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A 9 dB gain 70cm collinear antenna construction is detailed, utilizing eight half-wavelength sections of _RG58/U_ coaxial cable. The design incorporates specific calculations for velocity factor (0.66 for RG58/U) to determine precise element lengths, such as 223mm for a half-wavelength at 444 MHz. A quarter-wave radiating element of #16 solid wire, 169mm long, is added to the top, and a 160mm aluminum tube acts as a quarter-wave counterpoise at the feed point. RF choke baluns, constructed from three _FT50-43_ toroids, are positioned a half-wavelength from the feed point to mitigate common mode current. Assembly involves soldering the coax sections in series, followed by SWR testing during construction and final mounting within a ¾-inch PVC pipe. The article suggests using four half-wave elements for a shorter antenna, noting a potential slight increase in SWR, which can be mitigated with quarter-wave ground radials. The design principles and formulas are scalable for other VHF/UHF bands like 6m, 2m, or 1¼m, providing a versatile homebrew solution for enhanced gain.

This article describes how to make a quadrifilar helix (QFH) antenna easily, from inexpensive materials: uPVC plumbing pipe and RG-58U co-axial cable. A low-cost, easy-to-build Quadrifilar Helix (QFH) antenna for weather satellite reception using uPVC plumbing pipe and RG-58U coaxial cable. Unlike traditional designs requiring copper pipe and plumbing skills, this approach enables construction with basic tools and minimal technical expertise. The antenna's shorter, wider proportions favor higher elevation angles, reducing interference from horizon-level pager transmitters. Electrical connections are simplified at the antenna's apex, with the coaxial cable forming the radiating elements. Testing demonstrated consistent signal strength throughout satellite passes, proving effective weather satellite reception is achievable without precision engineering to sub-millimeter tolerances.

Constructing a **reduced-size coaxial Moxon rectangle** antenna for the 17-meter band is detailed, presenting a method to achieve a compact directional antenna. The resource outlines the use of RG-58/U coaxial cable for elements, enabling a substantial reduction in physical dimensions compared to traditional wire or tubing Moxon designs. It provides specific instructions for tuning coaxial elements using an **MFJ-259B antenna analyzer**, including a formula to calculate trimming lengths based on measured resonance and desired frequency. The article explains how to prepare the coaxial cable for both driven and reflector elements, specifying connections for testing and final assembly. Performance data from an MFJ-259B shows SWR readings between 1.0 and 1.2 across 18.068 MHz to 18.168 MHz, with R values from 51 to 59 ohms and X values of 0 or 6 ohms. The antenna's power handling is approximately 500 watts continuous, limited by the RG-58/U coax. Comparative receive testing against an All-Band Sterba Curtain at 50 feet indicated a 2 S-unit reduction for the coaxial Moxon at 9 feet, suggesting optimal performance at a height of 34-40 feet for a 15-18 degree take-off angle. The design achieves an electrical quarter wavelength with over 30 percent size reduction.

A 70 MHz Moxon rectangle antenna, built with 0.83mm enamelled copper wire and a lightweight fiberglass kite spar frame, offers a compact two-element beam solution for the 4-meter band. This design, originally for HF, scales effectively to VHF, reducing the antenna's width to approximately 75% of a half-wavelength while allowing direct coaxial cable feeding. The author, G6GVI, details the construction process, including the use of an automated design tool for precise dimensions. Initial field testing revealed a VSWR of approximately 1.3, with distinct nulls observed at 90 degrees when the antenna was mounted horizontally. The lightweight build, supported by a wooden block and U-bolt for mast attachment, makes it suitable for thinner mast sections. Further experimentation included testing with vertical polarization and considering its potential for indoor loft installation due to its relatively short major axis, offering a discreet option for urban hams.

A 20-meter Moxon antenna design provides a compact directional solution for the 14 MHz band, achieving approximately **5.5 dBi** of forward gain and a front-to-back ratio exceeding 20 dB. This rectangular wire array, consisting of a driven element and a reflector, offers a smaller footprint than a traditional 2-element Yagi, making it suitable for space-constrained installations. Construction details focus on specific dimensions for the wire elements, fed with 50-ohm coaxial cable. The _Moxon rectangle_ inherently delivers wide bandwidth and a clean radiation pattern, simplifying tuning with a relatively low SWR across the entire 20-meter band. Its robust performance makes it a practical choice for both fixed stations with limited tower space and portable _DXing_ operations. The design's characteristics are particularly beneficial for contesting and long-haul communications on 20 meters.

