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A further study of the spurious emissions from an FT847 on 70 MHz by G7CNF

DC filters from radius power are specifically optimized for applications with DC supply like e.g. photovoltaic inverters. Radius Power provides total power solutions, EMI filters solutions from design to manufacturing, Three Phase, Single Phase, Power Line, IEC inlet, Power entry modules Filters.

OEMSEMI is an independent distributor for electronic components, offering worldwide spot components supply service and solutions to obsolete components supply.

Liberia 2011 5M2TT DX Pedition Official web site

The Vibroplex Collector’s Page details the history and identification of Vibroplex semi-automatic telegraph keys, commonly known as "bugs." It traces the evolution from Horace G. Martin's 1902 Autoplex, which required a battery, to the fully mechanical Vibroplex patented in 1904. The resource explains how these keys generate automatic dots and manual dashes, helping telegraphers mitigate Repetitive Motion Disorder (RMD) and increase sending speed, thus improving their earnings. The site also covers the initial design by Alfred Vail in 1844, Jesse Bunnell's 1881 "Triumph Key," and William O. Coffe's 1904 "Mecograph." This page assists owners in identifying their Vibroplex models and determining their manufacturing dates, providing insights into the company's long history and notable figures like J. E. Albright. It notes that approximately 300,000 Vibroplexes have been produced since 1904, with the Original model still in production after more than 90 years. The resource also touches upon various Vibroplex models, including unusual, scarce, and common types, alongside legal and illegal clones from other manufacturers.

A list of links to semiconductor manufacturers, including direct links to their datasheets index page

Online NOS electronic parts shop for QRP-QRPp radio constructors, to vintage radio and electrical measuring equipment restaurators. Many Germanium diodes, transistors and RF parts, semiconductors.

Grupo de radio emissao mensageiros da Paz

Determining the characteristic impedance (Z) of an unknown coaxial cable, a common challenge for many radio amateurs, can be resolved with a straightforward method. The impedance of a coaxial cable is derived from its inductance and capacitance, and importantly, these values are independent of the cable's length or the operating frequency. This means that measuring a random length of cable, such as 20 meters, provides sufficient data for calculation. The core of this technique involves an LC-meter to obtain the inductance (L) in microHenries (uH) and capacitance (C) in microFarads (uF). The impedance is then calculated using the formula Z = L/C. For instance, a measurement yielding L=1.2uH and C=450pF (0.00045 uF) results in an impedance of 51.6 Ohms, closely matching **RG-58** specifications. Similarly, a TV coaxial cable with L=1.8uH and C=320pF (0.00032 uF) calculates to 75 Ohms. While the accuracy of this method, depending on the LC-meter's tolerance, is approximately 10%, it proves sufficiently precise for practical determination of unknown coaxial cable impedance, as noted by Makis, SV1BSX, who credits Cliff, K7RR, for the formula's dissemination.

Online shop for electronic components, sensors, connectors, capacitors, resistors, passives, semiconductors from Baitron independent electronic components distributor.

Constructing a dual-band antenna for 40 and 20 meters often involves compromises in size or complexity. This resource presents a compact _open sleeve dipole_ design that addresses these challenges by using 450-ohm ladder line and folded elements to achieve a total length of approximately **17.17 meters**, significantly shorter than a full-size 40-meter dipole. The design leverages electromagnetic coupling, where a primary radiator handles the 40-meter band, and a second conductor resonates on 20 meters without direct electrical connection. This configuration eliminates the need for traditional traps, loading coils, or switching components, simplifying construction and reducing potential loss points. The antenna is fed with RG-58C/U coaxial cable, and a common-mode choke is recommended at the feed point to suppress sheath currents, ensuring a cleaner radiation pattern and minimizing RF in the shack. The design is well-suited for portable operations, field deployments, temporary installations, and restricted urban environments where space is a premium, offering solid performance on both HF bands.

How to solve RFI problems caused by the charge controller, which is a PWM type charge controller, that generates a lot of EMI interference

A news site focused on DXing and contesting, DXNews.com provides daily updates on upcoming **DXpeditions**, contest announcements, and general **amateur radio news**. The site features a continuously updated feed of articles detailing call signs, operating dates, IOTA references, and specific contest participation plans for various DX operations. Content includes detailed reports on planned activities from rare and semi-rare DX entities, often with information on operators, bands, modes, and QSL routes. It also covers major amateur radio contests, offering insights into rules, participating stations, and results. The archive depth extends back many years, providing a comprehensive historical record of DX activity. This resource is ideal for experienced DXers and contesters seeking timely information to plan their operating schedules, track rare DX entities, and stay informed about the global DX scene. It also serves general amateur radio operators interested in following significant events and operations within the DX community.

