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An homemade portable vertical antenna with a trap near the mid point of the main element. The trap is made with 42mm diameter PVC pipe with 9 turns of wire on it

An HF multiband trapped antenna in french

The 60-page PDF document, "Antenna Systems and Theory For The Non-Technical Ham" by Jim Abercrombie, N4JA, provides a foundational understanding of antenna systems. It explains basic antenna theory, including how antennas work, electromagnetic wave polarization, and the role of frequency. The resource details various antenna types such as flat top dipoles, inverted-V dipoles, shortened loaded dipoles, G5RV dipoles, Carolina Windoms, and end-fed configurations. Vertical antennas, including ground-mounted trapped verticals and inverted-L verticals, are also covered. Directional beam antennas like monoband Yagis, cubical quads, and log-periodic arrays are discussed. Propagation modes, including ground-wave, direct wave, and skywave propagation, are explained in detail, with specific attention to the D, E, and F layers of the ionosphere and their effects on HF communication. Technical concepts such as standing wave ratio, decibels, resistance, and reactance are defined, along with calculations for half-wave resonant dipole lengths. The document addresses feed-line radiation, balun applications, and critical antenna and tower safety considerations. It aims to dispel common antenna myths and educate hams on making informed antenna choices.

This antenna is an omnidirectional and multiband and it is well suited for DX enthusiasts with limited space. Each of the parallel circuits (trap) behaves like an isolator on its resonant frequency.

Building an 80-160 meter antenna in a small garden (9m x 14m) involves creative solutions due to space constraints. This project outlines the construction of a trapped 80-160 meter vertical dipole, utilizing a crank-up tower and an 11-meter fiberglass pole. The design prioritizes minimal visibility, ease of construction, and cost-effectiveness, achieving effective operation despite limited space.

This PDF document provides detailed information on the design, construction, and tuning of trapped vertical antennas with radials for ham radio operators. It covers the theory behind trapped antennas, practical considerations for installation, and tips for optimizing performance. Whether you are a beginner looking to build your first HF antenna or an experienced operator seeking to improve your station setup, this guide offers valuable insights and instructions. By understanding the principles outlined in this document, hams can enhance their operating experience and make the most of their radio communication capabilities.