Field Measurements & Troubleshooting Flow

This quick-reference guide helps troubleshoot HF dipoles using real-world measurements, feed-line comparisons, and a practical field workflow.

Shop‑Ready Measurement Examples (20m Half‑Wave Dipole)

Example	Feedline	Rig‑Side R (Ω)	Rig‑Side X (Ω)	Rig‑Side SWR	Notes
A Well Tuned	20–30 ft LMR‑400	≈ 48–55	≈ ±0–10	≈ 1.05–1.30	Feedpoint ≈ 50 + j0 Ω
B Lossier Line	30 ft RG‑8X	Similar resonance	Similar	May appear “better”	Expect 0.5–1.0 dB more loss vs LMR‑400. Lossy coax can hide true SWR.

Page Troubleshooting Flow

• Calibrate analyzer using open / short / load.
• Measure directly at the feedpoint first.
• Record R, X, and SWR at the operating frequency.
• Measure again at the rig with the installed feedline.
• Clamp a current probe at the feedpoint and shack entry.
• If common‑mode current is present, add a choke and re‑test.
• Inspect connectors, weatherproofing, and strain relief.
• Trim or length‑adjust elements to center resonance if needed.

HF Dipole Recommended Choke

Use a 9–12 turn FT‑240‑43 ferrite choke or equivalent at the feedpoint and/or shack entry to reduce common‑mode current on the coax shield.

Pass / Fail Thresholds

• Feedpoint SWR > 2:1 → trim or length‑adjust the dipole elements.
• Rig‑side SWR > 1.8:1 with low‑loss coax → verify feedpoint mismatch.
• Clamp current > ~0.2 A RMS at shack entry → add or relocate choke(s).
• Lossy coax can make SWR readings appear better than reality.

Target values near band center: R ≈ 50 Ω and X ≈ 0 Ω.

HF Dipole Field Tips

• Document coax type and total feedline length.
• Keep the feedpoint centered and mechanically balanced.
• Weatherproof all outdoor connections.
• Use low‑loss coax whenever possible for accurate readings.
• Recheck measurements after each change.