The document provides a comprehensive overview of baluns, which are devices used to connect balanced loads, like dipole antennas, to unbalanced inputs, such as coaxial cables. It covers various types of baluns, including voltage and current baluns, and their design, construction, and testing. The text discusses the importance of baluns in preventing RF currents on coax shields and their applications in Ham radio setups. It also includes practical advice on selecting and using baluns based on antenna impedance and power ratings, along with detailed performance evaluations and construction tips for different balun configurations.

The cable testing approaches discussed in this article gives an idea about the electrical characteristics of a coaxial cable. Velocity of Propagation, Characteristics Impedance, Return Loss Measurement and more

Delta Electronics Manufacturing, a global manufacturer, specializes in _RF connectors_, adapters, and cable assemblies, providing custom interconnect solutions with superior performance. Their Advanced Vertically Integrated (AVI) global facilities emphasize efficiency, quality, flexibility, and cost control across their product lines. The company serves diverse industries, including broadcast and audio, test and measurement, military, aerospace, and public safety communications. For instance, Delta supplies RF interfaces for military aircraft, satellite launch vehicles, and missiles, maintaining a long-standing QPL supplier status. Their field-tested RF interconnects are also crucial for two-way radios, base station equipment, and antenna systems in public safety applications, ensuring reliable performance in critical communication infrastructure. Delta's solutions extend to commercial aircraft and semiconductor manufacturing, where their RF interconnects power etch equipment, deposition equipment, and chip testing systems worldwide.

Demonstrates MegaPhase's extensive product line of RF and microwave coaxial cable assemblies and components, engineered for demanding applications up to 110 GHz. Key offerings include _Test & Measurement Cables_ with superior phase and amplitude stability, _RF & Microwave Cables_ utilizing _GrooveTube®_ technology for high power systems, and a range of RF components like directional couplers and power dividers. The site details specific cable types such as _Alumibend™_ for space-qualified, ultra-light applications through 90 GHz, and armored cables designed for rigorous environments up to 50 GHz, emphasizing their robust mechanical strength and measurement repeatability. The resource highlights applications across diverse sectors, including space programs like the _Hayabusa_ mission, global security (C5ISR), military airborne systems (MIL-T-81490), telecom, and automated testing. It also provides technical insights through "How To" guides on measuring amplitude/phase stability vs. flexure and proper connector cleaning. The company's commitment to quality is underscored by its rigorous testing protocols and a strong warranty, ensuring reliable operation in critical systems.

Messi & Paoloni offers a range of RF coaxial cables, including the _Ultraflex_ series, specifically engineered for amateur radio applications. These cables feature advanced dielectric materials and high-density braiding, resulting in significantly reduced attenuation across HF, VHF, and UHF bands. For instance, the Ultraflex 7 exhibits a loss of only **2.5 dB per 100 feet** at 144 MHz, making it suitable for demanding DX and contesting operations. The company's product line also includes specialized connectors, such as N-type and PL-259, designed to maintain optimal impedance matching and minimize signal reflections. Each connector is precision-machined to ensure a secure, weather-resistant termination, crucial for outdoor antenna installations and long-term reliability. Messi & Paoloni emphasizes rigorous quality control, with all cables undergoing testing to ensure consistent performance and durability, supporting effective two-way radio communication.

EA4EOZ details the construction and testing of 50 MHz traps, a critical component for multiband antenna designs. The project addresses the challenge of sourcing high-voltage capacitors suitable for trap applications, exploring alternatives to expensive doorknob capacitors. The author successfully fabricated a capacitor using 1.6mm double-sided FR-4 PCB material, achieving a capacitance density of **2.6 pF/cm2**. Utilizing the _VE6YP calculator_, specific L and C values of 30 pF and 0.31 uH were determined for a 2cm diameter coil. Both the FR-4 PCB trap and a coaxial cable trap, constructed from _RG-58_, were built and tuned to approximately 50 MHz using a spectrum analyzer. The coaxial cable trap demonstrated superior performance, exhibiting a notch nearly **20dB deeper** than the FR-4 version. This practical comparison provides insights into trap construction for experimental antennas, with the coaxial cable trap selected for an antenna project intended for operation at up to 100 watts.

