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137.7 kHz QRSS beacon exciter is described, utilizing a single chip for operation on the 2200m amateur band. The design focuses on simplicity and efficiency for weak signal applications, providing a compact solution for generating QRSS signals. This project targets the DX portion of the band, enabling long-distance communication with minimal power output. The resource details the construction and functionality of the **QRSS beacon**, emphasizing its **low-power operation** and suitability for experimental amateur radio. It provides insights into the circuit's architecture and potential for integration into existing station setups. The design aims to offer a practical and accessible entry point for amateurs interested in weak signal modes on the LF/MF bands.

Influence of the ionosphere on the EME signals by EAVQ

How do two-wire reversible direction Beverages work, an excellent document that explains fundamentals of beverage antennas. This article details the design and performance of a reversible beverage antenna. Leveraging orthogonality between common mode and differential mode currents on a 2-wire line, this antenna facilitates independent reception from both ends. While common mode signals arrive and are summed on a transformer's secondary for common mode reception, differential mode signals induce anti-phase currents, providing individual reception. Various measurements explore impedance, transmission loss, and F/B ratio, highlighting the antenna's effectiveness and areas for improvement. Notably, increasing the antenna's height significantly improved performance.

LEMO, established in 1946, specializes in high-performance interconnect solutions, offering an extensive range of over 50,000 circular connectors. Their product line includes the REDEL SP IP68 series, which features resin-free IP68 sealing for robust performance without complex potting processes. These connectors are critical for applications in medical, military, test and measurement, security, defense, and industrial sectors, ensuring reliable signal integrity in harsh conditions. The company designs, tests, and manufactures high-quality cable solutions, providing complete connectivity services such as custom cable assembly and signal integrity analysis. LEMO's solutions are integral to advanced scientific endeavors, as demonstrated by their use in CERN’s NA62 experiment for instrumentation and maintenance. LEMO's 80-year history, detailed in their anniversary publication, highlights their evolution from a Swiss family workshop to a global leader in connector technology. Their product finder tool assists customers in selecting appropriate connectors from their broad portfolio, which also serves audio-video, transportation, aerospace, and UAV applications.

GUI for the KK7KA Wolf software, that was originally written as command line interface only. Wolf is a weak signal software

Linux for shortwave and amateur radio monitoring. Supports popular SDR hardware and online streaming from KiwiSDR, WebSDR, and Spyserver sites. Articles about using Linux with your SDR devices.Skywave Linux, an innovative operating system, leverages cutting-edge technology for seamless access to radio signals globally. Ideal for regions with limited internet access, it effortlessly connects to a network of SDR servers, offering high-performance SDR operation without the need for extensive hardware. With pre-installed and configured SDR software, Skywave Linux simplifies signal discovery and operation for all users.

A 23 signal source project by W6PQL

BeaconSpot.uk provides an accurate, real-time picture of microwave and VHF/UHF beacons operating across Europe, alongside a worldwide listing of 6-meter beacons. The platform allows users to retrieve detailed data for individual beacons, facilitating in-depth analysis of signal characteristics and propagation paths. Interactive maps visualize beacon distribution by frequency band and display spot coverage for each station, offering a clear geographical overview of active beacons. The system integrates real-time DXCluster spots, sourced from contributors like Alain, ON4KST, and Pascal, F5LEN, and enables users to submit outgoing spots directly to the DXCluster. Beacon keepers can manage their beacon data, receive email alerts upon being spotted, and track their station's ODX (Outstanding DX) records. For every received spot, the distance to the beacon is automatically calculated and displayed, aiding propagation studies.

