x | 1x |
- Performance verification: confirm specifications against the application requirements before finalizing the design
- Environmental factors: temperature range, humidity, and vibration affect long-term reliability and parameter drift
- Cost vs. performance: evaluate whether the application demands premium components or standard commercial grades
Frequently Asked Questions
What cable do I use for a VNA setup?
Use phase-stable test cables designed for your frequency range. Sucoflex 104 or Gore Phaseflex to 26 GHz. Sucoflex 126 to 70 GHz. These cables have phase stability of < 5°/GHz over the flex range, which is essential for accurate S-parameter measurement after calibration.
Does cable length matter?
Loss per unit length matters most. At 10 GHz: 0.141-inch semi-rigid loses about 0.3 dB/foot. A 6-foot cable loses 1.8 dB, which may be acceptable for a transmitter feed but excessive for a receiver front end. Keep cables as short as possible in loss-sensitive applications.
What about plenum-rated cables?
Plenum cables use low-smoke, low-flame materials for the jacket and dielectric, meeting fire codes for installation in building air ducts. Plenum-rated RF cables are available but typically have 10-30% higher loss due to the dielectric material changes. Use them only where building codes require it.