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The resource provides an in-depth analysis of the W6NL 40m _Moxon Yagi_ antenna, utilizing a NEC-2 model to simulate its performance. It details the antenna's design parameters, including element lengths and spacing, and explores critical operational aspects such as feedpoint impedance, SWR across the 40-meter band, and radiation patterns. The document systematically presents the model's setup and the methodology for evaluating the antenna's behavior in different environments, including free space and over real ground. Performance data derived from the NEC-2 model illustrates the antenna's forward gain, front-to-back ratio, and beamwidth. For instance, the model predicts a free-space gain of approximately **6.5 dBi** and a front-to-back ratio exceeding **20 dB** at resonance. Comparisons are drawn between free-space performance and operation at various heights above average ground, demonstrating the impact of ground proximity on take-off angle and overall efficiency. The analysis also touches upon the antenna's bandwidth characteristics, indicating its suitability for the entire 40-meter band with acceptable SWR.

The QRP choke balun described utilizes a high permeability ferrite rod and RG-174 coax, aiming to present high impedance to common-mode currents across the HF spectrum. The construction involves winding as many turns of RG-174 as possible around the ferrite rod, then encapsulating the assembly with hot glue. This design prioritizes maximizing inductance to suppress unwanted shield currents, particularly in unbalanced antenna configurations. While the balun's effectiveness is subjectively reported as good, a potential design consideration involves the dielectric properties of the hot glue. This material could increase turn-to-turn capacitance, potentially reducing the balun's performance at higher HF frequencies, though this specific aspect has not been formally tested by the author, _AA5TB_. The project serves as an illustrative example of a practical, junk-box construction rather than a rigorously engineered solution. Photographs detail the evolution of the balun, from the initial winding process to its integration within a _B&W dipole center insulator_ and final camouflaged assembly.

Designing **Moxon Rectangle** antennas often involves an urge among builders to find simple "magic formulas" for element lengths. L. B. Cebik, W4RNL, argues against this simplistic approach, emphasizing that antenna dimensions do not scale linearly and are influenced by factors like wire size and height above ground. This resource presents a procedure for developing sensible design equations, starting with uniform-diameter elements and perfectly conductive materials, with adjustments for real-world materials like copper and aluminum. The core of the method involves judicious **NEC modeling** (versions 2, 3, or 4) to create a baseline dataset for regression analysis, ensuring models meet specific performance standards for gain, front-to-back ratio, and feedpoint impedance. The derived equations, presented as a BASIC program, allow for calculating Moxon dimensions (A through E) based on wire diameter in wavelengths and design frequency. W4RNL demonstrates the efficacy of these equations by designing and testing Moxon Rectangles for 7.15 MHz (AWG #12 wire), 28.5 MHz (1" tubing), and 146 MHz (0.125" rod). Modeled performance data, including gain, front-to-back ratio, and feedpoint impedance, are provided for both perfect and real-world materials, showing high efficiency and close adherence to design goals. The article also references a standalone Windows program by AC6LA that automates these calculations and generates EZNEC or NEC models.

Operating a ZS6BKW antenna often involves understanding its lineage from the _G5RV_ design, with specific modifications by ZS6BKW to optimize performance on several bands. Through computational analysis and field measurements, the antenna's dimensions were refined to allow operation on 10, 12, 17, 20, and 40 meters without an antenna tuner. For 80, 30, and 15 meters, a tuner is necessary, though efficiency on 30 and 15 meters is noted as not particularly high. The physical configuration consists of two 13.755-meter radiating elements fed by a 12.20-meter section of 450-ohm ladder line. Tuning the antenna on the 20-meter band is critical, and any deviation in the ladder line's characteristic impedance necessitates recalculating the element lengths. The design is also referenced in the 12th edition of _Rothammel's Antennenbuch_, page 219. Proper common mode current suppression is crucial at the transition from ladder line to coaxial cable. This can be achieved with a common mode choke, such as several turns of coax wound into a coil or over a ferrite toroid like an Amidon T130. While a 1:1 balun is an option, it may introduce issues.

The document details the construction of a compact, two-element Quad antenna specifically designed for the 10, 12, and 15-meter HF bands, featuring a single feedline for all three bands. It provides specific dimensions for the driven element and reflector loops, along with boom length and spacing, emphasizing a **0.12 wavelength** spacing between elements. The design incorporates a gamma match for impedance transformation and uses PVC tubing for spreaders, aiming for a lightweight yet robust structure suitable for portable or restricted-space operations. Performance measurements indicate a forward gain of approximately **6 dBd** on 10 meters and a front-to-back ratio of _20 dB_ on 15 meters, demonstrating effective directivity and signal rejection. The antenna exhibits a VSWR below 1.5:1 across the target bands, achieved through careful tuning of the gamma match. This compact Quad offers a viable directional solution for HF DXing and contesting, particularly where full-size Yagis are impractical.

The "REAL TIME ANTENNA GAIN COMPARATOR SYSTEM" by IK0BDO details a low-budget amateur radio tool designed for optimizing homebrew VHF/UHF antennas. It facilitates the simultaneous comparison of two antennas, one a known reference (e.g., a dipole) and the other under test, displaying their relative gain directly in decibels. The system addresses limitations of previous measurement benches by enabling on-field optimization, accounting for balun performance, impedance mismatching, and cable losses. The core of the device is an electronic solid-state switch utilizing PIN diodes, which alternates signal sampling from the two antennas 100 times per second. This rapid switching prevents the receiver's Automatic Gain Control (AGC) from compensating for signal differences, allowing for precise comparative measurements. The document includes detailed schematic diagrams for both the RF switching unit and the associated measure unit, which employs two VU-meters to display cyclic signal levels. It also provides guidance on setting up the PIN diode switching with an oscilloscope and adjusting trimmer potentiometers P1, P2, and P3 for optimal operation. Further sections cover the construction of VHF (144.150 KHz) and UHF (432.360 MHz) beacons for testing, along with critical considerations for selecting an appropriate test range or site. Recommendations include maintaining a minimum distance of 50 wavelengths between transmitting and receiving positions, avoiding ground reflections, and using reference antennas with gains similar to the antenna under examination. The author notes satisfactory results from measurements on dipoles and other antennas, highlighting the system's ability to appreciate fractional decibel differences.