Solar activity can aid or hamper HF propagation beyond line-of-sight range, WA1SVF and N6BV answers to questions about Sun influence on radio signals propagation

A synthesized 2.3 GHz Amateur Television (ATV) transmitter design, conceived by Ian G6TVJ, is presented, targeting broadcast-quality video performance on the 13cm band and extending up to 2.6 GHz. The core of the design utilizes a commercial Z-comm Voltage Controlled Oscillator (VCO) that tunes from 2.2-2.7 GHz, providing a +10 dBm output and simplifying RF alignment. This VCO's stability, originally intended for narrowband applications, readily accepts high-frequency video modulation, contributing to the transmitter's robust performance. The exciter stage, incorporating a Mini Circuits VNA 25 MMIC amplifier, boosts the signal to +16dBm, while a Plessey SP4982 prescaler divides the output frequency for the synthesizer. The synthesizer employs a Motorola MC145151 CMOS parallel IC, favored over the common Plessey SP5060 for its superior video modulation characteristics and ease of programming without microprocessors. This choice addresses issues like LF tilt and distorted field syncs often seen with SP5060 designs, particularly when operating through repeaters or over long distances. The MC145151 divides the signal further, enabling precise frequency stepping, with programming handled by EPROMs for channel selection and LED display. The loop filter network, critical for video integrity, was developed through experimentation to prevent the PLL from reacting to video modulation, ensuring a clean transmitted picture. The transmitter incorporates a Down East Microwave commercial power amplifier module, delivering approximately 1.6W output, driven by the exciter through a 3dB attenuator. Construction involves surface-mount SHF components on micro-strip lines etched onto double-sided fiberglass board, housed within a tinplate box. The design boasts no AC coupling in the video path, preserving low-frequency response, a common failing in other ATV transmitters. Performance tests with a 50Hz square wave revealed no LF distortion, and a calibrated "Pulse & Bar" signal showed a near 100% HF response, demonstrating its capability for high-quality ATV transmissions.

This online project guide details the construction of a homebrew boom microphone system. It details the assembly of a microphone shell from a 3/4" PVC pipe section and an end cap, requiring a drilled hole for a snug fit of the electret or condenser mic element. The internal wiring schematic specifies a **2.2 K** resistor and a **47 uF** polar capacitor for signal conditioning, with a circuit diagram provided for integration with IC-706 series transceivers. The guide outlines the use of CAT-5 cable for internal connections, incorporating strain relief at the rear of the mic shell, and an inline 3.5 mm jack to facilitate an external _PTT_ line, designed for a foot-mounted switch. Further construction involves fabricating a microphone shock mount from a 2-inch PVC connector, detailing the creation of four "fingers" and the insertion of screw-eyes for attaching elastic bands, which are twisted 180 degrees for tensioning and vibration isolation. A foam wind screen is also incorporated into the microphone assembly, secured with adhesive. The boom arm itself is repurposed from an articulated architect lamp, with the original lamp assembly converted into a **60 watt** resistive load for testing power sources. Microphone cabling is secured to the boom arm using wire ties, ensuring sufficient slack at hinge points to maintain articulation. The boom base is mounted to a bookshelf, requiring specific positioning to achieve proper microphone placement in front of the operator. Performance evaluation of the microphone system is conducted through on-air audio signal reports from other amateur radio operators. DXZone Focus: Online Project Guide | Boom Microphone Construction | Electret Mic Element | PTT Line

This circuit is very simple and has a fantastic range of potential uses.

DTMF Electronics Manufacturer offers Decoding, Display, Signalling, Data Logging, Remote Monitoring and Control products and design.

The MMMonVHF database, curated by DL8EBW, currently lists 63,455 entries for VHF operators, providing a searchable resource for locating stations active on 144 MHz and higher bands. Operators can register their callsigns to be included, with specific criteria such as participation in _MS_ (Meteor Scatter), _WSJT_ modes, or _EME_ (Earth-Moon-Earth) operations required for inclusion in the `call3.txt` file. This resource facilitates VHF DX expeditions and contest planning by allowing users to identify potential contacts within a geographical area. The database supports various VHF/UHF operating modes, including those focused on weak signal propagation. Statistical data regarding the database entries is also presented, offering insights into the distribution of registered VHF activity.

