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MT-Hell software for 16 bit Soundblaster cards. Sends seven parallel tones with careful dot shaping for minimum interference, and transmits a very nice sound by G3PPT

How to reduce and eliminate the RF interference at VHF caused by the wired network

The CAT and audio interface version 3 project by PA5CA presents a comprehensive solution for integrating amateur radio transceivers with computer sound cards, facilitating digital mode operation and CAT control. It includes detailed schematics for the interface circuitry, illustrating the isolation transformers for audio paths and optocouplers for CAT data lines, ensuring robust electrical separation between radio and PC. The resource also provides PCB layouts, enabling constructors to fabricate their own boards for this specific design. The project outlines the component selection and assembly process, emphasizing the use of readily available parts to build a reliable interface. It addresses common challenges in sound card interfacing, such as ground loops and RF interference, through its isolated design. This construction guide offers practical insights into building a functional interface, making it suitable for hams interested in DIY radio accessories for digital modes like FT8, RTTY, and PSK31.

A workaround to common RF interference on Samsung TV LED causing several issues like changing channel, swithcing to demo mode, or changing volume.

Simple steps you can take to solve most problems caused by station equipment

Solving interference from television channel 11 on 144MHz transverters by Chris Cox, NØUK, G4JEC

MFSK is an easy-to-use chat mode for real-time amateur contacts, nets and bulletin transmissions, but not intended for contesting or Bulletin Board System (BBS) use. It is a half-duplex non-Automatic Repeat ReQuest (ARQ) forward-error-correcting (FEC) mode. It performs well on long-path fading conditions and in the presence of interference

MorseExpert 1.15 decodes Morse Code audio to text, leveraging algorithms from CW Skimmer for optimal performance on weak, fading signals amidst interference on amateur radio bands. It processes audio from the device's built-in microphone or an external radio receiver via cable, optionally highlighting Ham callsigns and keywords. The application features a waterfall display with a bandwidth of 200-1200 Hz, decodes frequencies between 300-1100 Hz, and supports keying speeds from 12-45 WPM with automatic CW pitch detection. Recent updates include support for Android 15, edge-to-edge mode, improved stability, and a pause decoding button. A premium version offers an ad-free experience and user-selected text colors. Users can switch between General Text mode and Ham Radio QSO mode, which enhances word segmentation and highlights callsigns. The app also includes a frequency lock mode, text selection capabilities for copying, sharing, or saving decoded text, and provides guidance on reducing acoustic echo and constructing an audio attenuator for optimal radio interfacing.

A cavity filter, often a critical component in _duplexer_ designs, functions as a sharply tuned resonant circuit, allowing only specific frequencies to pass while attenuating others. These filters are essential for maintaining signal integrity in environments where multiple transmitters and receivers operate simultaneously on closely spaced frequencies, such as in repeater stations. The article details how these filters, sometimes referred to as _notch filters_, achieve high Q factors, which are crucial for their performance. Understanding the principles of cavity filters is fundamental for any amateur radio operator involved in repeater operation or designing custom RF front-ends. The discussion covers the basic circuitry and operational characteristics that enable these devices to provide significant isolation, often achieving **-80 dB** or more between transmit and receive paths. This level of isolation is vital for preventing receiver desensitization and intermodulation distortion. Properly tuned cavity filters ensure that a repeater can transmit and receive simultaneously on different frequencies without self-interference, a common challenge in VHF/UHF operations.

Amateur radio repeaters extend communication range for mobile and remote stations by retransmitting signals on a different frequency, often for emergency communications. The resource details various repeater bands, noting that 2 meters and 70 cm are primary for activity, with 10-meter repeaters offering potential national and overseas coverage. It specifies **18 channels** on 6 meters and **31 channels** on 2 meters, along with a new 70 cm offset of _7 MHz_ adopted in 2015. The content explains how repeaters can be linked via dedicated transmitters/receivers, landlines, or Internet VoIP systems like _IRLP_ and Echolink, enabling global connections. It also describes simplex gateways for multi-band operation and the use of CTCSS subaudible tones for access control and interference mitigation. The document highlights specialized repeaters for modes beyond voice, such as SSTV and ATV, particularly on 70cm and higher bands. Operational guidelines for efficient and courteous repeater use are referenced, along with links to Australian repeater listings and band plans.

