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Theory and origins of W4RNL Asymmetrical Hatted Vertical Dipole AHVD for portable operations.

An EH Antenna for 14 MHz by EB3EMD based on an original project by F5SWN

Constructing a high-power 70cm solid-state amplifier presents unique challenges, particularly when aiming for 500 watts output using modern LDMOS devices. This resource details the author's experience building a 70cm amplifier based on a _Freescale MRFE6VP5600H_ transistor, initially from an RFHAM kit. It meticulously outlines the necessary modifications to achieve advertised performance, including optimizing input and output matching, correcting bias circuitry, and ensuring proper output balun connections for stability. The author shares specific adjustments, such as trimming the prototyping board for better transistor fit, drilling additional mounting holes for improved heat sinking, and replacing original matching capacitors with a single _20pf MIN02 metal mica_ for superior output. A critical fix involved jumpering gate decoupling pads to balance the push-pull transistor halves, which increased output to 580W and improved IMD. The resource also highlights a crucial correction to the output balun connection, initially reversed in the _Dubus_ article schematic, which resolved intermittent stability issues. Test results are provided, showing input power, output power, and drain current at 50V, demonstrating the amplifier's performance after modifications. This practical account offers valuable insights for hams undertaking similar high-power UHF amplifier projects, especially those working with LDMOS devices and kit-based constructions.

A DIY Automatic Band Decoder (ABD) project, designed for dual-radio operation, addresses the common challenge of integrating band data with older transceivers lacking dedicated outputs. This particular build utilizes an AVR AT90S8515 microcontroller and a 16x2 Liquid Crystal Display (LCD) to provide band information, specifically targeting Kenwood rigs via a computer's LPT port. The design aims for cost-effectiveness while maintaining functionality, offering a solution for hams seeking to add automatic band switching capabilities to their station without significant expense. The project outlines the core components required, including the microcontroller, LCD, and an enclosure, noting that the Printed Circuit Board (PCB) fabrication and AVR programming might present challenges for some builders. It details the input requirements, such as a four-pin input and PTT for each radio, along with a 13.8V DC power supply. The decoder provides 2x6 outputs capable of sinking 500mA, suitable for controlling external devices like antenna switches or filters. Despite the original unit being damaged by a lightning strike in 2004, the author confirms its successful operation prior to the incident and mentions plans for a revised version. The resource includes a schematic in PDF format and images of the finished PCB and assembled unit, demonstrating the practical implementation of the design.

Originally eveloped by I1FLC, uses seven plug in coils covering 3.0 to 30Mhz in a Colpitts oscillator circuit.

Thierry LOMBRY, ON4SKY, develops in depth and with original pictures the long history of amateur radio all through the world from 900 BC to date.

An introduction to RDF contesting in southern California, updated from a paper originally submitted for Proceedings of the 1992 West Coast VHF/UHF Conference.

The Frankford Radio Club originated in the Frankford High School, in Philadelphia, around 1927.

The _Sci.Electronics FAQ: Repair: RFI/EMI Info_ document, authored by Daniel 9V1ZV, provides a detailed analysis of computer-generated RFI/EMI, focusing on its impact on radio reception. It identifies common RFI sources such as CPU clock rates (e.g., 4.77 MHz to 80 MHz), video card oscillators (e.g., 14.316 MHz), and even keyboard microprocessors, all of which generate square-wave harmonics across HF and L-VHF regions. The resource outlines a systematic procedure for pinpointing RFI origins, including disconnecting peripherals and using a portable AM/SW receiver with a ferrite rod antenna to localize strong interference sources. The document categorizes RFI mitigation into shielding, filtering, and design problems, offering practical solutions for each. It recommends applying conductive sprays like _EMI-LAC_ or _EMV-LACK_ to plastic casings of radios, monitors, and CPUs to create effective Faraday cages, emphasizing proper grounding and avoiding short circuits. For filtering, the guide suggests using line filters, ferrite beads, and toroids on power and data lines, and small value capacitors (e.g., 0.01 uF for serial/parallel, 100 pF for video) to shunt RFI to ground. It also discusses the use of bandpass, high-pass, low-pass, and notch filters on the receiver front-end or antenna feed to combat specific in-band noise.

This is a QST Article published in January 1982 by W1FB D. Demaw and HH Beverage and is a complete review of the original article published in 1922, which updates and reivew the beverage antenna theory and developlment, explaining the antenna design of transformers and gives accurate reports on antenna general performance.

PACTOR-II is a fully backward-compatible improvement to the original PACTOR system. It is an adaptive mode that applies different modulation and encoding methods depending on the channel quality.