This resource details the conversion of an 80m elevated vertical antenna to include 160m operation, focusing on a relay-switched design over a trap-based approach. It presents specific feedpoint impedance values, such as **32 ohms** for 80m and **14 ohms** for 160m, and discusses the challenges of SWR drift encountered with the prior trap system during RTTY contesting. The article thoroughly explains the design choices for elevated radials, referencing _N6LF QEX data_ to debunk common myths regarding radial length and height, demonstrating that non-resonant radials can offer superior current uniformity. The construction section provides practical insights into building the vertical, including guying strategies, material selection from scrap pipe, and weatherproofing the relay assembly. It highlights the use of a common mode choke for the relay switching line, measuring approximately 5K ohms on both 160m and 80m, and details the L/C matching network's role in achieving a 50-ohm match at the end of a 300-foot RG-11 run. The author describes a precise VNA-based radial trimming procedure, achieving resonant values within a 3 KHz range. The content emphasizes the practical application of theoretical antenna principles, particularly concerning the interaction between the vertical element, cap hats, and the matching network. It offers a candid assessment of component selection, such as using junkbox parts and acknowledging the need for future upgrades to static drain resistors. The article serves as a comprehensive case study for advanced antenna builders tackling multi-band vertical designs.

Presents the mechanical and electrical specifications for a 5-element Yagi beam antenna designed for the 6-meter band. The resource details element lengths, spacing, and boom dimensions, specifically utilizing _EMT conduit_ for construction. It includes a diagram illustrating the element layout, a coaxial balun connection, and a reported SWR curve, providing a practical blueprint for hams to replicate the design. The design achieves a reported SWR of **1.1:1** at 50.125 MHz, indicating efficient impedance matching across the primary 6-meter DX window. The boom length is specified at 2.44 meters (8 feet), with element lengths ranging from 2.87 meters for the reflector to 2.59 meters for the director 3. This configuration suggests a gain figure typical for a 5-element Yagi, likely in the range of **9-10 dBi**, making it suitable for local and sporadic-E DX contacts.

The PDF document, titled "J-Poles," presents various J-pole antenna designs covering the 50 MHz to 450 MHz frequency range. It includes construction details for several specific bands, such as a 6-meter J-pole, a 2-meter J-pole, and a 70-centimeter J-pole. The content outlines the fundamental principles of J-pole operation, including the quarter-wave radiator and half-wave matching stub. Each design features specific dimensions for elements like the radiator length, stub length, and spacing, often expressed in inches. The document also discusses feeding arrangements and impedance matching considerations inherent to J-pole antennas. It provides practical guidance for homebrewing these antennas using common materials like copper pipe or wire elements. The resource offers insights into the advantages of J-poles, such as their omnidirectional pattern and ease of construction, making it a practical reference for radio amateurs interested in VHF/UHF antenna projects.

For radio amateurs seeking compact and efficient antenna solutions, particularly for restricted spaces or noise reduction, HF loop antennas present a viable option. This resource compiles several articles from the ARRL, detailing the theory, design considerations, and practical construction of various loop configurations. Topics include small transmitting loops, receiving loops, and multi-band designs, often emphasizing their performance characteristics such as directivity, bandwidth, and impedance matching. The collected articles provide insights into the comparative performance of different loop geometries, such as circular versus square loops, and discuss the impact of conductor size and tuning methods on efficiency. Practical applications are explored, including their use in portable operations, stealth installations, and urban environments where noise mitigation is critical. The content often includes construction diagrams, parts lists, and performance data derived from modeling or field tests, enabling hams to replicate or adapt the designs for their specific operating conditions.

The **70cm Moxon Beam** project outlines the construction and testing of a compact, directional antenna for the 432 MHz band. G3XBM recounts his early 1980s experience with a 4W FM321 transceiver and a Jaybeam 48-element TV antenna, which provided a baseline for his later UHF antenna experiments. This project focuses on a simpler, yet effective, design for local and regional contacts, emphasizing ease of construction and practical field results over complex theory. The article details the specific dimensions and materials used for the Moxon rectangle, including 6mm diameter aluminum tubing for the elements and a PVC boom. G3XBM notes that the antenna was built for portable use, making it lightweight and easily deployable for field operations. The feedpoint impedance was measured at 50 ohms, ensuring a direct match without the need for an external tuner, which simplifies setup. Performance tests included comparisons against a commercial 5-element Yagi, revealing that the Moxon provided comparable forward gain and an excellent front-to-back ratio, crucial for reducing local QRM. The author's observations confirm the Moxon's reputation as a robust performer for its size, suitable for both fixed and portable 70cm operations.

