Search results

A self-supporting vertical antenna design for stationary-mobile HF-VHF operation is presented, emphasizing ease of construction with common materials like a fiberglass fishing rod and PVC pipe. The design focuses on creating a set of no-tuner monoband radiators for bands such as **2m**, **6m**, 10m, and 12m, with an overall radiator support length of 3.3m. The construction process details the assembly of the antenna base using a magnetic mount, PL-259 connector, and PVC pipe sections, which then supports the telescopic fishing rod. Radiator extensions are cut to achieve quarter-wave resonance on specific bands, with detailed instructions for 6m (50-51 MHz), 10m (28.5 MHz), and 12m (24.9 MHz). For lower HF bands like 15m, 17m, and 20m, the design incorporates base-loading coils, with specific turn counts provided (e.g., 21 turns for 20m). The project also suggests using an _antenna analyzer_ for precise tuning of extensions and coils, moving beyond theoretical values to achieve optimal performance. The author, _IK1ZYW_, notes that for 80m and 160m, the antenna becomes less efficient as a vertical, suggesting alternative configurations like an inverted-V dipole or asymmetrical inverted-L.

The Antenna Rotator Controller is unique in that it senses, displays, and controls to the earth's true magnetic field. The compass sensor, mounted in a waterproof enclosure, is attached to the mast and sends its signal to a microcontroller

Presents the Light Loop, a small magnetic loop antenna optimized for 40m through 10m operation, demonstrating its construction for portable QRP use. The design emphasizes lightweight materials and a compact form factor, making it suitable for handheld or backpack deployment during field activities. It details the primary radiating element, the coupling loop, and the variable capacitor required for resonance across the specified HF bands. The article provides specific component choices, such as the 1.5-inch diameter aluminum tubing for the main loop and the 10-365 pF variable capacitor for tuning. It discusses the importance of precise loop circumference and spacing for efficient impedance matching and bandwidth characteristics. The resource includes practical advice on achieving resonance and optimizing performance for low-power transceivers. Construction notes cover the mechanical assembly, including mounting the capacitor and feedpoint connections. It highlights the antenna's suitability for pedestrian mobile operations, offering a practical solution for HF communication without extensive setup. The design aims for a balance between portability and effective radiation on the lower HF bands.

An invisible magnetic loop antenna mounted under a table by PY1AHD

A homebrew Magmount for 2m antenna

A NEC Model Comparative Analysis of Physical Orientation and Performance. The small magnetic loop is a useful compromise antenna for limited space and portability. For this reason, the magnetic loop antenna is a practical high frequency antenna solution for the restricted space of apartment dwellers

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.

I wanted to mount an amateur radio antenna on my truck that was more permanent than the magnetic mount on I already had, but I had a few specific design requirements for the project.

High-performance rugged antennas and RF accessories such as magnetic mounts, RF coaxial gooseneck adapters, LNAs, BDCs, for law enforcment, military, maritime and video markets.

DL7JV shares his practical experience building and testing capacitive antennas, initially skeptical of their performance compared to magnetic loops and mono-band dipoles. His interest was piqued after hearing a Spanish station running 100 Watts on 80 meters with a 1-meter Micro Vert, making DX contacts into PY and UA0, despite the antenna being only 4 meters high in a garden. This prompted DL7JV to investigate further, consulting resources from DL7PE and DL7AHW, the latter providing DOS programs like "Mitspule.exe" and "Spulenprg.zip" for calculating antenna dimensions and coil conversions. The article outlines the construction of two prototype antennas: one for 7.050 MHz using a 75mm PVC pipe and another for 3.550 MHz with a 110mm PVC pipe. Both designs feature aluminum foil condensers and coils wound from 1mm² H07V-K wire. DL7JV provides specific measurements for the condenser capacitance, surface area, diameter, height, coil inductance, turns, and wire length for both 40m and 80m versions, along with RG58 feedline lengths. Initial reception tests for the 7 MHz antenna, placed indoors, yielded impressive S9+5 signals from a German station compared to an S8 from a 42-meter roof-mounted loop, even hearing a Japanese station. Transmission attempts on April 4, 2004, despite moderate solar storm conditions, resulted in successful QSOs on 7 MHz with EA5OT (579/559) and on 3.5 MHz with YT1NT (579/559) and G4KKI (579/559) using 100 Watts. DL7JV notes the antenna's sensitivity to coordination and feedline layout, suggesting a modification from DL7AXO involving a 500pF fixed capacitor and coil tap for improved SWR stability. He concludes that while the capacitive antenna is space-saving and performs well for reception and 100W transmission indoors, its transmit performance doesn't yet match larger antennas, with further outdoor field tests planned. DL7JV also intends to build a 1.8 MHz version.