Demonstrates the construction of an **ATU-100 (N7DDC)** automatic antenna tuner, detailing the assembly process from component arrival to final enclosure. The resource covers winding the tandem match transformer, connecting the OLED display, and integrating optional control buttons. Specific attention is given to modifying the EEPROM settings for **QRP operation**, reducing the minimum tuning power to 1 Watt, and addressing potential RF interference with CPU by adding capacitors to button connections. The build log includes practical tips such as adapting RG58 coaxial cable strands for PCB mounting and utilizing a repurposed Macbook Pro cover for the custom enclosure. The author references external GitHub pages for comprehensive information, R0AEK's resources for additional details, and a video by MW0SAW for EEPROM configuration across different ATU-100 variants. Future plans involve field testing the completed tuner during SOTA or other portable activations.

The resource details the construction of a J-pole vertical antenna specifically engineered for motorcycle mounting, addressing the common issue of interference with top cases. It outlines the fabrication process, beginning with an aluminum angle bracket for secure attachment to the lateral support, followed by the creation of the antenna's base from an 8mm threaded rod bent into a U-shape, approximately **40mm** wide. The article specifies the precise method for coaxial cable connections using eyelets and 3mm screws, ensuring robust contact. Further construction steps involve fitting a 10mm aluminum tube onto the threaded rod, with a screw securing the radiating element and establishing core contact. The design prioritizes mechanical stability against vehicle vibrations over fine-tuning SWR with sliding collars. Initial testing yielded a _SWR_ of **1.2** across a significant portion of the band, with improvements noted by optimizing the coaxial braid contact point near the support bracket. The document provides practical insights into material selection and assembly, emphasizing durability for mobile operation. It concludes with aesthetic options, allowing the builder to paint the antenna or retain its natural aluminum finish, making it a functional and adaptable solution for UHF motorcycle communications.

VE2AZX's 2013 Radio Talk presentation details the technical aspects of baluns, including reasons for their use, various types, and methods for performance verification using an SWR analyzer. The document specifically examines 1:1 voltage baluns and 4:1 voltage baluns, outlining their winding configurations and typical impedance transformations. It presents empirical SWR measurements for W2AU 1:1 baluns and Unadilla 4:1 baluns, tested with both 50-ohm and 200-ohm resistive loads across the HF spectrum. The presentation further explores the measurement of ferrite impedance and their application in mitigating common-mode currents on feeders and household conductors. Key concepts addressed include balanced-to-unbalanced transformation, ensuring feeder independence from the antenna, and reducing unwanted feeder radiation. The content emphasizes practical testing procedures to ensure optimal antenna system performance and minimize RF interference. Discussions also cover open-circuit tests with SWR analyzers and VNAs to assess winding inductance, distributed capacitance, and insulation quality. The presentation differentiates between voltage and current baluns, explaining how current baluns, particularly those utilizing ferrite cores, reduce outer shield currents without affecting internal coaxial cable currents, thereby preserving the antenna's intended radiation pattern.

A common mode choke/balun, essential for mitigating common mode current on antenna feedlines, is detailed in this construction and measurement guide. It utilizes eight Fair-Rite #2643167851 Mix 43 ferrites housed within a Hammond 1598JSGYPBK plastic case, with RG-8X coax cable forming the windings. The document references design principles from Ian White, GM3SEK's article on cost-effective ferrite chokes. Specific construction details include the layout of three coils to minimize inter-coil coupling and methods for securing the ferrites with foam tape. The resource presents comprehensive measured data, including isolation impedance (magnitude, real, and imaginary components), Q factor, inductance, and phase angle across various frequencies. It also covers the choke/balun's coax frequency response and return loss characteristics. Techniques for measuring choking impedance are thoroughly explained, focusing on S21 transmission measurements with a Vector Network Analyzer (VNA) and testing ferrite beads in both S11 and S21 modes. The guide describes a practical setup using an aluminum sheet or baking foil for measurements and outlines the calculation of series impedance from attenuation in a 50-ohm system. Additionally, it details a method for determining the balun's equivalent L and C around resonance by adding a parallel capacitor.