Coax Cable Delay Calculator

Overview

The Coax Cable Delay Calculator computes one-way and round-trip propagation delay (nanoseconds), guided signal velocity, wavelength in cable (lambda_c), electrical length (lambda), and RF phase shift for coaxial transmission lines. Essential for phased array feed networks, antenna phasing harnesses, and high-speed digital clock alignment.

Input Guide

Enter Cable Length exactly as shown on the calculator. Confirm every unit, selected option, and decimal position before calculating so the coax cable delay result matches the intended transmission lines design case.

Output Guide

The output section reports One-Way Propagation Delay, Round-Trip Delay, Delay per Metre, Propagation Velocity, Velocity Factor, Wavelength in Cable, Quarter-Wave Length, Half-Wave Length, Electrical Length, Total Phase Shift, Normalized Phase Shift, Design Note for the values you entered. Use these values as design targets, then compare them with available space, component limits, feed system behavior, installation environment, and measured performance before finalizing the design.

How This Calculator Works

The Coax Cable Delay applies Velocity = c × VF, Delay = Length / (c × VF), Phase = 360° × f × Delay, lambdac = (c × VF) / f to the entered values. Calculate one-way propagation delay, round-trip delay, propagation velocity, wavelength in the cable, electrical length, and RF phase shift for a coaxial cable. Use the result as a first-pass transmission lines target, then validate it against losses, tolerances, mounting, nearby conductors, feed-line effects, and measurement conditions.

Design Notes

RF signals travel slower through coaxial cables than through free space due to the relative dielectric constant (epsilon_r) of the insulating material (VF = 1 / sqrt(epsilon_r)). Solid polyethylene (PE) dielectrics yield a velocity factor of VF approximately 0.66 (approximately 5.06 ns/m delay), foam polyethylene achieves VF approximately 0.80--0.85 (approximately 3.9--4.1 ns/m delay), and PTFE (Teflon) ranges between 0.69 and 0.88. Accurate delay matching is critical in phased arrays and TDR (Time Domain Reflectometry) cable fault detection.

Build and Tuning Notes

When building phase-matched cable pairs or delay lines, measure actual velocity factor (VF) using a Vector Network Analyzer (VNA) or Time-Domain Reflectometer (TDR) rather than relying solely on manufacturer nominal datasheet values. Cable temperature fluctuations and mechanical bending radii alter physical cable propagation delay and phase stability.