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Monitoring extremely weak signals in the QRSS (Very Slow Morse) mode requires specialized receiving and processing capabilities to extract information below the typical noise floor. This project provides a software solution, _QrssPiG_, designed to run on a Raspberry Pi, enabling it to function as a dedicated QRSS grabber. It interfaces with various Software Defined Radio (SDR) devices, including the popular _rtl-sdr_ dongles and _HackRF_ units, to acquire raw I/Q data streams. The software then performs the necessary signal processing to visualize and decode these faint, long-duration CW transmissions, often operating with milliwatts of power. The system leverages the computational power of the Raspberry Pi for real-time signal analysis, allowing hams to participate in QRSS experiments and monitor distant beacons. It supports different SDR hardware, offering flexibility in setup and deployment for home stations or remote monitoring sites. The project includes detailed instructions for installation and configuration, making it accessible for those familiar with Linux environments. This grabber is particularly useful for tracking propagation on the LF and HF bands where QRSS activity is common, providing a visual representation of signal presence over extended periods.

Measuring noise fiugre on the W2IMU horn and the dual-dipole-feed

Active antennas can be very useful, in particular they can help reduce local electrical noise by allowing the antenna to be installed in a corner of the garden well away from house wiring. The original PA0RDT antenna uses a very small patch for the antenna and relies on the antenna being installed quite high.

The resource, "Conventional Use of Transmission Line," meticulously details the operational principles of transmission lines, emphasizing the Transverse Electromagnetic (TEM) mode of energy transfer. It clarifies that for a line to function purely as a transmission line, all currents must be confined internally, with external fields ideally zero. The discussion differentiates between balanced and unbalanced lines, asserting that while both require equal and opposite currents within the conductors, the key distinction lies in the voltage relationship of each conductor to the surrounding environment. It highlights that a good antenna pattern does not inherently confirm proper feeder balance, and that common-mode currents can lead to RF in the shack and increased noise levels, even without pattern distortion. The article further explains that a transmission line can become a radiating conductor if energy is applied in a non-TEM mode, leading to common-mode issues. It cites classic texts like Jordan and Balmain's "_Electromagnetic Waves and Radiating Systems_" and Kraus's "_Antennas_" to support its definitions of TEM mode operation. The content also explores non-transmission line applications of parallel or concentric conductors, such as _coaxial dipoles_ and _folded dipoles_, which intentionally operate in non-TEM modes for antenna functionality. The author, _W8JI_, stresses that simply measuring equal currents is insufficient to confirm a balanced feeder; phase and voltage balance to ground are equally critical.

Radio Astronomy Supplies astronomy products since 1994 including radio telescopes, LNA's, noise callibration source, books, videos.

This article shows how to make a mains filter that can be extremely effective in reducing and in some cases eliminating completely EMC from the electricity supplying your shack

How to receive NOAA weather satellite with a home made QFH Antenna. This project includes some easy and efficient notch filters to suppress noise from FM frequencies

The Tri-pole antenna, a clever modification of a standard dipole, allows for dual-band operation by integrating a third element. This design effectively shortens the overall dipole length by 10 to 20 percent, simplifying antenna rotation and offering a compact footprint. KK4OBI's article delves into the operational principles, using a 6 and 10-meter Tri-pole as a primary example, and provides comprehensive instructions for constructing any Tri-pole antenna within the 6 to 15-meter range. Key to the Tri-pole's performance is its off-center feed, necessitating a common mode choke at the feed point for optimal tuning and reduced noise. The author outlines a methodical approach to determining element dimensions, starting with a vertical element frequency calculated as 0.47 times the sum of the desired upper and lower band frequencies. This calculation, along with K-values derived from trend lines, guides the initial lengths for the horizontal arms, demonstrating how a 10m-6m Tri-pole can achieve a total horizontal length 78% shorter than a conventional 10-meter dipole. Tuning and balancing are critical, with the article detailing adjustments to arm lengths and the vertical element to achieve balanced SWR values, as validated through 4NEC2 simulations. Radiation patterns are analyzed at various elevations, showing gains around 5.7 dBi and favorable take-off angles for DX contacts. Construction details specify aluminum tubing dimensions, U-bolts, and an SO-239 connector, emphasizing the importance of a ferrite-based choke for wideband operation.

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.

