Search results

The Super J Pole antenna is a co-linear vertical consisting of a number of half wave length vertical elements separated with half-wave length stubs (Tuning stub) feed with a folded matching stub by vk6ysf

Article about omega and gamma matching, related to bandwidth, loss and component failures, heating and power ratings

160m T Antenna broadcast design by Guglielmo Marconi has been built and is used by Jim NN4AA on 160m. Article by G7LRR

Notes on homebrewing antennas by Chris G4CYA, from gamma matching, to phasing antennas, splitters and combiners, baluns and measuring techniques.

21 mhz half wave ant -very low radiation angle - full size and light weight- all coax matching system - decoupling care to prevent low angle radiation degrade

There are lots of good designs for matching transformers for receiving antennas. Make it yourself it's cheap and easy, and very high performance. This is the design used in the TRX-9 transformers.

The 10-meter EH Antenna document details the construction and performance of a specific EH antenna design for the 10-meter band. It describes the integration of an L+L balanced matching network, a key component for impedance transformation, and highlights the addition of a tuned coaxial trap. This trap, consisting of 8 turns of RG58 coax wound around PVC tube and resonated at 29 MHz with a 10 pF capacitor, effectively inhibits common-mode current on the feeder, stabilizing antenna tuning. The resource presents a circuit diagram in Figure 1 and assembly details in Figure 2, illustrating the use of PVC plumbing tube as host material for dipole cylinders made from recycled aluminum tubing. It also explains the fabrication of capacitor stators and slider sections from thin aluminum tubing. The author, Lloyd Butler VK5BR, discusses initial challenges with feeder interaction and how the tuned trap resolved these issues, leading to stable tuning. Limited backyard tests indicate that the antenna, with the trap fitted close to the input connector, might exhibit similar field strength for both low and high angle transmission, suggesting a potential skewing of the signal. The document references previous articles by VK5BR in "Amateur Radio" for further operational details of the matching network and trap functionality.

Constructing a compact, two-band magnetic loop antenna for HF operation, especially from constrained locations like a balcony, presents unique challenges. OK1FOU's design, inspired by DJ3RW's 50 MHz loop, addresses these by employing an unusual side-fed configuration and placing the symmetric, two-section variable tuning capacitor at the bottom of the loop, directly connected to the coax shield. The article provides specific material recommendations, including two 1-meter wooden pales and about 3 meters of thick loudspeaker cable, noting the high current (60A at 100W) in the loop. Construction steps detail forming two turns with a 5 cm gap, using a GDO to pre-tune the open loop to a frequency slightly above the desired highest band, and then integrating the tuning and coupling capacitors. For 10/14 MHz, an open loop resonance of 16-17 MHz is suggested. Practical experience with the 10 MHz band from a third-floor balcony in Prague (JO70GC) shows a 1:1 SWR across most of the band without an external ATU. While DX traffic was modest due to the urban environment, QSO examples with RA6WF, LA6GIA, G0NXA, and LZ1QK on 10 MHz are provided, demonstrating its operational capability.

Constructing a Lindenblad antenna for 137MHz NOAA satellite reception involves specific design considerations for optimal performance. The resource details the use of 4mm galvanised steel fencing wire, 300-ohm television ribbon cable, and wood/plastic components for the antenna structure. Key dimensions for a 137.58MHz-resonant antenna are provided, derived from the ARRL Satellite Handbook, specifying s, l, w, and d as 42, 926, 893, and 654mm respectively. The antenna is designed for Right Hand Circularly Polarised (RHCP) signals, requiring the four folded dipole elements to be tilted clockwise by 30 degrees. A significant aspect covered is impedance matching between the antenna's 75-ohm impedance and a typical 50-ohm receiver input. A twelfth-wave matching transformer, constructed from 117mm sections of 50-ohm RG-58 and 75-ohm RG-59 coax with a 0.66 velocity factor, is described. The article also addresses coaxial cable and connector selection, recommending 75-ohm Type-N connectors for RG-6 cable in professional setups and F56/F59 connectors for general use, while strongly advising against PL-259/SO-259 connectors for VHF. Strategies for mitigating Radio Frequency Interference (RFI) are discussed, including antenna placement to shield from local TV transmitters and the use of commercial or DIY band-pass filters, such as cavity resonators or helical notch filters, along with ferrite chokes on coaxial cables. Antenna orientation is explored, noting the Lindenblad's 'cone of silence' directly overhead and its maximized sensitivity towards the horizon. An experimental vertical tilt of 90 degrees is presented as a method to improve overhead reception and reduce interference from strong horizontal signals, particularly relevant in high RFI environments like the Siding Spring Observatory site.