TRS RenTelco provides new or used electronic test equipment for rent, lease or purchase. Solutions are provided for various type of equipment such as spectrum analyzers, network analyzers, oscilloscopes etc from leading manufacturers. Our products are widely used in communications, R&D, semiconductor, and wireless industries.

Premium Contest resort from Montenegro

A table that summarize all known amateur radio emission modes, with reference to software and platform available for digital modes

For my SOTA activities, i recently bought a QRP transceiver QRP SW-3B, which is a three-band QRP CW only for 40/30/20 m. So, i needed an antenna that would allow to use these 3 bands in SOTA portable activity. Already having some experience with the EFHW antenna, i decided to build one for 40/30/20m.

The _RS Group_ (formerly Distrelec) provides a comprehensive online store for electronic components, catering to both industrial and amateur radio needs. This resource offers a wide array of parts, including semiconductors, capacitors, resistors, relays, sensors, and power supplies, essential for constructing and maintaining amateur radio equipment. The platform emphasizes efficient procurement and features various top-level categories for easy navigation, such as **Sensors** with 33 subcategories and **Relays** with 13 subcategories, supporting diverse project requirements. Beyond component sales, RS Group offers services like ISO- and DAkkS-certified calibration for over a thousand measuring devices, and e-procurement solutions for businesses. The site also promotes _DesignSpark_, a community and software suite for electronic designers, aiding in the realization of design ideas. This integration aims to provide enhanced local support and a broader product selection, facilitating everything from basic circuit builds to complex industrial automation projects.

A premier club that brings out the very best in Amateur Radio around the Sheffield area

Chirikof Island DXpedition IOTA NA-235 Semidi Islands Group

I have RFI, now what– Locating it. This article is the first of a three parts article, that covers the problem of locating the RFI source. Author make use of an SDR receiver to locate RFI emissions. Ai interesting RFI location process diagrams helps on following the various phases, permitting the discovery of almost 75% of the RFI issues.

The Hurricane Watch Net (HWN) is an amateur radio organization dedicated to serving the National Hurricane Center and the public since 1965. It plays a crucial role in disseminating real-time tropical weather information for the Atlantic and Eastern Pacific regions. The HWN operates during hurricane events, providing updates and facilitating communication among amateur radio operators and emergency services. This network is essential for ensuring that communities are informed and prepared for severe weather conditions. In addition to its operational role, the HWN offers educational resources and outreach programs aimed at enhancing public awareness about hurricane preparedness. This includes providing access to tracking maps, storm surge information, and safety guidelines. The HWN encourages amateur radio operators to participate in its activities, fostering a spirit of community and collaboration in the face of natural disasters. By subscribing to their email updates, individuals can stay informed about active storms and receive vital safety information.

An overview of the development of the Morse key for sending the Morse Code, from the first camelback keys, through straight keys and sideswiper keys to the semi automatic keyers including the Vibroplex to the modern electronic keyer.

Details the custom manufacturing of high-performance RF coaxial cable assemblies, emphasizing the use of _Times Microwave_ and other premium U.S.-made components. The company operates as a Small Business within the Albany, GA, HUB ZONE, with all warehousing and production facilities located in Southern Georgia, approximately 150 miles south of Atlanta. MPD Digital specializes in bespoke cable solutions for diverse applications, including amateur radio, WiFi, satellite, and cellular systems. Highlights the availability of thousands of connector configurations, supported by expert engineers on staff. The facility's total plant area and commitment to rapid shipping on custom cable assembly orders are noted. A specific product, the _MPD-400PVC Super Flex Coaxial Cable_, is mentioned as a recent update.

Official web site of LA1K / LA1ARK / LA1UKA Akademisk Radioklubb

The weather station described here uses a TTGO v3 1.6.2 module and various sensors. It displays the data on an OLED screen and transmits them among a choice of protocols to the APRS, APRS-IS, Wunderground servers or via an MQTT broker. APRS data is transmitted on 433.775 MHz (can be changed) using the LoRa protocol. APRS beacons picked up by iGate gateways are then transmitted to APRS servers.

This webpage explains how analog wide area two way radio systems were setup by various states before systems like VIPER, PALMETTO 800, or FLEETNET were established.

The Maine QSO Party is designed to encourage Maine stations to expand their knowledge of DX propagation on the HF and MF bands, improve their operating skills, and improve station capability by creating a competition in which W/VE, and DX stations have the incentive to work Maine. The MEQP is Maine's Premier International HF Contest.

