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A multi-mode PC to radio interface for PSK, CW, Packet and more digital modes.

A post about the construction and measurements of a Resonant Feedline Dipole cut for the 10M band

Sensitive RF probe based on the use of a superbright LED by G4TKV

Win EA6DDlog is a freeware logging application for Windows, developed by EA6DD Biel. It integrates features from existing software like Swislog, Urelib, Logger, and HamRadio Deluxe, presenting a Multi-Document Interface (MDI) similar to Logger. The program prioritizes simplicity, practicality, and operational speed, allowing functionality even on less powerful PCs. It does not require a formal installation; users can run it directly from a portable drive or any directory. This logging utility supports CAT control through Omnirig by Alex Shovkoplyas, VE3NEA, which is automatically installed if not already present on the system. It also offers QSL printing capabilities and connections to online callbook services such as QRZ and HamQTH for contact information. EA6DDlog includes an automatic update mechanism that checks for new versions upon startup, requiring internet access. For Windows Vista users, disabling User Account Control (UAC) is recommended for proper update functionality. The software is part of a broader development effort aiming for cross-platform compatibility, with future versions planned for Windows Mobile, Linux, and macOS.

CAT (Computer Aided Tuning) connects computers with ham radio. Yaesu FT-890 intercace and ICOM IC-Q7 schematics by DK7IN

Radio Frequency Interference To/From touch lamps and dimmers

Notes about generating RF sweep signals on the Arduino for filter testing, a digital version of the old Wobbulator concept

Recordings of RF noise from personal computers, peripherals and related equipment. If you can match noise at your location to one of these files then you can be confident that you know where your noise is coming from.

Operating magnetic loop antennas requires careful consideration of RF safety, particularly regarding near-field magnetic field intensity. This resource presents calculations for magnetic field strength (H-field) at various distances from a magnetic loop, emphasizing that the H-field is significantly higher than the E-field in the near-field region due to the inductive nature of the radiating element. It provides specific formulas and examples for determining safe operating distances based on power levels and loop dimensions, crucial for compliance with RF exposure limits. The analysis compares calculated H-field values against FCC and ICNIRP maximum permissible exposure (MPE) limits for controlled and uncontrolled environments. It demonstrates that even at QRP power levels (e.g., 5W), the H-field can exceed MPE limits within a few feet of the antenna, necessitating greater separation distances than often assumed for electric field considerations. The practical application of these calculations helps amateur radio operators configure their stations to ensure personnel safety and regulatory compliance when deploying compact, high-Q magnetic loop antennas.

May 2015 Radcom Article on common-mode chokes that can be used for control cables, phone lines, but mostly on typical HF antenna systems. This article explain what common mode chokes does, why you meay need one, properties common mode chokes should have, how to build and measure performances.

The use of dummy load is mandatory for off-air adjustment of the transmitters. Build one.

Over 45 years of dedicated work by Robert Sherwood, NC0B, culminated in a wealth of technical insights, particularly concerning **receiver performance** and the intricacies of transceiver design. The site provides access to numerous presentations from events like Dayton Contest University and W4DXCC, covering topics such as optimizing rig performance, the evolution of lab testing, and the impact of roofing filters on transmitted IMD and receiver characteristics. These resources offer detailed analyses and practical advice for serious operators and contesters. While product manufacturing, including the SE-3 MK IV synchronous detector and various Drake R-4C accessories like roofing filters and cooling kits, has ceased, the legacy of technical documentation remains. The site details specific products like the Icom IC-781 and R-9000, and offers insights into 455 kHz mechanical and crystal filters, along with DSP protection strategies. Crucially, the site features extensive receiver test data, allowing radio amateurs to compare the performance of various transceivers. This data, often presented in white papers and slide shows, includes detailed measurements and explanations of key performance metrics, serving as a valuable reference for understanding and selecting high-performance HF gear.

A simple PSK31/digital interface which can connect your transceiver to a PC soundcard for digital modes.