Demonstrates a practical modification to convert a standard G5RV antenna into a _160-RV_ for effective operation on the 160-meter band. This project addresses the challenge of achieving Top Band resonance with a common multi-band wire antenna, providing a solution for hams with limited space or resources for dedicated 160m antennas. The design utilizes a specific length of 450-ohm ladder line and a 1:1 current balun, acting as a matching section to bring the G5RV's impedance into a usable range for 1.8 MHz. The document includes a parts list, detailed construction steps, and tuning instructions, emphasizing the importance of precise measurements for the ladder line and coaxial cable sections. It also outlines the expected SWR characteristics and power handling capabilities, making it suitable for QRO operation up to 1.5 kW. The _AD1B_ design offers a straightforward approach for extending the utility of an existing G5RV.

This resource details the computer-optimized design of the _ZS6BKW_ multiband dipole, an evolution of the classic _G5RV_ antenna. It begins by referencing the original 1958 RSGB Bulletin article by Louis Varney G5RV, explaining the operational principles of the G5RV's flat-top and open-wire feedline on 20m and 40m, noting its impedance transformation characteristics for valve amplifiers of that era. The article then transitions to the rationale for optimizing the design for contemporary solid-state transceivers requiring a 50 Ohm match. The core of the project involves using computer modeling to determine optimal lengths for the flat-top and matching section, aiming for a VSWR of less than 2:1 on multiple HF bands. It discusses the process of calculating feedpoint impedance based on antenna length and frequency, referencing professional literature from Professor R.W.P. King at Harvard University. The analysis also considers the characteristic impedance (Z(O)) of the open-wire line, identifying a broad peak of adequate values between 275 and 400 Ohms. Specific design parameters for the improved ZS6BKW are presented, including a shorter flat-top and a longer matching section compared to the original G5RV, with a velocity factor of 0.85 for the 300 Ohm tape. The article confirms acceptable matches on 7, 14, 18, 24, and 28 MHz bands when erected horizontally at 13m, and also discusses performance in an inverted-V configuration, noting frequency shifts. The author, Brian Austin ZS6BKW, emphasizes the antenna's suitability for modern 50 Ohm coaxial cable without a balun.

A 7 MHz vertical half-Moxon array, designed by F6IRF, is presented with its MMANA model, featuring a 20cm gap between the two horizontal elements. The design aims for a low take-off angle, crucial for DX work, and includes specific dimensions for the driven element and reflector, which are constructed from 2mm copper wire. The antenna's feedpoint impedance is approximately 50 ohms, allowing for direct coax feed without a matching network, and it is intended for portable or temporary installations. Field results indicate the antenna provides a **3 dB** gain over a quarter-wave vertical, with a front-to-back ratio of **10 dB** on 40 meters. The author notes successful DX contacts into _VK_ and _ZL_ from France, demonstrating its effectiveness for long-haul communication. The design emphasizes simplicity and portability, making it suitable for operators seeking a directional antenna solution for the 40m band without complex setup requirements.

Illustrates the specific wiring and configuration steps required to interface an SGC-230 Smartuner with an Icom IC-706 HF/VHF/UHF transceiver. The document details the necessary connections for power, control, and RF signal paths between the two devices, ensuring proper impedance matching and automatic antenna tuning functionality. It specifies the pin assignments for the IC-706's ACC socket and the SGC-230's control port, crucial for successful integration. Outlines the operational considerations for the combined system, including initial setup procedures and potential troubleshooting tips for common connectivity issues. The resource presents a clear, diagrammatic representation of the interconnections, which aids in visual comprehension of the required cable fabrication or modification. Covers the specific settings within the IC-706 menu that need adjustment to enable external tuner control, such as the 'TUNER' function and other relevant parameters. This ensures the transceiver correctly communicates with the SGC-230 for efficient antenna tuning across various amateur bands.

The K0RWU 75-meter mobile antenna design features a 7.5-foot overall length, incorporating a 2.5-foot loading coil wound with #20 enamel wire on a 1/2-inch fiberglass rod, subsequently covered with 1/2-inch shrink tubing to increase diameter to 3/4 inch. This configuration achieved resonance at 3965 kHz with a 5-foot stainless steel whip. The antenna integrates a matching transformer, identified by larger turns near the PL259 connector, and is constructed using a modified Radio Shack CB antenna base. Construction involves drilling and epoxying a 1/2-inch fiberglass rod into a PL259 connector, feeding #20 enamel wire through the rod, and winding 17 turns of #18 matching coil wire between the PL259 sleeve and the center feed point. The main loading coil fills the 2.5-foot rod section. The design allows the antenna to bend for garage clearance and emphasizes maintaining a 50-ohm feed impedance to prevent vehicle electrical damage. The author also discusses experiences with a Yaesu ATAS-100 motorized antenna and a 10-meter antenna project, noting issues with auto couplers and the ATAS-100's performance on 17 meters. Future modifications considered include adding a small servo for band spreading and increasing the fiberglass rod length for a 3-foot loading coil to improve bandwidth. The antenna's sharp tuning, between 3960 kHz and 3970 kHz, necessitates careful adjustment of coil turns for optimal VSWR.

