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Harmonic Relationship Table

How to read this table and Fundamental (MHz) 2nd Harmonic (MHz) 2nd Overlaps 3rd Harmonic (MHz) 3rd Overlaps 4th Harmonic (MHz) 4th Overlaps 160 m 1.800–2.000 3.600–4.000 80 m 5.400–6.000 — 7.200–8.000 40 m 80 m 3.500–4.000 7.000–8.000 40 m…

Understanding Harmonics on the HF Amateur Radio Bands

Harmonics are an unavoidable byproduct of RF generation. Every HF transmitter—no matter how modern or well-filtered—produces harmonic energy at integer multiples of its fundamental frequency. On the HF bands, these harmonics have both theoretical significance and practical operating consequences, particularly…

APRS: The Original Internet of Things for Ham Radio

Long before smartphones tracked our every move and apps pinged our location to friends, ham radio operators created something remarkable: a system that could track vehicles, report weather conditions, send messages, and share telemetry data—all without the internet, cell towers,…

Ferrite core selection charts

A. Which mix to use (HF-focused) Mix Best general region Typical “why” Practical guidance Mix 31 ~1–30 MHz Excellent for choking common-mode on HF; good broadband behavior Best first choice for chokes and many broadband transformers Mix 43 ~5–50 MHz…