The VU2BBB repeater, located in Matheran, Maharashtra, commenced operations in the late 1980s, a significant undertaking by the Bombay Repeater Society. This repeater facilitates VHF and UHF communications for local amateur radio operators, providing extended range and improved signal reliability across challenging terrain. Its establishment marked a key development in regional amateur radio infrastructure, offering a crucial node for local nets and general QSO traffic. The repeater's operational parameters include specific input and output frequencies within the 2-meter band, typically utilizing a standard offset. CTCSS tones are often employed to mitigate interference and ensure selective access for authorized users, a common practice for repeaters in densely populated areas. Regular maintenance and upgrades ensure _VU2BBB_ remains a reliable asset for the amateur community, supporting emergency communications and daily amateur radio activities. The _Bombay Repeater Society_ continues to oversee its operation, reflecting a sustained commitment to local ham radio services.

Building an amateur station for competitive radiosport involves a number of critical steps, regardless of the band or bands you focus on. These include, but are certainly not limited to: Station layout, Equipment interconnection and switching, Inter-station interference, Antenna selection. Radio interface with the logging program, CW and voice keyer integration, Rotator control

Can Home Solar Power and Ham Radio Coexist? It is possible, with minimal interference from the solar power system, provided you make some modifications.

Nearly half of all reception problems are due to deficiencies or faults in the television receiver, the aerial lead or the aerial. This article will help you to check whether the problem you are having is due to one of these causes.

Sixty-meter repeaters typically use a 1 MHz frequency separation between input and output, while 2-meter repeaters commonly employ a **600 kHz** split and 70-centimeter repeaters use a **5 MHz** offset. This article details the fundamental technical principles of amateur voice repeaters, explaining how they extend VHF/UHF communication range by receiving on one frequency and simultaneously retransmitting on another. It covers essential components such as receivers, transmitters, filters, and antennas, often situated on elevated locations for optimal coverage. The resource delves into the critical challenge of _desensing_—where the repeater's strong transmit signal overpowers its own receiver—and the engineering solutions employed, including antenna separation and the use of high-Q cavity filters. It also explores various control and timing systems, from basic squelch activation to more sophisticated microcontroller-based boards that manage functions like voice identification, time-out timers, and fault protection. Different access methods are discussed, including open access, toneburst, CTCSS subtone, and DTMF, each offering distinct advantages for managing repeater usage and mitigating interference. Furthermore, the article examines repeater linking, both conventional RF methods and modern internet-based solutions, highlighting how linking expands coverage and promotes activity across multiple repeaters or bands. It introduces less common repeater types such as 'parrot' repeaters, which use a single frequency and digital voice recording, and linear translators, capable of relaying multiple signals and modes simultaneously across different bands, often found in amateur satellites.

AmTOR may be considered as the next development from RTTY. AmTOR was introduced to overcome the problems with RTTY. As a result of its performance, it has become popular on the HF bands because it gives more reliable communication, especially when interference is present. It achieves this by using a coding system that allows errors to be detected and corrected.

The Japan Amateur Radio League (JARL) is cautiously watching new developments concerning the commercialization of Power Line Communications (PLC), while continuing to carry out joint experiments with a high speed power line communication promoters' alliance to reduce potential interference to radio communications.

Modem Telephone Super Filters For HF and AM Radio Interference.

Blog post announcing that Ham Radio, shortwave listeners and broadcast band listeners will be protected by Law in Europe

Article on radio frequency interferences, with a long list of common RFI cause, like Plasma TV, Solar panels inverters, fluorescent tube lamps.

Transmitting operations in the 50-54 MHz range offer some unique problems that over the past 50 years have stymied station owners, forcing them to tolerate quiet hours and hostility from family and neighbors attempting to enjoy other electronic services.