If your 756 has lots of noise with crackles and sweeping heterodynes, especially noticeable on AM, it may be due to a faulty electrolytic capacitor in the noise-blanker circuit

Clarifies the intricate process of calibrating the _Elecraft K2_ dial, addressing common user challenges and lively discussions on the Elecraft reflector. Wilhelm, W3FPR, dissects the K2's PLL synthesizer design, chosen for its low phase noise, kit-friendly duplication, and cost-effective components. The resource emphasizes the critical role of the 4000.000 kHz reference oscillator's accuracy during CAL PLL, CAL FIL, and CAL FCTR functions, noting its dependence on temperature and crystal stability for optimal performance. Explaining the K2's frequency display, the document reveals it relies on microprocessor-driven look-up tables generated by CAL PLL for VFO values and CAL FIL for BFO values. In SSB and RTTY, these combine, while CW and CWr modes also factor in the sidetone pitch. The author details inherent limitations, such as the 10 Hz increment resolution of the dial and varying PLL step sizes—from 3 Hz on 160 meters to 10 Hz on 10 meters. BFO increments range from 20 to 35 Hz, collectively limiting practical dial accuracy to within **20 Hz** with diligent effort, or **30 Hz** for a slightly less demanding task. The guide outlines a four-step calibration procedure: setting the reference oscillator, running CAL PLL, running CAL FIL, and setting all BFOs. It highlights the _N6KR Method_ as a particularly easy and accurate approach, requiring only the K2 and a known frequency source like WWV for zero-beating, eliminating the need for external test equipment.

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.

Icom IC-7851/7800 LO C/N Characteristics Comparison

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.

This article discusses how volume reduction can help in the reception of weak signals by reducing the noise level. It is commonly known that reducing the volume also reduces the background noise, and especially in the reception of weak digital signals it can be beneficial

This is a very small vertical 160m antenna that fits in the loft of even my small house. It was built as a way of getting a signal out on 160m for local AM contacts, but the local noise level was far too high to allow it to be used at night for this purpose. However, on WSPR it did a pretty good job with WSPR spots from a very long way across Europe being received when running 2.5W out.

QRM.guru has been developed to assist radio hams in dealing with RF noise. This is an educational and reference resource.

This antenna is reported as being lower noise than conventional yagis and had a very low SWR for 500 KHz.

The Meteor-M N2 is a polar orbiting Russian weather satellite that was launched on July 8, 2014. Its main missions are weather forecasting, climate change monitoring, sea water monitoring/forecasting and space weather analysis/prediction. Meteor-M N2 transmits images using the digital LRPT protocol at around 137.1 MHz with can be received with an RTL-SDR.

HAM-made engineering products supplies and produces coaxial relays, antenna switches, sequencers, roller inductors, variable capacitors, low noise preamplifiers, RF power rotary switches and coil bodies.

An article about the Beverage antennas, super long wire receiving antennas thar are unidirectional and have a very low noise that makes this antenna excellent for low band dxing. By Thomas R. Sundstrom W2XQ, 73, June 1981, 73 Magazine

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.

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.

These pricey battery-powered devices are the only type of generator that can be used indoors safely. The article reviews pro and cons of power stations evaluating runtime, power delivery, power quality, ease of use, and noise.

Signal to Noise Ratio, definition and application to Radio Communications. Signal to Noise Ratio (SNR) is a figure of merit that compares the level of a desired signal to the level of background noise.

The 80-meter Skyloop antenna, a top-performing HF antenna, excels in weak signal work, low-noise operation, and omnidirectional coverage. Ideal for fixed stations, it delivers strong performance at low power, outperforming many alternatives, including 80m half-wave end-fed antennas. Requiring significant space for deployment, it’s well-suited for NVIS and groundwave use. Though not portable, it’s cost-effective and durable, with minor maintenance needs. Tuning may require adjustments for optimal resonance. It’s a standout for base stations, though a lighter portable version could enhance its versatility.

Common-mode chokes are useful solutions for RFI reduction. Winding a few turns of coaxial cable on the FT 240-31 toroid can reduced the noise below the received noise floor. In this article author measure different chokes

How to solve the problems with the ICOM IC R7100 receiver that every time the squelch opens or closes, it produces a clicking noise.

2m 70cm 23cm Low noise Amplifiers, 3 Low noise amplifiers Outdoor unit with DB6NT parts completed.

