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The Sharpie Probe, homemade with simple tools and few resistors

Article showing how I've made a mains filter to reduce EMC in the electricity supplying my shack. I've used a type 31 Fair-Rite ferrite core and the video shows how this performs on 160m through to 40m.

Blackford and surrounding counties Police, Fire, EMS, and EMA.

Solving Ignition Noise RFI article. Help on removing noise interfences caused by ignition

Audio files to help identify rf noise (rfi). Identify the RFI that interferes with your reception. RFI Noise identification.

Sound Card Interfacing for RTTY, PSK31, and SSTV

How track and solve electrical interference from you computer

The Elecraft K2 transceiver requires specific modifications for optimal soundcard digital mode operation, particularly for PSK31. The original article, circa 2001, details initial challenges with manual PTT and speech compression settings. A key modification involves adding headphone audio and a compression disable signal to the K2's microphone jack, utilizing pins 4 and 5. The **COMP0** signal, active low, is shorted to ground via a non-inverting open collector switch circuit, comprising two resistors and two transistors, mounted on the SSB board near U3. This circuit provides effective control of an analog signal line with good noise immunity. The switchbox itself repurposes a computer COM port switch, using only two of its original connectors and four of the nine poles. It integrates a microphone preamplifier, a PTT circuit built with 'flying leads' construction, and RCA jacks for soundcard connections. A trimpot adjusts the audio drive to the K2. The central DB9 connector links to the K2's mic connector via a shielded RS232 serial cable, ensuring proper grounding and signal routing. An external footswitch PTT jack is also included. Further enhancements include a **noise-canceling microphone** preamp based on a QST December 2000 article, adapted for Heil mic elements. This preamp, built with pseudo-Manhattan style construction, provides a gain of approximately 2 by changing emitter resistors (R9 and R16) from 680 ohms to 330 ohms. A 10-ohm series resistor and 47 µF capacitor on the +5V supply mitigate noise spikes.

This voice-keyer-interface connects between a Yaesu FT1000MP and a PC's sound card & COM port. It can be used as a voice-keyer with Contest Voice Blaster and as a voice-keyer and CW-keyer with Writelog.

The intrepid newcomer encounters common mode problems in a mobile environment. Implementing some common mode chokes will be possible to reduce interferences

This resource details the four primary functions of a ground system: lightning energy dispersion, equipment safety, RF return path provision for end-fed antennas, and management of induced RF currents. It clarifies that a ground system's effectiveness varies depending on its specific function, noting that a good lightning ground might not be an effective RF ground. The content emphasizes that proper antenna system design, including baluns and appropriate feedline lengths, often negates the need for an RF station ground to mitigate common mode currents or RFI in the shack. The article quantifies lightning energy, stating its peak is in the dozens or hundreds of kilohertz, with damaging energy extending to hundreds of megahertz, and currents reaching thousands of amperes. It recommends solid, wide, smooth copper surfaces for ground leads to achieve low impedance across a wide frequency range. The author, W8JI, shares practical insights from his station, which includes two 300-ft towers and four 130-ft wire verticals, detailing his use of common point grounds and _DX Engineering RR-8 HD_ antenna switches for lightning protection without coaxial surge protectors. Specific examples of antenna systems prone to common mode current problems are listed, such as random wire antennas without proper feedline lengths and off-center fed dipoles. The text also explains how a ground screen or radial system can reduce local noise sensitivity for vertically polarized antennas by covering the lossy earth.

The Yaesu FT-1000MP Mark-V, introduced at Dayton 2000 Hamvention, features a higher RF power of **200 W PEP** and a Class-A amplification SSB mode at 75 W. Key enhancements include an _Interlocked Digital/Analog Bandwidth Tracking system (IDBT)_, a Variable Front-End Filter (VRF) preselector, and improved ergonomics, notably a multi-function shuttle jog dial. This model, a successor to the 1996 FT-1000 and FT-1000MP, was designed to compete with high-end transceivers, despite its retail price of $4200 initially. The transceiver's physical dimensions are 406 x 135 x 348 mm (16 x 5.3 x 13.7 inches) with a weight of 14 kg (31 lbs), making it substantial. Its rear panel offers over 20 connections, including power, external DSP speaker, BAND DATA I/O, ALC, and multiple interface jacks for DVS-2, Packet, and RTTY. The unit also provides two keyer inputs, a DB9M serial interface for CAT, and two PL female antenna connectors, plus additional receive antenna jacks. Despite its advanced internal architecture, including two independent receivers with their own IF filters and AGC loops, the display technology, utilizing fluorescent discharge rather than LCD, contributes to an older aesthetic. The control panel is extensive, featuring 92 knobs and buttons, alongside numerous LED indicators for various modes and functions.