Ham radio transmissions can interfere with television reception. This is called television interference, or ham radio TVI. Consumer adoption of cable television has significantly reduced ham radio TVI. But the introduction of IPTV, or television over phone systems, has brought ham radio TVI back, often with a vengeance. Here's why

Our ideas about HF baluns have changed dramatically in recent years. The focus today is very much on suppressing unwanted common-mode RF currents, to reduce both the received noise levels and the risks of causing interference on transmit.

This article aims to help promote the proper configuration for having a clean signal on the waterfall to avoid interference to other users and also to vastly increase the effectiveness of your signal.

Effective operation of amateur radio repeaters, particularly in high-density areas, relies on coordinated frequency assignments to prevent interference. This resource from the _Illinois Repeater Association_ (IRA) serves as the official frequency coordination body for the state of Illinois, providing essential information for repeater owners and users. It details coordination policies, guidelines, and application forms for new and existing repeaters, ensuring fair and consistent spectrum utilization. The site also includes a comprehensive band plan, last revised in 2006, and a selective access policy (PL/Squelch Plan) updated in 2015, which are critical for maintaining orderly operations. The IRA website offers various repeater directories, sortable by frequency, city, and region, including a dedicated section for digital systems. These directories are invaluable for hams traveling through Illinois or setting up new repeater projects, helping them identify available frequencies and coordinated systems. The resource also provides meeting minutes, newsletters, and links to other regional repeater councils, demonstrating its role in fostering inter-state coordination. This structured approach to frequency management helps ensure reliable communications and minimizes QRM across the state, supporting thousands of repeater contacts annually.

The BikeLoop antenna project details the construction of a double magnetic loop antenna optimized for VLF frequencies, specifically around 136 kHz. This innovative design incorporates two orthogonal loops, which significantly enhance reception capabilities. Key construction hints include utilizing lightweight bicycle rims for the antenna structure, making it easy to transport and set up in various locations. The document provides valuable mathematical and electrical insights into the antenna's performance, alongside practical reception tests conducted in the Italian Alps, showcasing its effectiveness in capturing various VLF signals, including Sferics and FSK transmissions. Proper setup is crucial for optimal performance. The project emphasizes the importance of grounding and avoiding interference from nearby electrical sources. The reception tests revealed the antenna's ability to capture a range of signals, demonstrating its practical application for enthusiasts interested in VLF reception and antenna experimentation. Overall, the BikeLoop serves as an excellent starting point for those looking to explore the world of VLF frequencies and enhance their antenna-building skills.

When operating contest in a multi transceiver environment interferences between the 40m and 20m are guaranteed. An easy and inexpensive way to reduce interferences is to add coax stub filters

The areas noted in the forecast have the necessary atmospheric conditions to produce tropospheric bending of VHF, UHF and/or microwave radio waves. Tropospheric bending extends the range of radio & TV stations well beyond their normal limit and thus increases interference amongst stations as well.

DOMINO DF is a sensitive mode which, due to its incremental frequency keying and thanks to its interleaved multiple tones sets, is easy to tune and is few sensitive to interference and ionospheric effects. Domino faeture a great signal to noise ratio.

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

The Icom IC-7300 is a popular SDR transceiver known for its excellent performance in ham bands. However, users have reported issues with reception reliability outside these bands due to ADC aliasing. This phenomenon occurs when the sampling rate of the radio interacts with frequencies outside the intended range, leading to unwanted signals being received. For instance, when tuned between 30 to 36 MHz, users may inadvertently pick up WFM broadcast signals or PMR communications due to aliasing effects. This guide outlines modifications to improve the IC-7300's performance by addressing the low-pass filter design, which is crucial for reducing interference from these unwanted signals. The proposed modifications involve adjusting the low-pass filter on the PA unit to better attenuate frequencies that cause aliasing. Measurements indicate that the original filter design allows significant signal leakage, leading to false receptions. By implementing the suggested changes, users can achieve a notable reduction in unwanted signals, enhancing the overall functionality of the IC-7300. While the modification requires careful soldering, the benefits in performance make it a worthwhile endeavor for serious operators looking to optimize their SDR experience.

