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Mitigating RF noise in a mobile operating environment, particularly within a _Jeep TJ_ vehicle, presents unique challenges due to the vehicle's electrical system and chassis characteristics. This resource details practical methods for identifying and suppressing various forms of radio frequency interference (RFI) that can degrade receiver performance for both CB and amateur radio transceivers. It covers common noise sources such as ignition systems, alternators, fuel pumps, and computer modules, explaining how these components generate broadband or specific frequency noise that impacts radio communications. The guide offers actionable solutions, including proper grounding techniques, the strategic use of ferrite beads and toroids on power and data lines, and the installation of bypass capacitors. It discusses the effectiveness of different filtering strategies for DC power lines and antenna feedlines, illustrating how a clean power supply and shielded cabling can significantly reduce conducted and radiated noise. The information presented helps operators achieve a lower noise floor, improving signal-to-noise ratio and enabling clearer reception of weak signals, which is crucial for effective mobile DXing or local ragchewing.

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.

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.

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

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

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

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

Chesterfield Islands DXpedition 2000

Building a Resonant Feed line Dipole for 2 Meters

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

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

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

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

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

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.

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

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.

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.

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.

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.

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.

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

CAT and Digital modes interface for the Yaesu FT-817

An home made low pass filter for 70 MHz by IK0VAQ

A simple RF sweep generator circuit diagram by JF1OZL

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.

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

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.

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

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

Understanding and eliminating RF Interferences caused by your home devices

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.

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

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

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

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.

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

PTT and souncard interface for the kenwood TM255 and TM455

Excellent article and guide to choose the best RF power amplifier that fit your needs by ON4SKY

How to connect a mose key to a pc using the standard RS232 serial ports by F8EHO

Radio for Peace International (RFPI) is a Global Community Radio Station located in Costa Rica, Central America that broadcasts progressive news on shortwave radio and the internet on topics of Peace, Human Rights and the Environment. RFPI gives a voice to the voiceless by promoting democratic communication.

Auroral Large Imaging System, ALIS

Complete guide to receive weather satelite images with a RTL SDR dongle and free software

Home Brew a 4-1000A RF power amplifier project by W4NFR

The Megacycles combine the hobbies of amateur radio and bicycling. This group is not a club as there are no officers, dues or by-laws.