Transmitting Loops
Overview
Transmitting loops divide into two structurally distinct families: small magnetic transmitting loops (Alexloop, Chameleon F-Loop, Ciro Mazzoni, MFJ-1786/1787/1788 series) — high-Q magnetic radiators tunable across HF by a variable capacitor, 1–2 m diameter, 1–2% instantaneous bandwidth — and full-wave loops (delta, quad, square, hex beam) that behave as resonant current-element antennas with dipole-class bandwidth and pattern. This dive covers the magnetic-vs-electric radiator physics (the three loop-size regimes by λ-fraction), the variable-capacitor tuning requirement, the 5 kV capacitor-voltage rating at 100 W, the hex beam as the directional full-wave member, and the DIY build (a 1 m diameter HF magloop with a butterfly capacitor). Commercial buys are ranked from Chameleon to Ciro Mazzoni.
Context
The small magnetic transmitting loop is the stealth HF antenna — the right choice for HOA-restricted properties, apartment balconies, attic installations, and hotel-room portable operation where a visible dipole or vertical is impossible. Its severe instantaneous bandwidth limitation (1–2% per band, requiring constant retuning across each QSY) is the cost; the compact form factor (1–2 m diameter for HF) and deep tolerance for low mounting heights and ground proximity are the payoff. The receive-only loop cousins — K9AY, beverage, terminated flag/pennant, active Wellbrook-type loops — live in the companion Receive-Only Loops sub-project; those are SNR-optimization antennas, not radiators.