A GSM1800 Moxon Square antenna project is presented, detailing its construction using three 1.5mm copper wire pieces for the reflector and dipole elements. The design inherently offers a 50-ohm feedpoint impedance, allowing direct connection to 50-ohm coax without complex matching networks like baluns or gamma matches, which are prone to high attenuation at 1.8 GHz if not precisely built. The resource includes a construction plan, expected **SWR plots**, and **radiation patterns** for the GSM 1800 band, specifically covering the 1710-1785 MHz transmit (red zone) and 1805-1880 MHz receive (blue zone) segments. The SWR remains below 2:1 across the entire GSM 1800 band, with the main lobe consistently achieving 5-6 dBi gain. While the radiation pattern shows some changes across the band, these primarily affect the back of the antenna, maintaining consistent forward gain. Practical considerations for high-frequency operation are emphasized, such as minimizing coax length (e.g., under 1 meter for RG-174) and selecting appropriate connectors like N, SMA, or BNC to mitigate significant attenuation. The article also discusses direct connection to the phone's RF PCB for minimal loss and notes observed signal strength variations with antenna orientation despite crossed polarization at cell sites.

A 20-meter vertical _Moxon_ antenna, designed for portable operation, is detailed with specific dimensions for its driven and reflector elements. The project outlines the construction process, including the use of PVC pipe for the frame and #14 AWG insulated wire for the elements. The antenna's compact size and directional characteristics make it suitable for field day operations or limited space environments, offering a gain of approximately 5.5 dBi and a front-to-back ratio of 20 dB. Testing revealed a 1.2:1 SWR at 14.250 MHz, demonstrating good impedance matching across the target frequency range. The _Moxon rectangle_ design provides a clean radiation pattern with minimal side lobes, which is advantageous for reducing QRM from unwanted directions. This build offers a practical solution for hams seeking a lightweight, easily deployable directional antenna for 20 meters without the complexity of a full-sized Yagi.

The ZS6BKW antenna, a popular multiband wire antenna, offers improved band matching compared to the traditional G5RV. This construction guide details the process, beginning with specific dimensions: 13.11 meters (43 feet) for the 450-ohm ladder line and initial dipole arm lengths of approximately 14.8 meters each. It emphasizes the critical role of an _antenna analyzer_ for accurate tuning, particularly for determining the velocity factor of the ladder line and achieving a 1:1 impedance match. The article outlines the materials required, including a 1:1 current balun, 450-ohm window line, wire for the dipole arms, and a 50-ohm non-inductive resistor for testing. It provides a step-by-step procedure for cutting the ladder line to its electrical half-wavelength, explaining how to calculate the velocity factor using measured and free-space frequencies. For instance, a measured 50-ohm impedance at 12.54 MHz with a calculated free-space half-wavelength frequency of 11.44 MHz yields a velocity factor of 0.91. Final adjustments involve hoisting the antenna to its operational height and fine-tuning the dipole arm lengths to achieve optimal SWR, specifically targeting 14.200 MHz. The _ZS6BKW_ design is noted for its performance on 80m, 40m, 20m, 10m, and 6m, though it is not optimized for 15m operation. The author, _VK4MDX_, shares practical tips for durable construction using stainless steel wire and cable clamps.

The resource details the construction of a 6-meter _Moxon_ antenna, presenting two distinct versions: one horizontally polarized for 50-51 MHz CW/SSB and another vertically polarized for 52-54 MHz FM. It specifies the use of 5/8 inch OD and 1/2 inch OD aluminum tubing, with 3/8 inch OD solid aluminum for corners, and provides a comprehensive material cutting schedule. The design aims for robust, portable construction, with all materials costing under $100. Detailed drawings and EZNEC models are referenced for precise dimensions and assembly, ensuring accurate element spacing and impedance matching. The EZNEC model for the H-POL version predicts a gain of **11 dBi** and a front-to-back ratio of **25 dB** at 50.5 MHz, while the V-POL version shows a gain of **6.7 dBi** and a front-to-back ratio of **36 dB** at 53 MHz. The article includes practical SWR measurement advice, noting the impact of coax length and loss on analyzer readings. Field tests during a tropical storm demonstrated the antenna's durability and performance, yielding numerous contacts across significant distances, including California, Colorado, and Texas, on SSB and PSK.

This resource, "Transistor Audio Preamplifier Circuits," offers comprehensive design guidelines for constructing **bipolar transistor** audio preamplifiers. It delves into critical aspects such as quiescent current setting, voltage gain calculation, and the impact of various component choices on circuit performance. The content provides several _schematic diagrams_ illustrating different preamplifier configurations, including single-stage common emitter and two-stage designs, alongside explanations of their operational characteristics and practical implementation considerations. The analysis extends to frequency response, noise performance, and distortion, providing insights into optimizing these parameters for specific audio applications. The resource presents calculated gain figures for various stages, demonstrating how to achieve desired amplification levels. It also discusses the importance of proper power supply decoupling and input/output impedance matching, crucial for integrating these preamplifiers into larger audio systems or ham radio transceivers. The practical application of these designs is evident in their suitability for microphone preamplifiers or general-purpose audio amplification.

Presents the construction of a 10-meter Fractal Quad Yagi (FQY) antenna, detailing the design principles and practical build steps. The article highlights the antenna's compact size, with elements measuring just over 4 feet per side, making it suitable for easy erection and rotation with a TV rotator. It claims an impedance close to 50 ohms, allowing direct feed with 50-ohm coax, and specifies a 3 dBd gain with a front-to-back ratio exceeding 25 dB. Bandwidth is reported at 500 kHz for less than 2:1 VSWR. The resource includes a segment chart (Fig. 1) illustrating the precise lengths for each wire segment of the driven element and reflector, noting adjustments for different wire diameters. Construction utilizes readily available materials such as #9 aluminum ground wire and plastic water pipe for spreaders. The author, _KF7BS_, describes fabricating the framework, bending the fractal elements, and mounting them, including modifications like adding a small stub for reflector tuning. A materials list is provided, detailing items like 40-ft rolls of #9 Radio Shack aluminum ground wire and 1/2-inch plastic water pipe. Scaling equations for the driven element are discussed for different frequencies, such as designing for the CW band. The article references _Chip Cohen NIIRV_'s_ original _Fractenna_ website as the inspiration for the design.