The ZS6BKW wire antenna, a variant of the G5RV, utilizes a specific 13m (42.6 ft) length of 450-ohm window line as its matching section, feeding a 28.5m (93.5 ft) flat-top element. This design aims for lower SWR on 40m, 20m, 17m, 12m, and 10m compared to a standard G5RV, often achieving SWR values below 1.5:1 on these bands without an antenna tuner. The feedpoint impedance transformation provided by the window line allows for direct connection to 50-ohm coax on multiple bands. F4FHH's experience involved constructing the ZS6BKW and evaluating its performance against an _OCF dipole_ (Off-Center Fed) on various HF frequencies. The article includes observations on SWR readings and operational effectiveness, highlighting the ZS6BKW's suitability for multi-band operation. The antenna's overall length, including the flat-top and window line, is approximately **41.5 meters** (136 feet), making it a significant wire antenna for fixed station use. Comparative analysis with the OCF dipole provided practical insights into the ZS6BKW's advantages and limitations, particularly concerning bandwidth and tuner requirements.

This article describes the design of an antenna for local contacts on 7MHz, including a simple and efficient matching system that presents a 50 ohm load to the transceiver.

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.

This 1:49 transformer is used with wires any multiple of 1/2 wavelength. This is not a matching network, it's a wideband transformer and it has some advantages compared to LC matching

Presents the detailed construction of the _FLA25HV_ antenna, a specialized array optimized for Earth-Moon-Earth (EME) communications on the 2-meter band. This resource provides schematics and practical insights into building a high-gain antenna system capable of reflecting signals off the lunar surface, a challenging but rewarding aspect of amateur radio. It covers the mechanical and electrical considerations essential for achieving the precise pointing and signal strength required for successful moonbounce contacts, often yielding **20 dB** or more gain. Amateur radio operators pursuing EME operations require robust antenna systems and precise tracking capabilities. The FLA25HV design addresses these needs by focusing on element spacing, impedance matching, and structural integrity to withstand environmental factors while maintaining critical alignment for lunar reflections. Such systems are crucial for making contacts over distances exceeding **768,000 km**. This personal page serves as a practical guide for hams interested in constructing their own EME arrays, offering a glimpse into the technical dedication involved in pushing the boundaries of VHF/UHF propagation.

The antenna is an inexpensive, multiband, end fed HF antenna. It has a matching network consisting of a toroid core and an antenna lead of 30

A 90-foot vertical antenna constructed from **aluminum irrigation tubing** is detailed, focusing on its innovative raising and lowering mechanism. The resource describes a **45-foot ginpole** system, allowing a single operator to erect or lower the antenna in minutes. It covers the mechanical design, including the pivot base, insulated joints for the tubing sections, and guy wire attachment points. The antenna consists of two 30-foot sections of 4-inch tubing and one 30-foot section of 2-inch tubing, stacked with the smaller diameter at the top. The electrical design incorporates PVC "condulet" boxes at the 30-foot and 60-foot points, housing relays to change the effective height for multi-band operation on 160, 80, 40, and 30 meters. Ferrite rod inductive chokes are used for DC control and to tune out gap capacitance. The antenna is fed with 1000 feet of open wire line, connected to a matching transformer comprising stacked toroids and a coaxial/toroidal balun. Grounding is achieved with a 3x3 foot grid of 16-gauge tinned copper wires with soldered crossovers.

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.

Demonstrates the design and construction of a 9-element Yagi antenna for the **70 cm band** (432 MHz), based on the DK7ZB concept. The resource details EZNEC+ calculations for a single antenna, providing gain, sidelobe suppression, and front-to-back ratio figures. It also presents a comprehensive analysis of stacking two such antennas, including optimal stacking distance (1000 mm) and the resulting performance enhancements for the stacked array, such as an increased gain of 17.03 dBi. The article includes detailed drawings, wire file dimensions in millimeters, and azimuth/elevation plots for both single and stacked configurations. Practical construction steps are documented with original photographs, illustrating element mounting, the **28 Ohm matching system** using two quarter-wave 75 Ohm transmission lines, and the critical N-connector wiring. It also covers the iterative process of fine-tuning the driven element length to achieve a return loss of 20 dB, validating the EZNEC+ simulation results with actual measurements.