Low Cost Satellite Antennas article was originally presented at a Project OSCAR seminar on September 30th, 1990. AMSAT-UK printed an abridged version of this presentation in their OSCAR News, Number 88, April 1991. The original presentation has been reedited and updated for AMSAT's Web page.

This innovative antenna tuning unit (ATU) enables QRP operators to match their antennas without transmitting RF signals. Using a noise bridge technique instead of traditional transmit-and-tune methods, it achieves truly silent operation. The design incorporates an L-match network with switched inductors and variable capacitor, handling impedance matching from 3-30MHz. Operating from a 9V battery, it includes a built-in RF power meter and dummy load for QRP transmitter testing. The compact unit is particularly suitable for portable operations where minimal RF emissions during tuning are desired.

The Score Distributor facilitates real-time score forwarding for amateur radio contests, automatically transmitting data from various logging software to multiple online scoreboards. By configuring logging applications to send score data to the Distributor, operators ensure their current score is simultaneously represented on platforms like the _Contest Online ScoreBoard_ (COSB) and the Live Contest Score Server by R4WW. This system eliminates the need to choose a single scoreboard, providing broader visibility for participants. This utility enhances the competitive experience by allowing contesters to monitor their performance against other stations throughout an event. Observing real-time standings can provide significant motivation, particularly during periods of challenging propagation or when striving to maintain pace with club members or peers. The platform supports almost all major contest logging software, simplifying integration for a wide range of operators. Developed by WA7BNM, the Score Distributor was last revised on June 14, 2023. It aggregates score data, offering a unified point of submission that then disseminates the information, ensuring a **single point of entry** for broad scoreboard coverage and improving the dynamic feedback loop for participants.

In order to understand, however imperfectly, when the band will open, it is essential to have some understanding of why the band will open. Article by J. R. Kennedy K6MIO/KH6, Gemini Observatory Hilo, Hawaii

Showcasing German engineering, ANjo Antennen develops and manufactures a diverse portfolio of amateur radio and commercial antenna products. Their offerings span a wide frequency range from 1.8 MHz to 3000 MHz, emphasizing electrical and mechanical precision for longevity. The company actively participates in events like FUNK.TAG Kassel, providing opportunities for direct engagement and order pickup. ANjo's product line includes high-performance **Yagi antennas** optimized for Tropo and EME, along with multi-stacked Quad antennas designed for contest operations, featuring wide horizontal and narrow vertical beamwidths. They also produce circularly polarized satellite antennas, some with switchable LHCP/RHCP, leveraging their commercial satellite antenna expertise. Beyond amateur applications, ANjo provides flexible, custom antenna solutions for commercial sectors such as BOS, EMC measurements, and telemetry. Their commitment to quality is evident in the Premium-Line antennas, which utilize **1.4301 (V2A) stainless steel** for mast clamps and connectors, ensuring durability and corrosion resistance. They also offer end-fed HF multiband wire antennas, known for their compact footprint and discreet installation.

Affordable full color QSL card printing. Premium quality offset printing with gloss, spot UV, and foil coatings.

SW Keyer for remote operations. This is a simple tool based on the Morse Code Iambic and Semi-Automatic Keyer from the Morse-Code-Tools projects. You can use your key, bug or Iambic Paddle stright connected to your personal computer without a hardware morse keyer.

A home made project for a 7 element yagi antenna for the two meters band based on the DK7ZB original desing.

The *SPACE* Amateur Radio over Internet Protocol (RoIP) system offers public audio transmissions from NASA Mission Control and astronauts, primarily for educational purposes. This service streams NASA public media sources, including *Artemis II* and the ISS public audio channel 2 feed, which predominantly features English communications. Astronaut activities on the ISS typically occur between 0700 UTC and 19:00 UTC, with transmissions most common during early mornings USA time, alongside special events such as launches or spacewalks. Users can connect to the live stream via EchoLink to the *SPACE* conference, via IRLP to the 0100 experimental reflector, or via Allstar to node 516221. EchoLink connections utilize the GSM CODEC, while IRLP and other connections default to uncompressed or u-law CODEC. The service notes that long periods of silence are common, and NASA audio sources can be periodically unavailable or noisy. Daily recordings of these transmissions are published at space.rfnet.link/recordings/, available as .ogg audio files for direct playback or .m3u8 playlist files for network streaming in applications like VLC. Each playlist file provides a list of timestamped audio transmissions, allowing users to review specific segments of interest.