Repairing an Anritsu MS2711A handheld spectrum analyzer

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.

Hamradio_copilot is an open-source tool designed for DXers and contesters who need real-time situational awareness. It is ideal for operators who want to visualize propagation trends instantly rather than scrolling through raw text streams of cluster spots. Rally acting as a copilot for your station, this tool transforms raw data into actionable intelligence. By visualizing Signal-to-Noise Ratios (SNR) across different bands, it helps operators make quick decisions on which band to prioritize or where to point their antennas, effectively showing not just who is on air, but where the propagation is currently open from your location. This is a fantastic information for avid contesters. The software aggregates data from two primary services: - Reverse Beacon Network (RBN) via Telnet. - PSK Reporter via MQTT feeds. It processes this data to generate a comprehensive HTML report featuring SNR heatmaps and statistical breakdowns by ITU Zone. Users can filter data by specific zones or country codes (ADIF), analyze historic time ranges, and optionally integrate solar weather data. The complete source code is available on GitHub, allowing for community customization. It is written in Python and uses SQLite for data management.

WB8LZR details the construction and initial field results of a multi-band vertical wire antenna, designed to complement his existing horizontal loop for improved DX on 80 meters. The antenna utilizes a 67-foot vertical wire, configured as a quarter-wave radiator on 80m, and employs a 1:1 current balun for RF isolation on 80m, 30m, and 17m. For bands like 40m, 20m, and 10m, where the wire acts as a half-wave or full-wave radiator, an additional impedance transforming _unun_ is integrated to manage the significantly higher feedpoint impedance and voltage. The author notes the vertical's performance as a receiving antenna, observing reduced noise compared to his main horizontal loop, particularly on 80m, and even hearing some long-path signals the loop missed. Initial QRP contacts, including a **1-watt** QSO with a _VP2 station_ on 30m, demonstrate its transmit capability. While the radial system is currently rudimentary, the project outlines practical considerations for multi-band vertical deployment and impedance matching.

ICOM IC756 PRO II III, PS125 Fan Modifications, install an external cooling fan on the ICOM IC756 PROIII to minimize the heat on the chassis, then will perform a fan modification on the ICOM PS125 power supply to minimize the fan noise.

Replacing fan to the Elecraft K3 and solving temperature issues after replacement, by changing fans with other compatible ones.

Ribbit is a novel digital text messaging mode for VHF/UHF communications for recreational and emergency use which radically increases the density of information transmitted by spectrum used. It leverages the computing power of the modern smartphone to increase the capabilities of any Handy Talkie without requiring any additional hardware or cable. A Ribbit message is fixed in duration at 1250 milliseconds. It is sent over audio modulation with a 2kHz bandwidth centered on 1.5kHz. It is preceded by 400ms of white noise to open analog squelch circuits.

Amateur radio enthusiast Jean-Paul Suijs discusses combating manmade noise (QRM) in radio signals using AI. Detailing experiments with phase-shifting techniques and the self-learning nature of AI, he explores AI-based audio processing apps for real-time noise cancellation during radio contests, demonstrating results on both medium wave and shortwave bands.

Exploring digital radio modes, the author rethinks how to adjust transmit and receive levels in WSJT-X. Despite effective communication using Yaesu's settings, a new procedure aims for better performance. For RX, set audio device levels to 100%, disable AGC, and adjust RF gain. For TX, enable "Remember power settings" and adjust power output to avoid ALC engagement. This method ensures reliable communication without signal degradation, enhancing dynamic range and minimizing noise.

The document details the construction and performance of a rotatable flag antenna designed for a small lot. The 7x14 feet flag, built with fiberglass poles and an aluminum hub, shows improved reception compared to the author's previous transmit antenna. Key components include a conventional transformer for impedance matching and a variable resistance termination system to optimize performance. Despite challenges like nearby objects affecting signal patterns, the antenna consistently provides better signal-to-noise ratios, making it a valuable addition for low-band listening in suburban areas.

If RF noise threatens to take your hobby away, this could be probably a good solution to reduce or even eliminate RF Noise.

With high impedance earphones plugged into the audio jack on the Kenwood TS-590S or TS-590SG, you can hear a really annoying noise even with the AF volume set to zero. A simple quick-and-dirty solution is a resistor in series to the audio output.

