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Impedance, SWR & Feedline Loss Reference Tables

This reference page provides important tables and reference values for feedline performance and matching requirements in amateur radio systems. Whether you’re using coax, ladder line, or other transmission line types, understanding impedance, Standing Wave Ratio (SWR), and expected losses will help you build efficient, reliable stations.

Standard Impedance Values

Most ham-radio feedlines and antennas are designed for a nominal 50 ohm impedance. Balanced lines such as ladder line may use 300 or 450 ohms nominal impedance depending on manufacturer specs. Always match transmitter, feedline, and antenna impedance to minimize reflections.

Typical SWR & Reflection Reference

An ideal match provides minimal reflections and SWR close to 1:1. Below is a standard reference:

  • 1:1 to 1.5:1 — Excellent match, minimal loss
  • 1.5:1 to 2:1 — Acceptable match, small loss increase
  • 2:1 to 3:1 — Useable for narrow-band, but expect noticeable loss
  • Above 3:1 — Typically signals reflection, high loss — retune antenna or use matching network

Feedline Loss Reference by Type & Length

The following are example loss estimates for common feedlines (loss values vary by frequency, construction, and condition):

  • RG-8 / RG-213: Moderate loss — acceptable for short runs or HF work
  • LMR-400 / Foam-dielectric coax: Lower loss — better for longer runs or higher frequencies
  • Balanced line (ladder/open-wire): Very low loss when properly matched and installed

Using Reference Tables Effectively

Use the tables to estimate:

  • Feedline loss for given length and frequency
  • Needed antenna length based on impedance and SWR expectations
  • Whether your current feedline is suitable for power level and operating band

Summary

Matching impedance, maintaining low SWR, and choosing the proper feedline type and length are key to efficient station design. Use these reference values and tables as a baseline — always verify with measurements after installation for best results.

Continue exploring related guides in the Feedline and Quick Reference sections for connectors, weatherproofing, antenna matching and installation best practices.