Quad and loop antennas comparisons, evaluating the impedance and gain of both antennas and considerationso n horizontal loop antennas for low bands by PA0FRI

A 2m Moxon antenna project, designed for the 145 MHz amateur radio band, provides a compact, directional solution for VHF communications. This resource details the construction process, specifying materials like PVC pipe for the frame, copper wire for elements, and a SO-239 connector for the feedpoint. The design emphasizes ease of build for hams seeking a gain antenna with good front-to-back ratio for local ragchewing or contesting. The project outlines precise element lengths and spacing, crucial for achieving the desired impedance and radiation pattern. It includes a visual representation of the antenna's dimensions and assembly, allowing for straightforward replication. The Moxon's inherent characteristics offer a practical alternative to larger Yagi arrays, particularly for portable operations or restricted spaces, while still delivering effective directivity and gain.

The **2M Moxon antenna** design presented operates at 144 MHz, providing a compact, directional solution for VHF communications. Construction involves aluminum tubing for the elements, with specific dimensions for the driven element and reflector to achieve optimal performance. The design aims for a good front-to-back ratio and a relatively low SWR across the 2-meter band, making it suitable for portable or fixed station use where directivity is beneficial. Element lengths are critical for proper resonance and pattern. The driven element measures approximately 38.5 inches, while the reflector is slightly longer at 40.5 inches. Spacing between the elements is 12 inches, forming the characteristic Moxon rectangle. This configuration yields a gain of about 5.5 dBi and a front-to-back ratio exceeding 20 dB, which is advantageous for reducing interference from unwanted directions. Feedpoint impedance is close to 50 ohms, allowing direct connection to coaxial cable without complex matching networks. The antenna's lightweight structure, typically under 2 pounds, facilitates easy deployment and rotation, making it a practical choice for field operations or as a compact home station antenna.

Demonstrates the design principles and performance characteristics of **corner reflector antennas**, emphasizing their high gain and directional properties. It covers critical design factors such as the corner angle and the spacing between the radiating dipole and the reflector vertex. The resource explains how reducing the corner angle increases gain but lowers feed impedance, making matching more challenging. Practical angles of 90 degrees or 60 degrees are discussed, with 90 degrees offering easier impedance matching despite slightly lower gain. Details key design considerations, including reflector side length exceeding two wavelengths and reflector width greater than one wavelength for a half-wave radiator. It specifies reflector construction using wire netting, sheet metal, or parallel metal spines spaced less than 0.1 wavelength. The article provides a table with general dimensions for UHF and VHF bands, noting typical impedance values of 50 to 75 ohms and expected SWR of 1.7:1 on the lower band edge. Adjustable radiator-to-vertex spacing is highlighted as crucial for final tuning.

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.

This online guide details the microphone pinout for the Kenwood TR-7950 transceiver, specifically addressing the wiring configuration for a dynamic mobile microphone with a **500 Ohm** impedance. It provides a pin-by-pin breakdown for the 6-pin microphone connector, identifying the function of each active pin. The resource specifies that Pin #1 is for the microphone audio (white wire), Pin #2 controls the _PTT_ (black wire), Pin #3 activates the memory down function (blue wire), and Pin #4 controls the memory up function (red wire). Pin #6 is designated as the ground connection, while Pin #5 remains unused in this configuration. The document focuses on the physical wiring necessary to restore microphone functionality to the Kenwood TR-7950, a transceiver capable of **45 watts** output on the _2m band_. It directly addresses the technical challenge of re-establishing correct electrical connections after microphone wires have been disconnected from the connector. The information facilitates proper microphone operation for simplex QSOs and other voice communications. DXZone Focus: Online Guide | Microphone Pinout | Kenwood TR-7950 | PTT Wiring

The GW3YDX Super Moxon antenna design improves upon the standard Moxon Rectangle by incorporating additional directors in a rectangular configuration, yielding enhanced directivity and gain. For the 6m version, modeling with 4NEC2 and EZNEC+ indicated a 3dB gain increase and a 26.5dB front-to-back ratio, with VSWR below 1.5:1 between 50.0 and 50.3MHz when optimized for 50.1MHz. This design achieves a narrower -3dB power point beamwidth of 60° compared to the original Moxon's 80°, contributing to better QRM rejection. The boom length for the enhanced design is just under 2m, approximately double the original Moxon's, with no increase in wingspan. Construction details include tubing lengths for 6m, 4m, and 2m versions, with specific dimensions provided for elements A through M, measured to tubing centers. For instance, the 6m version uses a 2160mm element A and a 2140mm element H. The design maintains a 50-ohm feed impedance, with practical models showing VSWR plots consistent with simulations after minor adjustments to driven element lengths. The article also references Moxgen software for initial Moxon parameter calculation and NEC/EZNEC model generation. The 2m Super Moxon version measures approximately 30" x 25", demonstrating the compact nature of the design across different VHF bands. The article highlights the antenna's performance in real-world DX contacts on 6m, achieving contacts with over 80 stations in the USA from a modest QTH.

Accurately determining an antenna's feedpoint impedance is crucial for optimal performance, especially when experimenting with new designs or making adjustments. While SWR meters provide basic information, a full complex impedance measurement reveals the resistive and reactive components, which are essential for proper matching. Modern antenna analyzers, like the _Palstar ZM30_ or MFJ259B, simplify this task, but measurements taken through a transmission line require careful interpretation due to impedance transformation. This resource details a calibration method to precisely account for the effects of the feedline. It explains how a transmission line can significantly alter the measured impedance, illustrating this phenomenon with a Smith Chart example where an 80m antenna's [22 + j6] Ohms feedpoint impedance transforms to [82 + j45] Ohms after a 10m line. The guide demonstrates using a transmission line calculator applet, such as the one by W9CF, to reverse this transformation. It outlines the process of calibrating a specific length of RG174 coax, showing how an initial 26ft estimate was refined to **25.85ft** to accurately predict a known 22 Ohm load, significantly improving accuracy over uncalibrated results.

