Cable Loss Calculator

Before measuring a DUT through a cable, it helps to know how much loss the cable itself introduces. This calculator estimates total loss, loss per unit length, electrical length, and power delivery for common coaxial cable types.

Cable Loss Estimator

Cable Type RG-58 RG-8X RG-213 RG-8/U LMR-240 LMR-400 RG-174 RG-6 (75Ω) RG-11 (75Ω) Hardline 1/2"

Length

ft

Frequency (MHz)

-- Total Loss (dB)

-- Loss per 100 ft

-- Impedance (Ω)

-- Velocity Factor

-- Electrical Length (°)

-- Wavelengths (λ)

Power Delivery (100 W input) --

Delivered Lost as heat

How Cable Loss Works

Coaxial cable loss comes from two mechanisms:

1. Conductor loss — resistive heating in the center conductor and shield, proportional to √f
2. Dielectric loss — energy absorbed by the insulator, proportional to f

At HF and VHF frequencies (where NanoVNA-H operates most often), conductor loss dominates. That is why the calculator uses a √f interpolation model — it fits manufacturer data points by assuming loss scales with the square root of frequency.

Note

The √f model is accurate within a few percent for most cables up to 1 GHz. Above that, dielectric loss becomes significant and the model slightly underestimates total loss.

Using Cable Loss Data with NanoVNA-H

Compensating S21 Measurements

When measuring a device (filter, amplifier, attenuator) through test cables:

1. Calculate the total loss of your test cables using this calculator
2. Subtract the cable loss from your measured S21 to get the true device performance
3. Better yet — calibrate with the cables in place so the NanoVNA-H removes cable effects automatically

Validating Cable Measurements

Use this calculator as a sanity check against NanoVNA-H cable loss measurements:

1. Measure cable loss with the NanoVNA-H using the Cable Loss tutorial
2. Compare with the calculator estimate for the same cable type and length
3. If the measured loss is significantly higher, the cable may be damaged

Choosing Test Cables

For measurements above 500 MHz, cable loss matters. A 3-foot RG-174 jumper at 1 GHz loses about 1.5 dB — enough to affect dynamic range. Use the calculator to pick cables that keep total test setup loss under 1 dB.

Cable Selection Guide

Application	Recommended Cable	Why
Bench test jumpers (< 300 MHz)	RG-58	Flexible, cheap, adequate loss
Bench test jumpers (> 300 MHz)	RG-8X or LMR-240	Lower loss, still flexible
Antenna feedline (HF)	RG-213 or RG-8/U	Low loss at HF, handles power
Antenna feedline (VHF/UHF)	LMR-400	Significantly lower loss
Tight spaces / mobile	RG-174	Very flexible, but high loss

Tip

The velocity factor shown in the results is useful for cutting cables to specific electrical lengths — a common task when building phasing harnesses or delay lines.

Related Guides

• Cable Loss Measurement — measure actual cable loss with NanoVNA-H
• Cable TDR — find faults and measure physical cable length
• Time Domain Transform — understanding TDR mode