Mitigating impulse-type noise, a common challenge in the **HF radio spectrum**, often requires specialized processing before the signal reaches the transceiver's receiver stages. The NR-1 addresses this by functioning as an RF interference removal device, specifically a noise blanker, targeting transient noise sources. Its operational range extends from 1.6 MHz to beyond 70 MHz, making it suitable for various amateur radio bands and general shortwave listening applications. Unlike QRM eliminators or X-phasers, the NR-1 does not require a separate noise antenna for its operation, simplifying its integration into existing station setups. The device's design focuses on wideband performance, allowing its use both within and outside the allocated amateur radio frequencies. Documentation detailing its operation is available, providing insights into its technical specifications and deployment. This unit is a hardware product, conceptualized and implemented by SV3ORA.

Ban Power Line Technology a website devoted to defend amaterur radio against power line communications devices interferences

Operating in antenna-restricted communities presents unique challenges for amateur radio operators, often necessitating creative solutions for antenna deployment. This resource details the design and implementation of stealth antennas within a townhouse community in Exton, PA, where external antennas were strictly forbidden by covenants. The author, WB5NHL, describes his setup, which involved locating the shack in the basement and utilizing an unused space under the roofline of a finished third-floor loft for antenna placement. The content specifically addresses the practicalities of routing coax cables three floors and maximizing antenna performance within limited attic space. It covers solutions for multi-band operation, including dedicated sections for 40-10 meter and 80-meter antennas, along with strategies for mitigating potential interference issues. The approach emphasizes full compliance with community covenants, achieving maximum height-above-ground for horizontal antennas, enabling instant band switching, and efficiently utilizing available attic volume. While acknowledging limitations such as potential interference with high power and fixed antenna patterns, the resource provides a detailed account of a functional compromise for restricted environments. Links to individual pages on _coax cables_, _40-10 meter antennas_, _80-meter antennas_, and _interference issues_ offer deeper dives into each specific aspect of the installation.

The Intercontinental Amateur Traffic Net (Intercon) operates daily on 14.300 MHz, providing a platform for emergency communications and facilitating third-party traffic among amateur radio operators. Established in 1960, the net aims to foster goodwill and friendly relations within the ham community. It operates from 0700 to 1200 Eastern Time, with a focus on monitoring emergency traffic while encouraging operators to maintain a distance of at least 5 kHz to avoid interference. All licensed General Class operators and above are welcome to check in, using standard phonetics for clarity. The net features rotating Net Control Station (NCS) operators every hour, ensuring a diverse range of voices and experiences. Operators are encouraged to provide relays and assist with emergency traffic when necessary. While there is currently no membership for non-NCS operators, opportunities exist for those interested in becoming NCS operators. The net emphasizes professionalism and courtesy, making it a valuable resource for both emergency communications and casual check-ins.

Utilizing snap-on ferrite cores and practical insights, the author enhances their shack's cleanliness against electromagnetic interference. With meticulous experimentation and installation, they improve noise levels across HF bands, reflecting on the effectiveness of their filter in minimizing common-mode disturbances. Updates underscore ongoing refinement and cautionary advice for optimal filtering and radio reception amid changing RF environments.

The video delves into the significance of interference reduction in ham radio setups by utilizing ferrite materials. It demonstrates the use of spectrum analyzers and tracking generators to showcase the performance of ferrite devices in minimizing noise levels. The analysis includes insights on resistance levels, attenuation factors, and the impact of using multiple ferrite clamps or rings to enhance noise reduction capabilities. Viewers gain a deeper understanding of ferrite composition, characteristic curves, and winding techniques for effective noise attenuation in different frequency ranges. Overall, the video serves as a comprehensive guide to optimizing interference reduction in radio environments through the strategic use of ferrite materials.