An easy to deploy antenna, commonly considered the best solution for portable operations. Thir article includes a simple LC parallel circuit to match the impedance by IW7EHC

The resource details the construction of a 3-element Yagi antenna specifically designed for the 6-meter band, providing coverage across 50-54 MHz. This antenna design, originally featured in _QST_ August 2007, emphasizes a short boom configuration while maintaining a wideband response. Key specifications include a 50 Ohm SWR of less than 2:1 across the entire band, achieved through specific element lengths and spacing. The design utilizes aluminum tubing for elements and boom, with detailed dimensions provided for the driven element, director, and reflector. Performance characteristics indicate a forward gain of approximately 7.5 dBi and a front-to-back ratio of 18 dB at 50.125 MHz, according to _NEC2_ modeling. The antenna's compact size, with a boom length of 1.83 meters (6 feet), makes it suitable for portable operations or installations with limited space. Construction involves standard amateur radio workshop tools and materials, with a gamma match for impedance transformation to 50 Ohms. The design prioritizes ease of construction and repeatable performance for the 6-meter enthusiast.

Selecting appropriate cabling for amateur radio installations, whether for antenna feedlines, control lines, or station wiring, is critical for optimal performance and safety. This resource provides access to a manufacturer specializing in a broad range of electronic and electrical cables, including options suitable for various ham radio applications. Their product line encompasses standard and custom cable solutions, designed to meet specific operational requirements for both indoor shack setups and outdoor antenna systems. The company emphasizes _proven quality_ and compliance, with products certified by the Canadian Standards Association (CSA), Underwriters Laboratories (UL), and Intertek (ETL). Their quality management system is registered to _ISO 9001:2015_, ensuring consistent product standards. They offer competitive pricing and utilize AI-logistic tools for reliable on-time delivery, serving customers globally with technical support. Access to detailed technical specifications and an online quote tool is available for registered site members, facilitating precise cable selection for projects requiring specific impedance, shielding, or environmental ratings.

Demonstrates the construction of a 144 MHz turnstile antenna, detailing its design for omnidirectional, horizontally polarized VHF operation. The resource outlines the physical dimensions and materials required, including specific lengths for the radiating elements and the use of _RG-58_ coaxial cable for phasing. It covers the assembly process, emphasizing the critical spacing and connection points to achieve the desired radiation pattern and impedance matching for the _2-meter band_. The article presents measured _SWR_ performance across the 144-146 MHz segment, showing a low SWR of 1.2:1 at 144.5 MHz, which is suitable for general VHF use. It compares the turnstile's performance to a 9-element Yagi, noting the turnstile's advantage in providing consistent signal strength from all directions without requiring a rotator. Practical application for local FM simplex and repeater operations is implied, offering a simple yet effective antenna solution for fixed or portable stations.

One point eight MHz to 30 MHz is the operational bandwidth for this 4:1 Ruthroff voltage balun, designed to interface an unbalanced T-Match network with a balanced antenna system. The project details the construction using a _T200-2_ powdered iron toroid core, tightly wrapped in PVC electrical tape for insulation, and wound with 17 double bifilar turns of 1.25mm enamelled copper wire. This outboard balun offers flexibility, allowing hams to trial various baluns based on antenna system and impedance characteristics, rather than integrating it directly into the tuner. The resource includes a schematic of the balun, a wiring diagram showing winding connections, and a table suggesting alternative toroid cores like the T80-2 or T400-2 with corresponding winding counts. Component sourcing is straightforward, listing items such as the _Amidon_ T-200-2 core, SO-239 connector, and a sealed polycarbonate enclosure from Jaycar. Performance evaluation was conducted using an _AIM 4170C_ antenna analyser, demonstrating efficient 1:4 voltage transformation across the specified HF spectrum. Further efficiency tests involved measuring RF power loss at various frequencies, revealing minimal loss—less than 0.7 dB from 3.6 MHz to 30 MHz, and only 2.0 dB at 1.8 MHz. These measurements, performed under ideal 50-ohm conditions, confirm the balun's effectiveness as a low-loss interface for multi-band antenna systems. The page also links to several other balun and unun projects, including 1:1 current and voltage baluns, and 9:1 voltage ununs, providing a broader context for impedance matching solutions.

Presents a QRP AM/CW transmitter project specifically designed for the 10-meter band, utilizing a crystal oscillator and a collector-modulated AM oscillator. The design employs a 2N2219(A) transistor in a Colpitts configuration, generating 100 to 350 mW of RF output power depending on the 9-18 Volt supply voltage and modulation depth. Frequency stability is maintained by a 28 MHz crystal, with fine-tuning possible via a Ct1 trimmer capacitor for approximately 1 kHz adjustment. The resource details the RF oscillator stage, implemented with a 2N2219 NPN transistor, emphasizing frequency stability and low power dissipation. It also covers the amplitude modulation stage, managed by a 2N2905 PNP transistor, which impresses audio information onto the carrier. Selective components (C3, C4, C7, C5) enhance voice frequencies within a +/- 5 kHz bandwidth, and modulation depth is controlled by R2 and R3. The project includes a 3-element L-type narrow bandpass filter (Ct3, L3, C10) to suppress harmonics and ensure a clean output signal. The project provides a complete schematic diagram, a comprehensive parts list including specific capacitor, resistor, and inductor values, and construction notes for the coils (L1, L2, L3). It also offers practical advice on enclosure requirements, suggesting an all-metal case or a PVC box with graphite paint for RF shielding. Operational parameters such as current draw (27mA@9V to 45mA@16V) and input impedance (50 Ohms) are specified, alongside guidance on antenna matching and the importance of a valid amateur radio license for 10-meter band operation.

