Meaning
Signal power reduction occurs as electromagnetic waves travel through a shielded transmission line. The coaxial attenuation determines how much of the original input remains at the output terminal after passing through a specific length of cable. Loss is measured in decibels per unit length at a given frequency.
Values increase as the operating frequency rises due to skin effect and dielectric heating.
Conductor Loss
Resistance within the copper or silver plating converts electrical energy into heat. In the context of coaxial attenuation, the skin effect forces current to flow near the surface of the conductor at high frequencies, which increases the effective resistance. Larger center conductors reduce this effect by providing more surface area.
Braided shields contribute more loss than solid foil layers. Silver plating is frequently applied to reduce the resistance of the outer skin.
Dielectric Absorption
Molecular friction within the insulating layer between the conductors saps signal strength. High-grade teflon or expanded foam minimizes the coaxial attenuation by keeping the dissipation factor low. Lower quality plastics absorb more energy and convert it to heat.
This mechanism is the primary driver of loss in the gigahertz range.
Environmental Sensitivity
Temperature fluctuations alter the physical properties of the cable materials. Rising heat increases the resistance of the metal and the molecular activity of the insulator, which worsens the coaxial attenuation. Cables intended for outdoor or aerospace use must be rated for these changes.
Moisture ingress into the braid also causes a rapid spike in signal loss.