Modification leaves nearly all of the existing Omni agc circuitry intact, simply add an audio detector which modifies the delay characteristics of the original system by G3IXQ

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.

A homemade band pass filter for the 30 meter band based on the original VE7BPO design

This online project guide details the construction of a homebrew boom microphone system. It details the assembly of a microphone shell from a 3/4" PVC pipe section and an end cap, requiring a drilled hole for a snug fit of the electret or condenser mic element. The internal wiring schematic specifies a **2.2 K** resistor and a **47 uF** polar capacitor for signal conditioning, with a circuit diagram provided for integration with IC-706 series transceivers. The guide outlines the use of CAT-5 cable for internal connections, incorporating strain relief at the rear of the mic shell, and an inline 3.5 mm jack to facilitate an external _PTT_ line, designed for a foot-mounted switch. Further construction involves fabricating a microphone shock mount from a 2-inch PVC connector, detailing the creation of four "fingers" and the insertion of screw-eyes for attaching elastic bands, which are twisted 180 degrees for tensioning and vibration isolation. A foam wind screen is also incorporated into the microphone assembly, secured with adhesive. The boom arm itself is repurposed from an articulated architect lamp, with the original lamp assembly converted into a **60 watt** resistive load for testing power sources. Microphone cabling is secured to the boom arm using wire ties, ensuring sufficient slack at hinge points to maintain articulation. The boom base is mounted to a bookshelf, requiring specific positioning to achieve proper microphone placement in front of the operator. Performance evaluation of the microphone system is conducted through on-air audio signal reports from other amateur radio operators. DXZone Focus: Online Project Guide | Boom Microphone Construction | Electret Mic Element | PTT Line

Demonstrates a specialized DX cluster monitoring application, _DxWatcher_, designed for Windows environments. It processes DX spots received via Telnet/Internet, presenting them in a filtered table and a dynamic bandmap. The software integrates with transceivers, specifically the FT-2000, to read VFO frequency and enable one-click tuning to spotted stations. _DxWatcher_ version 1.0.3.0, released on 13 June 2020, includes minor bugfixes and improvements such as enhanced recovery from suspend mode. Key features include configurable bandmap position and size, automatic opening, and bolding of spots received within the last **10 minutes**. The application utilizes the standard _ctry.dat_ file for DXCC country analysis, allowing users to update it for current DXCC status. Source code, developed in C# with MS Visual Studio 2008, is freely available, encouraging modification and sharing while requesting retention of the original author's callsign.

Investigates the legal framework surrounding **pneumatic antenna launchers** in Victoria, Australia, specifically their classification under the Firearms Act 1996. The author, VK3KBC, details how these devices, designed to discharge a projectile by compressed air, are defined as 'firearms' and subsequently categorized as **Category E Longarms**. This classification carries significant penalties for unregistered possession or use, with the author noting the lack of provisions for amateur radio operators to legally possess and use such devices for antenna deployment. The author shares personal experiences needing such devices for portable HF radio operations, contrasting them with previously legal slingshots and current alternatives like kites or bow and arrow. VK3KBC outlines efforts to advocate for legislative change, including submissions to the Wireless Institute of Australia (WIA) and the Victorian Department of Justice, proposing an amendment to Section 3(i) of the Firearms Act 1996 to include amateur radio field operations as an exempted use. The resource also reviews the original intent of the Category E firearm classification, suggesting that pneumatic antenna launchers may have been assigned this category in the absence of a more suitable alternative.

Jefferson Amateur Radio Club JARC was originally founded in 1956. We're located just outside of New Orleans, Louisiana in the suburb of Metairie

The requested resource, identified by the title "Micamold XTR" and description referencing the _Micamold XTR-1_ transmitter manufactured in 1948 by MICAMOLD Radio Corp., is currently unavailable, returning a 404 error. This indicates the specific content detailing the vintage radio equipment, its technical specifications, or historical context is not present at the given URL. The original intent was likely to provide information on this particular piece of antique radio gear, potentially covering its design, operation, or restoration aspects relevant to collectors and enthusiasts of historical amateur radio equipment. The absence of the page means no technical details, schematics, or operational insights regarding the _XTR-1_ transmitter can be retrieved. Users seeking information on this specific "boat anchor" radio would need to pursue alternative sources or attempt to contact the original website owner directly, as suggested by the QSL.net error message. The QSL.net platform, which hosts over 30,000 individual amateur radio websites, provides free services but does not maintain the content of individual hosted pages.