1.5 dB of matched line loss can be calculated for a given transmission line using this online tool, which employs a model calibrated from empirical data. The calculator allows radio amateurs to input specific transmission line types, such as _RG-8_ or _RG-58_, and then determine the expected signal attenuation. This is crucial for optimizing antenna system efficiency and understanding power delivery to the radiating element, especially for HF and VHF operations where feedline losses can significantly impact performance. Beyond matched loss, the calculator also provides an estimate for mismatched loss if the Standing Wave Ratio (SWR) is specified. This feature helps operators quantify the additional power loss due to impedance discontinuities between the transceiver, feedline, and antenna, which is a common concern in amateur radio installations. Accurate loss calculations are vital for effective station design and for predicting actual radiated power. The tool's utility extends to various operating scenarios, from fixed station setups to portable deployments, aiding in the selection of appropriate feedline lengths and types to minimize signal degradation. Understanding these losses is a fundamental aspect of maximizing the effectiveness of any amateur radio antenna system.

Weak Signal Propagation Reporter Network Map and Database of WSPR data

VHF – Based on realtime APRS reports. This map shows real-time radio propagation from stations operated near 144 MHz. It uses data gathered by Automatic Packet Reporting System-Internet Service (APRS-IS) from packet stations in the amateur radio service. The map shows activity from the past hour. Paths are smoothed to create a color-coded footprint indicating the distance VHF signals are likely to be traveling.

A 102-inch vertical whip, commonly a CB antenna, forms the core of this low-profile 10-meter antenna design, optimized for the 28 MHz band. The construction details specify three 8-foot radials made from scrap wire, connected to a common point. This simple yet effective setup is designed for ease of construction and deployment, making it accessible for operators with limited space or materials. The design emphasizes using readily available components, including PVC pipe for the mast and a SO-239 connector for the feedline, ensuring a straightforward build process for a resonant quarter-wave vertical. Field results indicate that this antenna provides good performance for local and DX contacts on 10 meters, despite its compact footprint. The author, N8WRL, shares practical insights into its construction and tuning, highlighting its suitability for temporary or permanent installations where a full-sized antenna might be impractical. Comparisons to more complex designs suggest that this low-profile vertical offers a respectable signal-to-noise ratio and effective radiated power for its size, proving that simple designs can yield satisfying on-air results.

SPX Communication Technologies, operating under the TCI International brand, presents a range of radio frequency (RF) solutions primarily for government, defense, and commercial sectors. The offerings include advanced systems for spectrum monitoring, communications intelligence (COMINT), and high-frequency (HF) and medium-frequency (MF) broadcasting and communication antenna systems. Specific product lines encompass _Blackbird_ COMINT systems, _Scout_ spectrum monitoring receivers, and various antenna arrays designed for robust performance in challenging RF environments. The resource details the capabilities of these systems, such as wideband signal detection, direction finding (DF), and signal analysis, crucial for intelligence gathering and regulatory compliance. It also highlights the engineering behind their antenna designs, which are optimized for specific frequency ranges and operational requirements, including high-power broadcast applications and secure military communications. The information presented emphasizes the integration of hardware and software for comprehensive RF situational awareness. The company's focus on empowering partners to "Command the Spectrum" underscores its commitment to delivering critical tools for signal interception, analysis, and management across diverse operational landscapes.

Amplifiers, filters, attenuators, mixers, PLL, switches and frequency dividers, signal generators, power detectors, transimpedance amplifiers, variable gain amplifiers and more

Hints and Tips in using the Tigertronics SignalinkUSB External USB Sound Card and Interface

Manufacturers quality tone signaling, wildlife telemetry,avionics equipment,video transmision modems.

Gage applied technologies designs and manufactures high-speed data acquisition systems, high-speed digitizers in pci / cpci / pxi or pc oscilloscopes, providing utmost measurement fidelity for high frequency signals.

transmite equipment, collections of qrss signals received

New unused surplus and used electronic test and laboratory equipment including spectrum analyzers, signal generators and oscilloscope

Taken from April 1935 issue of QST page 60 where there is a short article on the origin of 73

This page has a collection of audio samples from unusual HF propagation phenomena, from round-the-world propagation to moonbounced signals , and to ducted transmission.