Operating on the 2200m band (135.7-137.8 kHz) often presents challenges for amateur radio transceivers, which typically exhibit poor receiver performance at these very low frequencies. This project addresses the issue by providing a design for a dedicated 137 kHz antenna preamplifier, specifically tailored to improve signal reception for radios such as the _Yaesu FT-817_. The preamplifier circuit utilizes a low-noise FET input stage, crucial for minimizing self-generated noise and maximizing the signal-to-noise ratio from weak LF signals. The design includes a detailed schematic, component values, and construction notes, enabling homebrewers to build a functional unit. The goal is to achieve significant gain, making the faint signals on 2200m more discernible and improving overall band usability. Key design considerations include impedance matching to typical antenna systems and ensuring stable operation across the narrow LF segment. The circuit aims for a **low noise figure** and sufficient amplification to overcome the inherent limitations of general-purpose HF transceivers when operating below **200 kHz**.

A 6 dB gain Moxon rectangle antenna, designed for the 2-meter band, offers an excellent solution for hams seeking a compact, directional antenna for **SSB** operation, particularly in restricted spaces like an attic. This design emphasizes ease of construction using readily available materials such as 4mm OD brass tubing and plywood, making it an accessible project for many radio amateurs. The antenna's inherent characteristics, including a high front-to-back ratio of 37 dB and a 50-ohm feed impedance, contribute to its effectiveness in mitigating local noise and focusing radiated power. The project leverages the free MoxGen program for precise dimension calculations based on the desired frequency and wire size, and utilizes 4nec2 for pattern analysis, confirming a 3 dB beamwidth of 80 degrees. Construction involves bending brass tubing for the driven and passive elements, mounting them on an 800 x 350 mm plywood boom, and securing them with cable clips and epoxy resin. Initial SWR measurements at 144.3 MHz showed 1.6:1, which improved to 1.3:1 at 145.3 MHz across a flat band from 144.1 MHz to 145.5 MHz after adding a **coaxial choke** to mitigate common mode current.

Demonstrates the construction of a double bazooka antenna, detailing its historical development from MIT radar applications in the 1940s to amateur radio use in the 1950s. It explains the antenna's operation as a 1/2 lambda coaxial section with open-ended stubs, acting as a shortened quarter-wave stub at resonance, presenting high impedance. The resource provides formulas for calculating total length (LT = 140/Freq) and coaxial length (LC = 99/Freq) for RG58 CU, along with specific instructions for cutting and soldering components, including a central insulator and end wires. Compares the double bazooka to a standard dipole, highlighting its 98% efficiency and twice the bandwidth. It claims a +3.6dB gain over a dipole (dipole gain 2.15dB) and a 6dB reduction in reception noise due to its closed design, which also minimizes harmonics and TVI. The antenna handles over 1.5kW (2kW PEP) without performance degradation and is effective for DX with a low radiation angle, especially when configured as an inverted V between 90° and 120° with ends 2 meters above ground. It eliminates the need for a balun and can be fed directly with 50-ohm coaxial cable.

A fractional bandwidth of up to 30:1 characterizes spiral antennas, making them highly effective across a very wide frequency range, often from 1 GHz to 30 GHz. The resource details two primary types: the **Log-Periodic Spiral Antenna** and the **Archimedean Spiral Antenna**, defining each with specific polar functions and illustrating their planar configurations. It explains that spiral antennas are typically circularly polarized, with a Half-Power Beamwidth (HPBW) of approximately 70-90 degrees, and a peak radiation direction perpendicular to the spiral plane. The content elaborates on critical design parameters affecting radiation, including the total length (outer radius) for lowest frequency, the flare rate ('a' constant) for optimal radiation versus capacitive behavior, the feed structure (often an infinite balun) for high-frequency operation, and the number of turns (typically 1.5 to 3 turns). It also discusses the theoretical impedance of 188 Ohms for Log-Periodic spirals, derived from Babinet's Principle, noting actual impedances are often 100-150 Ohms. The article presents a simple construction method for an Archimedean spiral, demonstrating VSWR and efficiency measurements. Measurements from a constructed spiral antenna show a VSWR that is fairly constant across the band, albeit with a mismatch loss of about 3 dB. The antenna efficiency remains around -5 dB (31.6%) across its operating range, indicating a decent wideband radiator despite opportunities for optimization.

The X80 multi-band HF vertical antenna, a commercial iteration of the Rybakov design, exhibits a physical length of 5.5 meters, or approximately 18 feet, and is constructed from aluminum tubing. It operates as a non-resonant vertical, requiring an external antenna tuner for impedance matching across its intended operating frequencies. The antenna's design incorporates a 1:4 UNUN at its base, facilitating a nominal 50-ohm feed point impedance for the coaxial cable. Performance observations indicate effective operation on 40 meters, 20 meters, 15 meters, and 10 meters, with reduced efficiency on 80 meters and 160 meters due to its relatively short electrical length for these lower bands. Comparative analysis with a G5RV dipole and a half-wave end-fed antenna reveals the X80 offers a lower take-off angle, beneficial for DX contacts, particularly on the higher HF bands. Field tests conducted with an Icom IC-706MKIIG transceiver and an LDG AT-100ProII autotuner demonstrate the X80's ability to achieve acceptable SWR across 80m through 10m. The antenna's compact footprint and ease of deployment make it suitable for restricted spaces or portable operations, though its performance on 80 meters is noted as a compromise compared to full-size resonant antennas.