A distance of 1/8 lambda between the antenna and the vehicle roof is suggested for optimal performance, with slight adjustments possible to lower the take-off angle for terrestrial contacts. This resource details the adaptation of an _Eggbeater_ antenna for mobile use, specifically for VHF operation, leveraging the car's metal roof as a ground plane. It illustrates the mounting method, repurposing a magnetic ski carrier base, and describes the integration of coaxial relays for polarization reversal, a feature also applicable to UHF versions as discussed in "_Eggbeater Antenna VHF/UHF – Part 2_". This mobile configuration proves effective for satellite communications, such as through the International Space Station (ISS), while also maintaining strong performance for land-based radio contacts. The inclusion of switches with indicator lights for VHF and UHF polarization control, powered by the vehicle's battery, highlights practical considerations for field deployment. The system's adaptability for portable operations underscores its versatility beyond fixed mobile installations.

7MHz to 30MHz operation is achieved with a magnetic-mounted HF antenna designed for car roof deployment, capable of handling 100 Watts without an external antenna tuner. The design incorporates a large base-loading coil with multiple taps, allowing for frequency selection across various HF bands. This coil effectively increases the electrical length of a short telescopic antenna element, compensating for its inherent capacitance. Construction involves 3D-printed components for the coil former and support structures, though conventional building methods using plastic drainpipes are also suggested. The car body serves as the ground plane, with the coil assembly mounted on a 500mm square metal plate secured by super neodymium magnets. Protection under the magnets is advised to prevent vehicle scratches. Detailed instructions cover winding the 30-turn coil with 2.5mm diameter household electrical cable, assembling the 3D-printed parts, and making soldered connections. Taps are staggered every five turns for precise frequency adjustment. Performance examples include a 7913km contact to Japan using a 1.5m element and 100 Watts, demonstrating low-angle radiation and omni-directional pattern with minimal S-point loss compared to a full quarter-wave.

Optimizing directional gain on the 40-meter band often involves complex antenna designs; this resource details the construction and performance of a reversible _Moxon_ array. The design provides directional coverage from southeast to west, with a switching mechanism to reverse the pattern towards east to northwest. Key design considerations include precise element spacing, the critical role of coil inductance for proper resonance, and the use of _NEC5_ for accurate electromagnetic modeling, ensuring the antenna performs as predicted across the desired frequency range. The antenna's performance is evaluated through on-air contacts, demonstrating effective signal propagation to regions like the Caribbean, South/Central America, the US, and Europe. The article presents measured SWR plots and gain patterns, comparing them against the _NEC_ model predictions to validate the design's efficacy. Practical application notes cover mounting considerations and the benefits of its reversible pattern for targeted DXing on 40 meters, offering a robust solution for operators seeking enhanced directional capabilities without a full-sized rotating Yagi.

The ICOM IC-705, a popular QRP transceiver for portable operations, often presents unique challenges for field deployment. This resource details practical solutions for common portable setup issues, particularly for _Parks on the Air_ (POTA) activations. It describes a custom bracket for connecting antennas to the IC-705 through a backpack's antenna flap, utilizing a BNC female-to-female chassis mount connector to mitigate cable tangles. The author shares experiences with a DIY magnetic loop antenna, noting its ease of tuning with the IC-705 and successful CW contacts on 40 and 20 meters over distances exceeding **1000 miles**. Another modification presented is a strain relief solution for the microphone cord, replacing the standard spring clip with an easier-to-attach method. The page also mentions using a _Wolf River Parks antenna_ for POTA activations and references the QRPGuys DS-1 antenna as another portable option. Firmware updates and integration with an LDG Z11-Pro II auto-tuner are also discussed.