Estimate velocity factor, wavelength, delay, and electrical length. Model transmission behavior using practical inputs. Support faster design decisions with reliable cable calculations.
Velocity factor is the wave speed in a medium divided by the speed of light in vacuum.
| Material / Cable | Dielectric Constant | Approx. Velocity Factor | Frequency (MHz) | Line Wavelength (m) |
|---|---|---|---|---|
| Foam PE Coax | 1.50 | 0.8165 | 100 | 2.447 |
| Solid PE Coax | 2.25 | 0.6667 | 100 | 1.999 |
| PTFE Cable | 2.10 | 0.6901 | 250 | 0.827 |
| Twin Lead | 1.70 | 0.7670 | 50 | 4.599 |
Velocity Factor: VF = v / c
Wave Speed from Dielectric Constant: v = c / √εr
Velocity Factor from Dielectric Constant: VF = 1 / √εr
Velocity Factor from Wavelengths: VF = λline / λfree-space
Wavelength in Line: λline = v / f
Electrical Length: θ = (L / λline) × 360
Delay per Meter: delay = (1 / v) × 109 ns
Where c is the speed of light, v is propagation speed, εr is relative permittivity, f is frequency, and L is cable length.
Choose a calculation mode first. Use dielectric constant for material-based estimation, wavelength ratio for measured line behavior, delay for time-domain measurements, or direct speed when propagation velocity is already known.
Enter the operating frequency and cable length. Then fill the remaining fields required by your selected mode. Press the calculate button to display results above the form.
Review velocity factor, propagation speed, wavelength in the line, electrical length, and delay values. Use the CSV and PDF buttons to save the current result set.
Velocity factor shows how fast a signal travels through a cable compared with light in vacuum. A value of 0.66 means the signal moves at 66% of light speed.
Higher dielectric constant slows electromagnetic propagation. Since wave speed falls as permittivity rises, the resulting velocity factor becomes smaller.
For normal transmission lines and cables, no. Physical propagation speed inside the medium stays below the speed of light in vacuum.
Electrical length determines phase shift along a line. It matters in impedance matching, resonant sections, filters, antennas, and RF measurement setups.
Use delay mode when you have measured travel time from instrumentation, pulse tests, or reflectometry and want to derive propagation speed and velocity factor.
Not always. Many cables stay close over wide ranges, but dispersion, construction, and dielectric losses can cause small frequency-dependent changes.
Typical values range from about 0.66 for solid polyethylene dielectric to around 0.80 or higher for foam dielectric constructions.
Yes. It helps estimate wavelength in the feed line, phase shift, and delay, which are useful for cable stubs, matching sections, and timing checks.
Important Note: All the Calculators listed in this site are for educational purpose only and we do not guarentee the accuracy of results. Please do consult with other sources as well.