Protecting amateur radio equipment from transient overvoltages requires robust lightning and surge protection, which is the focus of Electronic Specialty Products. The company provides various devices, including coaxial lightning arrestors for antenna feedlines and surge protectors for AC power lines and data circuits. These devices are engineered to divert high-energy surges, such as those caused by direct or indirect lightning strikes, away from sensitive transceivers, amplifiers, and computer components, thereby preventing catastrophic damage. Key products include the _Coaxial Lightning Protector_ series, designed for various impedance levels and frequency ranges up to 3 GHz, and the _AC Line Surge Protector_ for shack power distribution. Effective deployment of these protection devices can significantly reduce the risk of equipment failure and ensure operational continuity during severe weather. For instance, a properly installed coaxial arrestor can handle peak currents of **20 kA**, while AC line protectors offer clamping voltages typically below 400V. Comparing different models reveals varying levels of insertion loss and return loss, with some coaxial units exhibiting less than 0.1 dB loss at 500 MHz, making them suitable for high-performance HF and VHF/UHF operations. Integrating these components into a comprehensive grounding system is crucial for achieving maximum protection against both common-mode and differential-mode surges.

This web article by VK3BLG details the construction of an experimental 70cm (432 MHz) circularly polarized patch antenna, intended for satellite communication. The resource provides dimensions, feed point specifications, and impedance matching considerations for a single patch element, with discussion extending to array configurations for circular polarization. Construction involves a copper patch element on a dielectric substrate, fed via a coaxial cable. The design is based on information derived from AO-40 satellite antenna specifications, focusing on achieving circular polarization for satellite reception. The article includes specific dimensions for the patch and feed points, along with impedance values. Validation is implied through on-air satellite reception reports, with initial signal reports of **1 S-point above noise** for AO-40 beacons using a grid reflector, improving to **3-4 S-points above noise** with a 2-turn helical feed. The author references a _NanoVNA_ for impedance measurements and discusses the relationship between slot and dipole antennas in the context of patch design. DXZone Focus: Web Article | 70cm Patch Antenna | On-Air Satellite Reception | Circular Polarization

Designing and constructing portable wire antennas for HF operations, this resource explores several configurations including the _foldback dipole_ for space-constrained setups and an inductively shortened dual-band dipole for 20m and 40m. It details the calculation of inductance for shortened elements, providing a Visual Basic 6.0 program screenshot that illustrates determining coil parameters like turns and length for a **25.5 uH** inductor. The document emphasizes practical considerations such as adjusting wire lengths for optimal SWR, noting that a dual-band dipole achieved SWR below 2:1 on both 20m and 40m, with careful adjustment bringing it under 1.5:1. Further, the resource describes a half-wave antenna matched with a coaxial stub, a method often referred to as the _Fuchskreis_ in German amateur radio circles, to transform the high feedpoint impedance to 50 Ohms. This monoband solution, for a 20m application, uses a stub length of **2.98m** (0.216 lambda multiplied by coax velocity factor) and a shorted stub of approximately 48cm. The coaxial stub design is highlighted for its resilience to ground proximity, allowing it to be rolled up or laid on the ground with minimal SWR impact, making it highly suitable for portable QRP operations.

With the view to establish a quick and easy multi-band antenna deployment for portable and camping operations a simple long wire antenna with an earth or earth plus counterpoise arrangement with a 9:1 voltage unun including a tuner or simply with a tuner is one possible solution. With the 9:1 voltage unun and wire lengths suggested in the below tables the antenna should present non extreme impedances for all HF amateur band frequencies. This page is far from complete and represents the ongoing investigation into this type of antenna. Experiments to date seem to have raised more questions than obvious answers.

Presents construction details for Moxon antennas, specifically focusing on 10-meter and 17-meter band configurations. It covers practical aspects of building these directional wire arrays, including element spacing, feedpoint considerations, and material choices for optimal performance. The resource emphasizes homebrewing techniques suitable for amateur radio operators. Discusses the advantages of the Moxon rectangle design, such as its compact footprint compared to a full-size Yagi and its favorable front-to-back ratio. It provides insights into achieving proper impedance matching and structural integrity for portable or fixed installations. The content includes photographic examples of constructed antennas. Explains the iterative process of tuning and optimizing Moxon antennas for specific frequency segments within the 10m and 17m bands. It offers guidance on minimizing SWR and maximizing gain, drawing from real-world building experiences to assist constructors in replicating successful designs.

Hi-Z Antennas offers specialized high-impedance receiving systems, primarily focusing on phased vertical arrays for HF reception. Their product line includes preamplifiers designed for shortened vertical antennas, featuring optimized 15dB gain and array-matched characteristics. These components are engineered to enhance weak signal reception and improve signal-to-noise ratio across the HF spectrum. The company provides controllers for managing multiple vertical elements in a phased array configuration, enabling directional reception patterns. These systems are particularly effective for mitigating local noise and interference, a common challenge in urban and suburban operating environments. Specific offerings include solutions for 160-meter and 80-meter bands, addressing the unique requirements of low-band DXing. Technical details often reference components like the 2N3866 transistor in preamp designs and discuss concepts such as out-of-band attenuation. The focus remains on optimizing receiving antenna performance through impedance matching and active amplification, rather than transmit capabilities.