If your multiple transceiver station is suffering of intrastation interference, this handy and inexpensive band pass filters and help you. QST article Sept 1988

This project details the creation of a portable GoBox housing an IC705, Windows 11 PC, and Bluetooth microphone. The robust setup, enclosed in a weatherproof Hofbauer Explorer Case, ensures stability and functionality for QRP and emergency radio activities. The aluminum-mounted devices minimize RF interference, and a built-in LifePO4 battery powers the 10.1 TFT touch LED monitor, providing approximately 12 hours of use in receive mode. With a focus on grab-and-go versatility, this GoBox stands as an efficient solution for outdoor ham radio operations.

This article clarifies the roles of baluns, ununs, common mode chokes, line isolators, and impedance transformers in amateur radio. A balun decouples balanced antennas from unbalanced feed lines, preventing interference. Ununs serve a similar purpose for asymmetrical antennas. Common mode chokes and line isolators suppress common mode currents, reducing noise. Impedance transformers adjust antenna impedance to match feed lines but do not decouple or suppress common mode currents. Understanding these components is crucial for optimizing antenna performance and minimizing interference.

If you are having problems with RFI from Solar Panels this document from QST provides useful advice. According to this article it is possible to prevent and mitigate RF interferences, with your amateur radio equipment, by suppressing the RF either in the shack and to the solar power infrastructure.

Learn how to improve reception on the hf bands by setting up a noise cancelling system that nulls out local interference. This article describes a system using a 'Main Station Antenna' to receive a wanted signal and associated QRM, and an 'Auxiliary Antenna' to pick up unwanted interference. Gain and phasing controls are used to reduce/remove interference, leaving only the wanted signal. Tips are provided based on the author's personal experience, applicable to commercial noise cancelling products, kit form, or homebrew setups. Discover the importance of configuring the 'Auxiliary Antenna' to optimize your system and improve readability of wanted stations.

Antenna patterns are all about interference. Presentation on wire antennas for HF bands. Dipoles, horizontal and vertical dipoles, effects of ground on radiation patterns, multi-band wires antennas. Knowing what you should expect from the radiation patterns for waves on your wires will help you choose what will work best for your needs. The principles of interference can lend insight into what to expect from a wire antenna.

Radio Frequency Interference (RFI) has always been a source of concern for the Radio Amateur. Until the recent introduction of complex circuitry in the home, our communications gear has been the main source of potential RFI. In this computerized age of ours, increasingly complex and sensitive receivers are being barraged by these and other sources of RFI.

This article addresses the issue of unwanted RF in amateur radio setups and introduces a practical method to measure common-mode currents (CMC) using a homebuilt RF meter. The meter, constructed with readily available materials, measures unwanted RF on the coaxial cable shield by inductively coupling to the shield using a split-bead ferrite. The article provides detailed instructions on building the meter, interpreting measurements, and using ferrite chokes to mitigate RF interference. Emphasis is placed on the importance of verifying CMC levels and installing chokes to improve equipment performance.

Online interactive elevationmap can help radio amateurs by predicting signal propagation, optimizing antenna placement, planning coverage, ensuring line-of-sight, mitigating interference, and enhancing emergency communication. T

Putting one of those old modems back into use.AMTOR is an acronym for AMateur Teleprinting Over Radio and was mostly used on HF. The mode is based on the marine SITOR code that was introduced to amateur radio by Peter, G3PLX. The mode is an enhancement of RTTY with active error correction that copes reasonably well with interference and fading.

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

Chokes and isolation transformers are essential for receiving antennas to mitigate common mode current, which induces noise and interferes with signal quality. Common mode chokes, formed by winding feedline through ferrite cores, block unwanted current effectively. Proper selection of core material and winding turns ensures resonance near the operating frequency, reducing interference. Isolation transformers further minimize interference, crucial for multi-transmitter stations.

This document outlines the construction of a homebrew Buddipole antenna variant, designed for portable use and emergency services. The antenna utilizes telescoping whips and loading coils, enhancing its versatility across various HF bands. Key components include fiberglass rods, brass fittings, and Anderson Power Pole connectors, ensuring robust electrical connections. The design emphasizes non-inductive materials to minimize interference, while practical assembly techniques, such as epoxy and heat shrink tubing, are employed for durability. This variant aims to improve upon traditional Buddipole designs, offering greater strength and functionality.