RF Transmission Engineering
Coaxial Cable Fundamentals
Coaxial cable is the primary transmission medium for Radio Frequency (RF) signals, high-definition video (CCTV/HD-SDI), and satellite communications. Unlike standard low-voltage cables, coaxial performance is governed by characteristic impedance (usually 50Ω or 75Ω) and frequency-dependent attenuation.
As frequency increases, signals travel closer to the surface of the conductor (the Skin Effect), leading to higher resistance and attenuation. This is why a cable that works perfectly for analog CCTV (low frequency) might fail completely for satellite L-band signals (high frequency).
Impedance Matching
50 Ohms (RF & Wireless)
Standard for wireless transmitters, two-way radios, and mobile networks. Provides high power handling and low loss for transmit applications (LMR-400, RG8, RG58).
75 Ohms (Video & CATV)
Optimized for low attenuation and high-quality signal reception. Used for satellite, cable TV, and professional video monitoring (RG6, RG11, RG59).
Velocity Factor & Dielectrics
The Velocity Factor (VF) indicates how fast signals travel through the cable compared to the speed of light in a vacuum. A VF of 0.85 means the signal travels at 85% of c. This is critical for time-sensitive applications like GPS synchronization or phase-matched antenna arrays.
Propagation Delay (ns) = Cable Length / (c × VF)