G/T (Gain-to-Noise Temperature) is a critical figure of merit for evaluating the receive performance of VHF/UHF antennas, particularly for weak-signal work like EME (Earth-Moon-Earth) or meteor scatter. This resource presents extensive simulation data for numerous 2-meter and 6-meter Yagi antenna designs, originally compiled by _VE7BQH_ (Lance Johnson). The lists, updated as of October 2017, include various antenna models from designers such as _DK7ZB_, G0KSC, and K1FO, providing key performance parameters. Each entry details the antenna's G/T value, gain, front-to-back ratio, beamwidth, and VSWR at specific frequencies like 144.1 MHz or 145.0 MHz. The data facilitates comparison of different Yagi configurations, including those with folded dipoles and varying intrinsic impedances, aiding radio amateurs in selecting optimal antennas for their specific operational needs on the 2-meter and 6-meter bands.

The **136kHz Vertical Antenna** at G3YMC employs a Butternut HF2V structure, standing 10m tall. It integrates a 6.5mH loading coil to achieve resonance, with a matching transformer for impedance adjustment. The antenna's configuration includes top loading via a 12m horizontal wire, enhancing capacitive impedance. Initial measurements indicated a high impedance of around 300 ohms, necessitating a transformer for a 50-ohm match. Despite challenges with ground losses, the vertical antenna has shown improved performance in specific directions, filling nulls present in the previous loop antenna setup. The tuning remains broad, with variations due to environmental factors affecting the matching. Ongoing adjustments and comparisons with the loop antenna will continue to refine its effectiveness.

Presents the construction of a 2-meter **Skeleton Slot Yagi** stack, detailing the design process and practical considerations for VHF operation. The author shares insights from building and testing this antenna, emphasizing its performance characteristics for local and extended range contacts. The project outlines the specific dimensions and materials used, providing a clear path for other radio amateurs to replicate or adapt the design for their own stations. The resource covers the unique aspects of the Skeleton Slot radiator, explaining how its geometry contributes to gain and pattern control. It includes discussions on impedance matching and feedline considerations crucial for optimizing power transfer and minimizing SWR. The article draws on real-world testing, offering practical results that validate the theoretical design. This project serves as a valuable reference for those interested in custom VHF antenna solutions.

The NB6Zep Antenna, an electrically shortened 80-meter end-fed wire, addresses space constraints for low-band operation by integrating two loading coils into a 37-foot wire. This design, modeled with _EZNEC_, explores configurations like the quarter-wave sloper and inverted-L, with the latter providing a more vertical radiation pattern and practical backyard deployment. The resource details specific coil construction, recommending 21 uH coils made from _BW coil stock #3026_ or similar, and outlines wire segment lengths for optimal tuning. Performance analysis indicates a radiating efficiency of approximately 27% with good ground conductivity, resulting in a signal typically 3-4 dB down compared to a full-size quarter-wave vertical. The antenna exhibits a narrow bandwidth, around 50 kHz, due to its high Q, necessitating a tuner for broader band operation. Feedpoint impedance is low, with ground resistance playing a critical role in achieving a usable SWR. The article emphasizes the importance of an effective ground rod at the feedpoint for proper operation and tuning, suggesting an antenna analyzer for precise adjustments. It confirms the antenna's suitability for DX, citing successful contacts from Oregon to the East Coast and Hawaii on a 160-meter variant, making it a viable option for urban operators seeking low-angle radiation on 80 meters.

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.

Demonstrates the principles of effective HF multi-band antenna systems, emphasizing the use of non-resonant antennas, understanding line attenuation, and the proper application of transmatches and baluns. The resource challenges prevalent amateur radio myths, such as the necessity of a 1:1 SWR at the antenna feedpoint and the misconception that reflected power is lost or damages equipment. It cites authorities like Jim Fisk (Ham Radio Magazine) and M. Walter Maxwell (W2U, QST's "Another Look At Reflections" series) to support its arguments, providing historical context and technical explanations for these long-held beliefs. The article details how to combine non-resonant antennas with appropriate feedlines and matching devices to achieve broad-band operation. It compares coaxial cable losses with those of balanced open-wire lines, illustrating how ladder line can significantly reduce attenuation and handle higher impedances, enabling an 80-meter dipole to operate effectively across multiple HF bands. Practical guidance is offered on transmatch operation, explaining impedance matching principles and debunking the idea that tuners merely "fool" the transmitter. It also clarifies the function and potential misapplication of baluns, particularly transformer-type baluns, in the presence of high SWR.

Presents a construction project for a 1:1 current balun, specifically detailing the _Sorbie Balun and Bottle Choke_ design. The resource outlines the winding technique, employing 4+4 turns of mini coaxial cable on a large ferrite core, and provides insights into the physical assembly. It includes specific material recommendations, such as the type of ferrite and coaxial cable, crucial for achieving the desired impedance transformation and common-mode current suppression. The content covers the practical steps involved in building the balun, from preparing the coaxial cable to securing the windings on the ferrite toroid. It also discusses the integration of the balun into an antenna system, emphasizing its role in maintaining pattern integrity and reducing RF interference in the shack. The resource offers a clear, step-by-step approach, making the project accessible for homebrewers. Illustrations and photographs accompany the text, visually guiding the builder through each stage of construction. The article concludes with performance expectations and considerations for deployment, ensuring the constructed balun functions effectively across the intended frequency range.

A presentation of the Yagi Antennas, and other interesting tid-bits by Brian Mileshosky. The document provides an in-depth exploration of the Yagi-Uda antenna, detailing its historical development, design principles, and performance characteristics. Originally described in the 1920s, the Yagi antenna features a driven element and parasitic elements, including reflectors and directors, which collectively determine its behavior. The document highlights how element lengths, diameters, and spacing influence gain, impedance, and directivity. It also discusses the antenna's reciprocal nature and presents data on typical gain values for various element configurations. Additionally, the text covers practical considerations, such as the construction of a "Tape Measure Yagi" for amateur use, and touches on related antenna types like dipoles and their application in Near Vertical Incident Skywave (NVIS) communication.