This keyer being intended to be used mainly in conjunction with contest software. This keyer is based on an Arduino Nano and the Keyer software by K3NG. It has been designed with very basic features, and it is intended to work with logging software.

Direct conversion receivers (DCR) are gaining renewed interest due to advancements in semiconductor technologies and their suitability for integration in compact, low-cost, multi-standard applications. Unlike traditional superheterodyne receivers, DCR eliminates image frequencies and bulky off-chip filters but introduces challenges like DC offsets, nonlinearity, and noise issues. This tutorial explores DCR's historical development, compares it with other receiver architectures, and addresses its inherent obstacles. DCR's potential for integration and compatibility with software-defined radio highlights its role in modern communication systems despite its technical complexities.

Stop EMI RFI Interference in Off Grid Solar PV Systems, in this article the author provides hints on tracking down the EMI or RFI source, shielding and grounding in order to eliminate interferences on the whole HF and VHF ham radio bands

How to use a small USB DJ controller to remote control the Kenwood TS-590s

In this study, the author builds upon Muncy's research, demonstrating that radio-frequency current on cable shields affects audio systems through the "pin 1 problem" and shield-current-induced noise (SCIN). An enhanced equivalent circuit for ferrite chokes is proposed, addressing dimensional resonance and inductor self-resonance. Field tests confirm that chokes reduce interference across 500 kHz to 1,000 MHz. Guidelines for diagnosing and mitigating EMI from various sources are provided for product development and field installations.

A collection of morse telegraph and radio items

The _Icom IC-705_ portable operation power supply guide details the use of a car battery jump starter and a step-up/down converter for field power. It examines various power supply types, including LiFePO4 batteries, lead-acid batteries, and supercapacitors, discussing their respective advantages and disadvantages for QRP and portable setups. The resource emphasizes practical considerations such as capacity, weight, discharge rates, and charging methods crucial for reliable off-grid operation. The article compares the energy density and cycle life of different battery chemistries, noting that LiFePO4 batteries offer significantly more cycles (e.g., **2000-5000 cycles**) compared to lead-acid batteries (e.g., **300-500 cycles**). It also touches upon the integration of solar panels for recharging and the importance of proper voltage regulation to protect sensitive radio equipment, providing insights into maximizing operational time during DXpeditions or POTA activations.

Single-sideband (SSB) radio enhances spectral efficiency but poses challenges with audio intelligibility, particularly in noisy conditions. A microphone audio compressor addresses these issues by dynamically managing the audio signal’s dynamic range. It amplifies quiet sounds and attenuates loud ones, ensuring consistent audio levels for improved clarity. Benefits include increased intelligibility, higher average power, and reduced spurious emissions. While essential for optimal SSB performance, careful parameter adjustment is crucial to balance natural sound quality and effective communication across various operating modes.

A free educational website offering hands-on battery information. The tutorials evaluate the advantages and limitations of diverse battery chemistries, advise on best choices, and suggest ways to extend life.

Elektrodump.nl is an online shop from the Netherlands specializing in amateur radio products. It offers a wide range of categories including antenna masts, antennas, tuners, coax connectors, and cables. The site also features broadcast equipment, electron tubes, semiconductors, and various electronic components like capacitors and resistors. Additionally, it provides measuring equipment, power supplies, and transmitters, catering to both hobbyists and professionals in the field of radio electronics.

The article explores the concepts of return loss, VSWR, and S11 within the context of microwave engineering, highlighting the confusion arising from their definitions. It clarifies that these parameters, while seemingly distinct, fundamentally describe the same phenomenon related to wave reflection and transmission in microwave circuits. The discussion emphasizes the historical context and mathematical relationships among these terms, revealing that their interpretation can vary significantly across different engineering disciplines. Ultimately, it advocates for a pragmatic approach to using these parameters based on familiarity rather than strict definitions.

Off Grid Ham discusses the benefits of mobile ham radio operation in addition to fixed or semi-fixed base stations. The article highlights the challenges of antenna placement on vehicles, emphasizing the importance of a good ground plane for optimal performance. Tradeoffs between performance and appearance are inevitable, especially with modern vehicles that have plastic body panels. Bonding the coax shield to the car frame is often necessary to establish a good ground plane. Mobile ham radio operation is a valuable option that fills in the gaps left by fixed stations, offering flexibility and convenience for hams on the go.

Tubes are a dying technology. All modern transmitters, even high power ones, do work with transistors and other semiconductors. But many fondly remember their first homebrew transmitter and its hard to forget warm glow of a vacuum tube. The Station QRP website is especially for you to come into touch with tube technology. This site is all about handcrafted QRP AM tube transmitters.