This study details a reception comparison between vertical and horizontal active loop antennas, specifically two identical _Wellgood active loop antennas_, on various HF bands. The experiment, conducted in a densely populated QRM-prone area, monitored FT8 signals over a 24-hour period using two identical receivers. The methodology involved direct comparison of signal reception across the HF spectrum, aiming to identify performance differences based on antenna orientation. The results indicate that vertical loops demonstrated superior performance on higher bands (10m, 15m, 20m), while horizontal loops excelled on lower bands (30m, 40m, 160m), particularly for receiving long-distance (DX) signals. The horizontal loop's advantage on lower bands is attributed to potentially better low-angle performance and reduced sensitivity to man-made noise, yielding a **2-3 S-unit** improvement on 160m. The study provides practical insights for optimizing antenna placement in challenging urban environments, noting that the horizontal loop consistently showed a **10-15 dB** signal-to-noise ratio improvement on lower bands.

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.

An cheap and efficient wire antenna for lower HF bands. This closed loop antenna, radiates perpendicular to its plane with a bi-directional radiation pattern. With a gain of 2 dB over a diplole it is a low noise sensible antenna. Requires a tuner if you want to use as a multiband antenna.

Demonstrates the _Widget DX HB9HBY_ software, a compact desktop application for amateur radio operators, providing essential real-time information. The widget displays UTC time, current HF propagation conditions, local weather, and thunderstorm risk. It also integrates radio-related links and offers advanced PRO functions, such as a DX map, HF noise radar, IBP beacon synchronization, contest heatmap, aurora radar, and a rare DX radar. The software is available for Windows 10/11 and Linux, with a macOS version planned for future release, and supports both French and English interfaces. Author HB9HBY highlights the widget's simple installation process and automatic update capabilities, which can be silent for minor fixes or include notifications for significant changes. The free version provides core functionalities, while a 15-day free trial unlocks the PRO features. A lifetime PRO license is available for a one-time payment of CHF 10, activating advanced tools that help operators make quicker decisions at the station by correlating propagation, UTC, DX activity, and local conditions, though results remain indicative and require confirmation via listening or tools like _RBN_ or _PSKReporter_.

A small magnetic loop antenna, often employed by hams facing antenna restrictions or high local RFI, offers a compact solution for HF operation. This resource details the construction of a foldable magnetic loop designed for the 40m through 17m bands, emphasizing its high-Q factor and _Faraday coupling_ for effective noise rejection and narrow-band filtering. The guide outlines material selection, advocating for copper over aluminum to maximize efficiency, and provides insights into the physics governing its operation, including impedance matching and resonance principles. Practical application of this antenna design is particularly beneficial for QRP enthusiasts and portable operators seeking a stealthy, high-performance antenna. The construction process includes specific details for a 1-meter diameter loop, a 140pF variable capacitor, and a _gamma match_ for impedance transformation. Performance comparisons suggest that while a full-size dipole might offer slightly better gain, the magnetic loop's ability to mitigate local noise often results in a superior signal-to-noise ratio, making it a viable option for challenging RF environments.

IAT is an excel sheet table evaluate parameters of VHF UHF antennas edited by Vladimir UR5EAZ. The difference between this tool and the existing VE7BQH Antenna Table is the use of G / T and C / N instead of the G / Ta parameter. In this table, Vladimir applies the ITU recommendations to assess the noise properties of a radio receiving system and shows the advantage of the G / T concept over the G / Ta concept when choosing an antenna.

Ulrich L. Rohde N1UL conceived an outstanding 2m to HF receiving converter with specific requirements, including 144-148MHz to 28-32MHz coverage, low noise, high IP3, and a unique modular design. The design decisions emphasize modularity, absence of preselection, stability, and a passive mixer, showcasing Rohde's distinctive approach.

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.

The author describes his experience building and using a Beverage antenna for the 40-meter band. Despite encountering some challenges, the antenna offered some improvements in receiving stations compared to a 3-element inverted Vee antenna. The Beverage antenna showed a significant daytime signal-to-noise ratio improvement and received signals better than the Vee antenna. However, the front-to-back ratio was not ideal, and the transmit power seemed to affect the Beverage antenna. Overall, the author concludes that the Beverage antenna might be more suitable for locations with higher noise levels. The total cost of the antenna was around 30 Euros.