This resource, intended to present historical score records for the _ARRL International DX Contest_, currently displays a "Page not found" error. The page's original purpose was to document top scores and records for both Phone and CW segments of the contest, offering a historical perspective on competitive amateur radio operating. Without the content, no specific technical details regarding past contest results, callsigns of record holders, or score breakdowns can be extracted. The resource's current state prevents any analysis of score comparisons, operational strategies of top stations, or the evolution of contest performance over time.

Indexes over 100 digitized amateur radio callbooks, primarily from the early to mid-20th century, providing a historical record of callsign assignments and licensee data. The collection facilitates research into past amateur radio operations, tracing callsign lineage, and identifying operators from specific eras. Each entry typically includes the callsign, licensee name, and geographic location as published in the original printed volumes. Users can browse the collection by publication date or utilize the search function to locate specific callsigns or names within the archived documents. The resource serves as a valuable repository for historical amateur radio data, supporting genealogical and operational research. Access to these scanned documents is provided directly through the Internet Archive platform, ensuring long-term preservation and availability of these historical amateur radio records.

GUI for the KK7KA Wolf software, that was originally written as command line interface only. Wolf is a weak signal software

Moxon is a rectangle shaped directional antenna, originally designed by Les Moxon G6XN. There are couple of advantages of using this antenna. It is small in size, Easy to mast, Balanced to 50 Ohms, Near 1:1 SWR, Excellent Front to Back (F/B) ratio, Large bandwidth

Original article was in December, 1986 QST

A synthesized 2.3 GHz Amateur Television (ATV) transmitter design, conceived by Ian G6TVJ, is presented, targeting broadcast-quality video performance on the 13cm band and extending up to 2.6 GHz. The core of the design utilizes a commercial Z-comm Voltage Controlled Oscillator (VCO) that tunes from 2.2-2.7 GHz, providing a +10 dBm output and simplifying RF alignment. This VCO's stability, originally intended for narrowband applications, readily accepts high-frequency video modulation, contributing to the transmitter's robust performance. The exciter stage, incorporating a Mini Circuits VNA 25 MMIC amplifier, boosts the signal to +16dBm, while a Plessey SP4982 prescaler divides the output frequency for the synthesizer. The synthesizer employs a Motorola MC145151 CMOS parallel IC, favored over the common Plessey SP5060 for its superior video modulation characteristics and ease of programming without microprocessors. This choice addresses issues like LF tilt and distorted field syncs often seen with SP5060 designs, particularly when operating through repeaters or over long distances. The MC145151 divides the signal further, enabling precise frequency stepping, with programming handled by EPROMs for channel selection and LED display. The loop filter network, critical for video integrity, was developed through experimentation to prevent the PLL from reacting to video modulation, ensuring a clean transmitted picture. The transmitter incorporates a Down East Microwave commercial power amplifier module, delivering approximately 1.6W output, driven by the exciter through a 3dB attenuator. Construction involves surface-mount SHF components on micro-strip lines etched onto double-sided fiberglass board, housed within a tinplate box. The design boasts no AC coupling in the video path, preserving low-frequency response, a common failing in other ATV transmitters. Performance tests with a 50Hz square wave revealed no LF distortion, and a calibrated "Pulse & Bar" signal showed a near 100% HF response, demonstrating its capability for high-quality ATV transmissions.

A Microvert antenna by KD5RVX based on the original microvert concept by DL7PE. PDF includes a 20 foot portable PVC tower project

A 7 dB directional gain is reported for this portable VHF Yagi antenna design, which utilizes cut metal tape measure sections for its elements. The resource details the construction process for a 2-meter band antenna, emphasizing its ease of build and portability. It specifically mentions the design's suitability for radio direction finding (RDF), fox hunting, and communication with satellites and the International Space Station (ISS), highlighting its practical applications for amateur radio operators. The construction cost is estimated at under $20, with potential for even lower expense if salvaged materials like old tape measures and PVC pipes are used. The article references _Joe Leggio's_ (WB2HOL) original design, noting specific alterations made by the author. It also compares this design to other DIY Yagi antennas, including _FN64's_ 2-meter band and _manuka's_ 70-cm band tape measure Yagis, underscoring its unique combination of simplicity, portability, and effective performance with a 1:1 SWR achievable on the 2-meter band.

