Search results

A helically wound two element 40 meter yagi beam antenna from a 1974 QST article

JJ0DRC's HF multi-band delta loop antenna project, initially conceived during the waning peak of Cycle 23, addresses the common challenge of achieving effective DX operation from a small residential lot in Japan. Dissatisfied with a ground plane antenna's performance in SSB pile-ups, the author sought a beam-like solution without a tower, drawing inspiration from a JJ1VKL article in CQ Ham Radio Sep. 2000. The antenna, constructed in October 2000, employs two 7.2-meter fishing rods (37% carbon fiber, reinforced with cyano-acrylate glue and aluminum tape) and 1mm enameled wire, fed by an Icom AH-4 external antenna tuner. While the exact beam pattern remains unmeasured, JJ0DRC observed a significantly higher callback rate compared to dipole antennas, particularly on higher bands. The system's circumference length of 15-20m is crucial for maintaining a good beam pattern across HF bands, though performance on lower bands like 80m, 40m, and 30m becomes less directional as the length deviates from a full wavelength. Ongoing maintenance addressed degradation issues, including aluminum tape cracking and wire breakage at connection points due to strong winds (often exceeding 10-15m/s in winter). The author reinforced rod connections with IRECTOR PIPE SYSTEM components and INSU-ROCK ties, and improved wire attachment methods using Cremona rope and epoxy bond to enhance durability.

A well documented article on a small magnetic loop antenna for the 40 meters band

A portable (15.5 foot diameter) NVIS loop for 3.5 to 7.3 MHz. Performs well at high and low takeoff angles, and has smaller footprint than most NVIS antennas.

A small magnetic loop antenna, often employed by hams facing antenna restrictions or high local RFI, offers a compact solution for HF operation. This resource details the construction of a foldable magnetic loop designed for the 40m through 17m bands, emphasizing its high-Q factor and _Faraday coupling_ for effective noise rejection and narrow-band filtering. The guide outlines material selection, advocating for copper over aluminum to maximize efficiency, and provides insights into the physics governing its operation, including impedance matching and resonance principles. Practical application of this antenna design is particularly beneficial for QRP enthusiasts and portable operators seeking a stealthy, high-performance antenna. The construction process includes specific details for a 1-meter diameter loop, a 140pF variable capacitor, and a _gamma match_ for impedance transformation. Performance comparisons suggest that while a full-size dipole might offer slightly better gain, the magnetic loop's ability to mitigate local noise often results in a superior signal-to-noise ratio, making it a viable option for challenging RF environments.

The small receiving loop (SRL) is a versatile and efficient antenna that can be simply built from common materials. It is designed for reception on the MF and HF bands and may be put in a variety of shapes and sizes. Despite its unusual installation, the porch loop in this case operated admirably, producing several DX spots on the 40m band. The SRL can be a great option for people looking to boost their reception on the MF and LF bands.

The POCKET TUNER V1.1 is a highly compact HF T-Match antenna tuner designed for QRPp and QRP portable operations. With a credit card-sized form factor, it is tailored for low-power setups, supporting HF bands from 10m to 40m. The tuner features a unique design using rotary switches for precise capacitor adjustments, allowing tuning in small increments. Its inductance selection is optimized for various bands, ensuring efficient performance. Equipped with a resistive tuning indicator, it protects the transmitter by reducing SWR during adjustments. This versatile and portable tuner is ideal for field operations, enabling efficient antenna matching for low-power rigs.