What Is a Coaxial Cable?
A coaxial cable is a cable that surrounds a center conductor with insulation and encircles it with an outer braided shield, carrying high-frequency signals with low loss.
Its Structure
From inside out: the center conductor, insulation (dielectric), a braided/foil shield and the outer jacket. The center carries the signal; the shield is both the return path and a shield against external interference.
Impedance
A coaxial cable's characteristic impedance (usually 50Ω or 75Ω) is fixed. This lets the signal travel without reflection; it must be the same impedance as the connected RF connector and device.
| Impedance | Use |
|---|---|
| 50Ω | RF, Wi-Fi, radio, measurement |
| 75Ω | TV/video, antenna, satellite |
Why Shielded?
The outer shield protects the cable against external electrical noise and stops the high-frequency signal inside from radiating out. So it's indispensable in RF transmission.
Where Is It Used?
Antenna/satellite downleads, Wi-Fi/radio antennas, cable TV, oscilloscope probes and RF measurement/communication lines.
Loss (Attenuation)
Every coaxial cable attenuates the signal somewhat, and this loss increases as the frequency rises and the cable lengthens. So on high-frequency and long lines a thicker, low-loss cable is preferred; a needlessly long cable drops the signal level significantly.
Common Mistakes
- Impedance mismatch: mixing 75Ω instead of 50Ω causes reflection/loss.
- Sharp bend: bending the cable too much spoils the impedance.
- Bad connector: a faulty termination causes signal loss.
Frequently Asked Questions
What's the difference between 50Ω and 75Ω?+
Why won't a normal cable do?+
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