Documents the construction of a **VHF/UHF** antenna addition for the Buddipole HF antenna system, leveraging the existing Versa-Tee component. The project details the fabrication of a custom antenna mount from angle aluminum, including specific drilling and tapping for 3/16"-24 bolts, and the creation of radials from Simpson Strong Tie Insulation Supports. It specifies radial lengths for 70 centimeters (6 inches from the center stud) and 2 meters (19 1/4 inches), noting the use of wire nuts for safety. The resource outlines the construction of a mast from 1/2" ID PVC conduit, connected with 3/8"-24 connecting nuts and bolts, mirroring the Buddipole's modular design. It describes the integration of a mobile dual-band antenna with a 3/8"-24 mounting stud and the custom coax setup with BNC and **PL-259** connectors. Field testing with an FT-817ND and a separate dual-band SWR meter confirmed good SWR on both 2 meters and the 440-450 MHz section of 70 centimeters, with positive reception reports during Field Day activities. Further, the article describes the creation of a custom carrying solution, including a 22-inch tripod bag and a fabric roll-up, to emulate the portability of the original Buddipole system.

Encouragement for Little Pistols, article originally written for and published in SKIP the monthly newsletter of the Fresno Amateur Radio Club

An interesting presetnation full of usefull tricks to correctly design and build 23 cm Yagi using simple tools. The basic design of the antenna presented in this document is taken from the original DL6WU Yagi Design published in 1982

Mobile RFI, often manifesting as persistent noise in the receiver even with the antenna disconnected, frequently originates from the vehicle's power supply system. This guide details systematic troubleshooting steps, beginning with isolating the radio from the car's 12-volt supply to confirm the power system as the noise source. It emphasizes the critical importance of drawing power directly from the battery using **heavy gauge wire**, bypassing the fuse block to leverage the battery's natural capacitance for RFI suppression and ensuring a solid RF ground. Proper routing of power lines through the firewall is also covered, advocating for dedicated grommeted holes to prevent inductive coupling from other wiring harnesses. The article stresses the necessity of fusing both positive and negative leads from the battery, a crucial safety measure to prevent damage to the rig and mitigate high-current risks should the battery's engine block ground become compromised during service. Addressing **alternator whine**, a common high-pitched noise that varies with engine speed, the resource suggests checking battery connections and the alternator-to-battery harness for looseness or corrosion. It also mentions the utility of adding an external RF noise suppression capacitor in parallel with the alternator's internal capacitor for enhanced filtering, and the effectiveness of commercially available in-line power supply filters.

The problem originates by improper TXOUT-to-RF timing (RF transmission exists still after a TX-EN prohibition), combined by too long decay of their CW pulses.

The Alpha-Delta group is a group dedicated 100% to DX Oncemetros in the band and can say that is 100% of Mexican origin.

Taken from April 1935 issue of QST page 60 where there is a short article on the origin of 73

Noise Canceller kit originally developed about 1989 by G4WMX and GW3DIX and improved by DK9NL and DG0KW.The VK5TM Noise Canceller is another version of the design, with the HF Vox circuit removed and a couple of other minor changes, including the use of SMD JFETs and a double-sided pcb.

The Noantri WebCLX presents real-time DX spots, including frequency, DX callsign, country, and comments, facilitating active DXing and contesting. It operates as a web-based cluster, offering an alternative to traditional Telnet clusters for accessing spotting data. The interface displays current UTC, allowing operators to track propagation and activity across various amateur bands. This service is maintained by the _Noantri DX Group ARI Roma_, indicating its origin within the Italian amateur radio community. It supports the dynamic exchange of DX information, crucial for operators seeking new entities or participating in competitive events. Key features include the display of spots for modes like FT8, and it functions as a DXSpider-based system, providing a robust platform for **DX spotting** and **propagation analysis**.

The formatting of the address on an international item is dictated by the recommendations issued by the countries of origin and destination of the item.

Sams Photofact download Schematics and Service Manuals, Originals and downloads.

The Nashoba Valley Amateur Radio Club (NVARC) was formed in Groton, Massachusetts, in the spring of 1992 and has grown from the original 13 founders to over 60 members.

The W1HP Philips Amateur Radio Club, originally the Hewlett-Packard ARC, has a history rooted in Andover, Massachusetts, as an employer-sponsored club. It evolved from a "full-service" club to primarily a Field Day club, maintaining its focus on this major annual effort. The club has participated in Field Day under various configurations, including W1HP/1B in Arizona, and has partnered with K1KKM and utilized GOTA stations like K1KKM and KD1NA. Recent Field Day operations reflect adaptations to changing circumstances, with members operating individually due to COVID-19 and later under "new" ARRL rules, sometimes as a "distributed" club. The club's constitution is also referenced, providing insight into its foundational structure. This page is maintained by W1DYJ, with a last update noted as 9 December 2025.