Gamma match antenna is an antenna 1/2 additional lambda with the impedance matching more flexible arrangements (var capacitor) by sliding through the gamma match/road.

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.

This project produces an inexpensive, multiband, end fed HF antenna matchbox, quick and easy to setup. This project creates a trifilar wound, 9:1 UNUN toroid matching transformer. Handles 100W and need an antenna tuner.

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.

Solves antenna matching problem with two phased antennas. Stacked rotary beams are popular. However, connecting two 50 Ohm antennas together presents some problems.

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.

The page discusses Axial-Mode Helical Antennas, focusing on turning helical antennas over perfect ground and modeling helices in NEC-2 for optimized design. It covers topics such as high-gain performance, broadband, impedance matching, radiation pattern, feedline, balun, near field, far field, and DIY applications.

A Moxon rectangle antenna design for the 11-meter band is presented, offering a compact and lightweight solution for directional HF DX operation. This two-element parasitic array, popular among amateur radio enthusiasts, provides considerable directional gain and lower noise on horizontal polarization. The design is suitable for both 27 MHz Citizens Band (CB) and the lower portion of the 28 MHz amateur radio band, making it versatile for operators interested in either service. Construction can utilize materials like bamboo, squid poles with wire elements, or aluminum tubing on a central boom. The article includes a plan view diagram with specific dimensions (A-E) in centimeters and inches for building the antenna, such as a 392.09 cm (154 3/8 inch) driven element. The Moxon configuration inherently presents a 50 Ohm load to the transceiver, often eliminating the need for an external matching unit or balun. Performance data for an antenna mounted at approximately 30 feet indicates a gain of 10-11 dBi and a frequency range of 27.300 MHz to 28.300 MHz. The design is noted for its excellent front-to-back rejection, with tested signal drop-offs from S5-S7 to S2 when turned, demonstrating effective suppression of unwanted signals.

A Half wave antenna has a high impedance feed point. This can be matched using a 1/4 wave stub matching section and converts the 40m vertical into an L-shaped 20m J-Pole antenna. The 300 ohm feeder used for this purpose must be kept away from the ground.

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.

Presents the design and performance of a 4-element wire Yagi antenna for the 40-meter band, building upon VE3VN's earlier 3-element switchable wire Yagi. The resource details the antenna's evolution, highlighting the transition from a 3-element to a 4-element configuration and the resulting improvements in gain and front-to-back ratio. It provides specific insights into the antenna's construction and expected operational characteristics. VE3VN shares insights from field results, noting the antenna's performance on 40 meters. The discussion includes the antenna's pattern and matching characteristics, crucial for any DXer or contester looking to optimize their signal on this popular HF band. The author's experience with the previous 3-element design informs the enhancements made to this 4-element iteration. The article includes a visual representation of the antenna's current view, offering a practical perspective on its physical layout. It serves as a valuable reference for hams considering a directional wire antenna for 7 MHz operations, demonstrating a practical approach to achieving enhanced directivity and gain.

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.

GW4ALG's _136 kHz Pages_ document the evolution of vertical antennas for the 2200m band, starting with a prototype mounted on a house wall. This initial design, despite achieving the first **395 km** GM-GW QSO, suffered from significant insulation breakdown, high RF losses due to proximity to the house, and difficult tuning adjustments. The author details the challenges of maintaining resonance and matching with a variometer in the loft, noting that adding three earth spikes offered no measurable improvement over a simple water tap connection. The subsequent experimental 12m vertical, relocated away from the house, significantly reduced dielectric losses and proved far more effective. This antenna enabled GW4ALG to set a world DX record on 136 kHz with a **1916 km** QSO to OH1TN, and an intra-UK record of **703 km** to GM3YXM/P. The resource further explores the use of helium-filled balloons to extend the vertical radiator, achieving heights up to 27m, typically 20m, for enhanced low-band performance. Practical advice on balloon types, inflation, and critical insulation between the wire and balloon is provided, emphasizing safety and avoiding arcing.

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.