ATV 432 MHz AM transmitter schematic

The Kenwood TS-570D(G) transceiver (I), by Thierry Lombry, ON4SKY

A full galvanic isolation interface for digital modes tested with FT-847

SS232K - The simple and safe RS232 interface for Kenwood radios

This is a prototype of the WA4DSY 56KB RF modem. It is intended for use on amateur packet radio networks. The modem generates RF in the 28 to 30 mhz range and requires and linear transverter to convert the signal to a UHF or microwave ham band

Demonstrates the construction of a custom programming cable for Yaesu VX-7R and VX-5R handheld transceivers, enabling computer interfacing for memory management and frequency coverage adjustments. The resource details a six-transistor circuit design, powered by the computer's RS232 interface, utilizing readily available and inexpensive discrete components. It includes a complete bill of materials, specifying transistors like the _2N2222_ and _2N3906_, diodes, and resistors, along with a matrix board layout for compact assembly within a 75x50x25mm enclosure. The guide provides practical tips for working with matrix board, such as scoring and snapping, track cleaning, and component soldering order. It outlines the specific connection requirements for both the VX-7R (via Yaesu's CT-91 breakout lead with a 2.5mm stereo jack) and the VX-5R (via CT-44 or a four-section jack), detailing signal and ground pinouts. The author successfully tested three circuits, documenting the one with complete two-way communication, allowing users to program their rigs with software like _VX-7 Commander_ and achieve capabilities beyond commercial cables, including band adjustments.

What become our QSL once sent ? QSL routes, IRC and green stamps, the best and worst practices.

High quality VHF/UHF Yagi (directional) antennas

Whith more than 20 years of ham practicen SWL Thierry LOMBRY, alias ONL5183, has written several technical pages about ham activities, including propagation, radio perturbations, radioastronomy, DXing, QSLing, ham-spirit, review of material and more. This very interesting website is completed by a large French section devoted to amateur astronomy illustrated with vivid colors pictures.

Special test lead that converts your regular DC voltmeter to a RF reading voltmeter

A 13 cm loop yagi antenna made from key rings

Learn how to start using ham radio satellites for your DX contacts, PDF presentation by Dave Long

Telephone EMI, questions and answers on how to solve interference problems to phone lines

Why all the mystery surrounding baluns ? To use or not to use baluns

based on an FT-1000MP Reflector discussion with Bill Heinzinger, W9OL, 15/16 November 2002

In his back office section, ON4SKY, initiates in a few articles the beginners in the art of QSLing and award chasing.

Software Defined Radio manufacturer, SDR-IQ NetSDR SDR-IP and IF-2000

Thierry Lombry, LX4SKY (aka ON4SKY) has developped a excellent educational website mainly devoted to amateur astronomy but it includes also a large section dealing with amateur radio activities includes several interesting pages about radio astronomy and SETI

A pdf file with drawings and instruction to properly assembly and solder most popular coax cable connectors

How to make an effective RF Choke. The coiled coax choke is the easiest to make but also the least effective. This article includes some general guidelines for winding coax chokes on a 10cm PVC pipe using RG-58 or RG-213 coax cable.

Schematic diagram of the VLA 200 power amplifier by RM Italy

A chart presenting the results of impedance measurements made on a variety of common-mode choke implementations across the frequency range 1MHz to 30MHz by G3TXQ

An improved version of DK9NL QRM Killer, with dedicated noise sampling antenna for completely filtering of plasma TV rattle on HF bands

Easy to build RS232 keying interface for FSK and CW. Works with most popular RTTY software like MMTTY. Also works for with most contest software such as N1MM and Writelog for CW keying. Uses the RS232 port RTS, DTR, or TX data, optically isolated, PC boards available.

Benelec Pty Ltd specializes in the design and manufacturing of **antennas** and RF components, covering a broad frequency range from 0.002 GHz to 8 GHz. Their product line includes Land Mobile Radio Antennas, such as HF 2-30MHz, VHF 40-180MHz, and UHF 200-520MHz models, alongside specialized Military Antennas for dismounted, UxS, C2, and EW applications. The company also produces Cellular Antennas, including 4G/5G and GPS/GNSS types, and Marine Antennas for both vessel-mounted and fixed-site installations. Additionally, Benelec offers a comprehensive range of coaxial cables, connectors like N-Type and SMA, and various radio accessories. The company's offerings extend to RF components such as duplexers, diplexers, and 50 Ohm loads, as well as DAS components like directional couplers and hybrid combiners. Benelec provides EMP and lightning protection solutions, including 1/4 Wave Stub protectors and replaceable GAS capsules. Their product catalog also features P25, DMR, and FM Analog radios, along with portable and mobile radio accessories like batteries, chargers, and cabled headsets. The company supports various sectors with robust communication solutions.

This article includes an online calculator for a 3 element Yagi Antenna. The formula and basics theory of Yagi Antenna are also explained with examples.

Thierry LOMBRY, ON4SKY, gives advice to amateurs about lightning protection of an hamshack, including pictures and links.

Performance chart of VHF antennas in a stacked array

Computer Control and Soundcard Interface for the Icom IC 706

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

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

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

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.

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.

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

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.

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.