This circuit came out of some work done for two antenna analysers

A cheap rf signal generator for 2.4 GHz

A amateur radio guide to RFI, ferrites, baluns, and audio interfacing by K9YC

Chesterfield Islands DXpedition 2000

This page is to provide links to resources and information regarding technologies to reduce computer interference

Tri-Cities Frequencies, Live Scanners, CTCSS information and more

This is a concept paper, not a constuction article. There are too many variables to propose a one size fits all design. However, this paper should give you the basic idea how to do it

Homebrew your PC sound card to radio interface with this circuit obtained from the pages of Ernie Mills WM2U.

This article describes a generalised unit for interfacing a transceiver's TTL/CMOS interface to RS-232.

Building a Resonant Feed line Dipole for 2 Meters

Pictures and description of a homemade 1.3 GHz and 2.4 GHz RF Signal Source

The function of the XPhase is based on the fact that the interfering signal, received by an auxiliary antenna, is added phase-shifted to the signal received from the main antenna. When the phase-shift is more or less 180°, the interfering signal is canceled out.

Trained amateur radio communicators under ARES, RACES and Skywarn serving Harford County, Maryland communities

Discussion of some design features that would be present in a perfect, or near-perfect, amplifier.

This article describes the details of the design, which can be easily scaled for just about any HF band. The antenna described in this article is for the 20 meters band.

Demonstrates a range of specialized radio frequency equipment and consulting services for amateur and professional applications. The offerings include _Vector-Finder_ direction finding antennas, various test equipment such as _gate dip meters_ and RF sniffers, and communications receiving adjuncts. Additionally, the company produces satellite antennas for weather satellite reception, voice amplification devices like the _Flex-Mike_, and custom prototype circuit boards. The company's product line addresses needs for precise RF measurement, signal detection, and specialized antenna systems, particularly for direction finding and satellite communications. Their historical association with National Radio (HRO) suggests a legacy in radio technology. The site also highlights a subsidiary, Sierra Mountain Products, which offers outdoor recreational gear, indicating a diversification beyond core RF manufacturing.

MicroSignals produces a line of RF and IF signal processing components that offer high performance at an exceptional value. To achieve this MicroSignals began with an engineering team that possessed an excellent background in RF Transformer and Balun design.

Practival project that contains two isolation transformers, one for AF from the tranciever to the line in on a soundcard, and one from the audio out of the soundcard back to the mic / data input of the radio. Both of which are variable inside the interface via two preset resistors.

This test circuit is easy to duplicate, and demonstrates the extreme voltages that appear in an amplifier when the load is improper for the amount of drive power applied.

CAT and Digital modes interface for the Yaesu FT-817

Introduction to the use of clusters and Packet Radio, hardware, settings and commands by ON4SKY

Radio Free Europe / Radio Liberty is an international news and broadcast organization serving Central and Eastern Europe, the Caucasus, Central Asia, Russia, the Middle East and Balkan countries.

An home made low pass filter for 70 MHz by IK0VAQ

RFI Forum at eHam.net

Experiences with the end-fed dipole based on the concepts presented by J. Taylor in an article titled RFD-1 and RFD-2: Resonant Feed-Line Dipoles in QST. August 1991.

Installing mobile radios in your new megabucks car can be a frightening proposition - especially if RF from your rig could damage your shiny new roadster

A simple RF sweep generator circuit diagram by JF1OZL

This project is an interface box for the Yaesu FT-817 that includes a band output port, a computer serial interface, and a remote interface for the FL-7000 solid state power amplifiers.

Cushcraft A3S performances with the A743 kit to add 30 and 40 meters

This project was intended to accompany the stealth antenna project. Author want to see how effective a noise canceller could be in reducing the background noise floor when attic / stealth antennas are being used.

With the bluecat interface it is possibile to connect a Yaesu FT 817 857 897 to a computer or a android smartphone without any cable or interface, using a bluetooth wireless connection

The only worldwide amateur radio repeater directory. Supports Android, iPhone, web, RT Systems, CHIRP GPS enabled. AvMap, Garmin, TomTom

The author who works successfully via EME on this band wants to describe his own yagi design and give some of hints for the construction. by Heinrich F. Reckemeyer, DJ9YW

Using Andrew FSJ1-50A 1/4" Superflex Heliax with PL-259 Connectors

This circuit will let you look at the signal and frequency output of your transceiver.

Understanding and eliminating RF Interferences caused by your home devices

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.