Optimizing DX chasing efforts, this software provides a refined approach to monitoring the DXCluster. It allows operators to configure specific filtering criteria, ensuring that only relevant DX spots are displayed, thereby reducing clutter and focusing attention on desired entities or bands. The application integrates alarm functionalities, notifying the user when a spot matching their predefined parameters appears on the cluster, which is particularly useful for working rare DX or specific band slots. Spot supports both macOS and Windows operating systems, offering a cross-platform solution for a broad user base. Its design emphasizes user control over the displayed information, moving beyond a simple stream of cluster data to an actionable intelligence system for DXers. This client aims to streamline the process of identifying and pursuing DX opportunities. While the software was previously a commercial product, the developer, K3NC, has retired and made registration files for DXBase 2007 available for free, along with a utility to generate registration keys for that specific version. This allows continued use of the DXBase 2007 logging software, though it's important to note the 64-bit OS compatibility modification required for generated registration files.

The G5RV multiband HF antenna, designed by Louis Varney (G5RV) in 1946, is a popular compromise antenna offering good overall performance on most HF bands when paired with an external antenna tuner. The basic full-size G5RV measures 102 feet across the top for 80 through 10 meter operation and is fed at the center via a 34-foot low-loss feed-stub. This interaction between the radiating section and the feed-stub facilitates matching across 80-10 meters with a standard tuner, often eliminating the need for ladder line directly to the shack. The antenna's design center frequency is 14.150 MHz, configured as a 3/2-wave dipole on 20 meters, with its 102-foot length derived from long-wire antenna formulas. Construction details emphasize the matching section, which can be open wire, ladder line (window-type), or TV twin lead. Each type has a specific velocity factor (VF) affecting its physical length for an electrical half-wave on 14 MHz; for instance, open wire requires 33.7 feet (VF 0.97), ladder line 31.3 feet (VF 0.90), and TV twin lead 28.5 feet (VF 0.82). The article provides formulas for calculating these lengths and discusses the antenna's behavior on individual bands, from 3.5 MHz where it acts as a shortened dipole, to 28 MHz where it functions as two three-half-wave long-wire antennas fed in-phase. Practical construction notes include recommendations for vertical descent of the matching section, sealing the coax junction, providing strain relief, and winding a coaxial choke coil to mitigate common mode current. The resource also presents dimensions for double-size (204 ft) and half-size (51 ft) G5RV versions, along with their corresponding matching section lengths for various line types, making it a versatile reference for hams considering this classic wire antenna.

A 50-ohm 10W resistor forms the core of this portable QRP antenna, designed by _K0EMT_ for convenient operation on 160m and 80m. The construction involves soldering the resistor to a BNC connector, with one lead to ground and the other to the center conductor, then insulating the assembly. This minimalist design aims to provide a highly portable solution for low-band QRP operations, acknowledging the inherent trade-offs between antenna size and efficiency. Testing with an antenna analyzer revealed low SWR on both 160m and 80m, with a Yaesu FT-817 confirming good matching. While 40m and 30m showed higher SWR, the primary focus remains on the lower bands. The author successfully tested the antenna with **2.5W CW** output, demonstrating its practical application for QRP field operations where ease of deployment is paramount, even if it means sacrificing some **gain** compared to full-sized antennas.

The 5/8 vertical it quite popular and matching solutions can vary

how to make a gamma match for a antenna. The Gamma match is the most used matching device used for yagi beams.

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.

This article explores the performance of an unloaded elevated vertical, base matching and feed line as a multi-band HF antenna system.

ARRL's Logbook of the World (LoTW) system is a repository of log records submitted by users from around the world. When both participants in a QSO submit matching QSO records to LoTW, the result is a QSL that can be used for ARRL award credit.

Optimizing the ZS6BKW antenna for full HF band coverage often requires specific modifications beyond its standard configuration. This resource details several enhancements, beginning with a simple series capacitor to improve 80m SWR, a technique W5DXP found effective for permanent installation due to its minimal impact on higher bands. Further improvements include a 10-inch parallel open stub for 10m resonance, shifting the frequency to 28.4 MHz with an SWR of approximately 1.8:1, a practical solution for Technician class operators. The document then explores a switchable matching section, adding or subtracting one foot of ladder line at the 1:1 choke-balun, which significantly impacts higher frequency bands and eliminates the need for a tuner on 17m. W5DXP's _AIM-4170D_ antenna analyzer measurements confirm these effects. More advanced modifications involve a parallel capacitor for further 80m SWR reduction, requiring remote switching for multi-band operation, and relay-switched parallel capacitors at specific points on the 450-ohm matching section to achieve low SWR on 60m, 30m, and 15m. These detailed steps, including _Smith chart_ analyses for the challenging bands, aim to transform the ZS6BKW into a truly all-HF-band antenna, reflecting W5DXP's practical experience in antenna tuning.