Founded by a small group of young hams in East St. Louis, Illinois, the W9AIU Egyptian Radio Club serves as a local amateur radio organization. The club's origins trace back to meetings held in Herb Wilhelm's, W9APX, dry cleaning shop, indicating a grassroots beginning for this community group. It operates as a typical ham radio club, fostering camaraderie and likely supporting various aspects of the hobby for its members. As an amateur radio club, W9AIU likely engages in activities such as local nets, field day operations, and perhaps provides licensing support or technical discussions. Such clubs are crucial for new hams seeking mentorship and for experienced operators looking to participate in group activities like contesting or public service communications. The club's presence in Illinois suggests a focus on local and regional amateur radio initiatives.

OpenHamClock is a modern, open-source dashboard for amateur radio operators, designed as a web-based successor to the original HamClock. Deployable locally on a Raspberry Pi or via the cloud, it centralizes essential DX operations into a single, intuitive interface. At its core is an interactive world map that visualizes real-time DX spots, signal paths, satellite tracking, and POTA activators. The software seamlessly integrates critical tools like WSJT-X, DX Cluster, and PSKReporter for monitoring digital traffic. Additionally, it provides vital environmental data, including real-time space weather indices, solar activity, and personalized HF propagation predictions. With customizable themes and a modular architecture, OpenHamClock offers modern operators comprehensive, at-a-glance situational awareness of global radio conditions

Sleeping tecniques during contest operations. This article originally appeared in the National Contest Journal.

The MFJ-971 portable antenna tuner, as stock, lacks a bypass switch and sufficient inductance for efficient 1.8 MHz operation. This modification addresses these limitations by integrating a DPDT switch for direct signal bypass, enhancing operational flexibility. Furthermore, the guide details the addition of a T130-2 iron powder toroid, wound with **29 turns** of enamelled copper wire, to augment the tuner's internal inductance. This increases the maximum inductance from approximately 17µH to around **27µH**, enabling effective impedance matching on the _160-meter band_. The modification involves cutting the wire after the 'L' tap on the original inductor and inserting the additional toroid, ensuring the entire original coil plus the new inductance is engaged when 'L' is selected. This preserves the functionality of other inductance settings while extending low-band performance. The article also highlights a potential RF burn hazard from the variable capacitor nuts on the MFJ-971, even at QRP power levels.

A classic document originally presented in Proceedings of the Institute of Radio Engineers in 1937 and is, still today, the standard referenced by the FCC, text books and many amateur radio publications.

A travel, or a fixed vertical coax antenna originally designed by PA0FBK. This antenna is very easy to make from a piece of 50 ohm or 75 ohm coaxial cable, and can be either smooth, roll-up version, or rigid cable

Maintaining vintage Eddystone receivers often presents unique challenges, as detailed by Victor Jenkins in his refurbishment of an EA12, where his deep understanding of RF circuits ensures optimal performance for daily shortwave listening. Similarly, Gerry O’Hara VE7GUH, a prolific contributor to the EUG website and a trustee, meticulously documented his restoration of an Eddystone S830/2, even addressing an unusual instability issue with a follow-up postscript article and YouTube videos demonstrating the fix. His work, along with numerous other articles on the "Restorations" page, showcases a master's approach to bringing vintage sets back to factory specifications or better. Beyond technical restorations, the EUG also shares compelling historical narratives. One such story recounts the discovery of a long-lost 78rpm recording featuring Eddystone Radio Ltd.'s founder, George Stratton Laughton, and other key figures discussing the company's wartime and post-war contributions to shortwave communications. This six-minute BBC production, transcribed into an MP3 file by Peter Carney, offers a rare auditory glimpse into the company's legacy, highlighting its role in supplying equipment to police, ministries, and expatriate British workers. The community aspect thrives through shared experiences, like Roger Trickett's anecdote about his Eddystone EC10, which has been continuously powered for 50 of its 54 years, traveling across continents and enduring various modifications. Another intriguing account from Roy GM4VKI details the "S640 Identity Crisis," where a seemingly standard S640 receiver turned out to be a masterfully engineered 80/20-meter SSB transceiver built into the original chassis by GI3ZX, showcasing incredible ingenuity from a bygone era of amateur radio.

Homemade RF limiter project, to protect the K3 receiver front-end for high radiofrequency based on the original KD9SV project.

Original User Manual for the Baofeng UV5R

Virgo is originally designed to serve for meteorscatter propagation purposes in amateur radio. Maintained by Bastian, DB1BM, and Alexander, DL8AAU. Virgo is a projection of the sky visible at your location. Different to other astronomical sky views, there are no stars displayed, but the radiants of current meteor showers.