The Largest Selection of Cable Assemblies and Accessories. Coaxial Cables, Fiber Optic Cables, Connectors, Attenuators, Terminators, and Tools.

Improving your own signal quality by GM3SEK

CW-R Explained. CW reverse mode CW-R receives CW signals with a reverse side CW carrier point like that of LSB and USB modes

Receiver dynamic range is the ability of a receiver to receive a weak signal without loss of readability while a strong signal is present.

Amateur radio direction finding, transmitter hunting. triangulating a radio signal direction and plotting its bearing on a map. hunters use doppler systems for tracking hidden transmitters

The Kenwood TS-870S HF transceiver features two state-of-the-art 24-bit 20 MIPS DSP chips, providing over 100dB out-of-passband attenuation and CW bandwidth adjustable to 50 Hz. It operates across 160-10 meters with 100 watts output, incorporating digital filtering, a beat canceller, and 100 memory channels. The radio also includes a transmit equalizer, RX antenna input, and a K1 Logic Keyer, enhancing signal processing and operational flexibility for amateur radio operators. Advanced capabilities include IF stage DSP, dual noise reduction, and an auto notch filter, all contributing to superior signal reception and clarity. The TS-870S offers a variable AGC, voice equalizer, and an RS-232C port for computer control, with Windows™ software supplied. Its built-in automatic antenna tuner functions on all bands for both transmit and receive modes, streamlining station setup and operation. Available accessories such as the DRU-3A digital recording unit, SO-2 high stability crystal oscillator, and VS-2 voice synthesizer option further extend the transceiver's utility. The unit requires 13.8 VDC at 20.5 Amps and is supplied with an MC-43S hand microphone, making it a comprehensive station component.

It has been 40 years since the VHF-UHF Quagi antenna--a combination of the desirable features of a Yagi and a cubical quad--was developed and the design was first published in the newsletter of the Southern California VHF Club, a forerunner of today's Western States Weak Signal Society.

Makers of QRP HF General Coverage Transceivers you can build. The Home of BITX transceivers, uBITX General Coverage Receiver-Transmitter. A general coverage, 10 watts HF SSB/CW transceiver kit with features you NEED for operating ease, convenience and versatility. It works from 3 MHz to 30 MHz, with up to 10 watts on SSB and CW, with a very sensitive receiver.

The Icom IC-7300 is a groundbreaking Software Defined Radio (SDR) transceiver that revolutionizes the way amateur radio operators interact with the spectrum. With its large 4.3-inch color TFT LCD touch screen, users can easily navigate through various functions, including real-time spectrum scope and high-resolution waterfall displays. This allows for quick adjustments and enhanced signal awareness, making it easier to find and engage in QSOs. The touch screen interface provides a modern approach to radio operation, replacing traditional buttons with virtual controls that can be accessed with a simple touch. In addition to its user-friendly interface, the IC-7300 boasts advanced features such as IF-DSP filtering, audio scope functions, and a multi-dial knob that combines tactile control with touch screen flexibility. These capabilities enable operators to visualize signals and make precise adjustments to their settings, ensuring optimal performance during contests or casual operating. The IC-7300 is designed for both beginners and experienced hams, making it a versatile addition to any shack. Its innovative design and functionality truly embody the spirit of modern amateur radio.

Naptech buys and sells quality test equipment from hp, tektronix, including spectrum analyzers & peripherals, oscilloscope, frequency counters timers, signal generators, multimeters & voltmeters, RF & power meters, microwave amplifiers

IZ5CML, Enrico Giannerini, obtained his amateur radio license in 1998, achieving DXCC contacts with all entities over 18 years of activity. His station, located in Empoli, Tuscany, Italy, focuses on HF and 50 MHz operations, primarily using SSB, CW, and some RTTY. He emphasizes direct radio communication, preferring "human modes" over digital modes like FT8/4, which he views as detaching the operator from the signal. Enrico's operating interests include DXing, IOTA activations, and major HF contests, where he has participated both individually and with teams like IQ5LV and IO5O. Notable activations include Sao Miguel and Flores (CU8, EU-089) in the Azores in 2005, and Antiparos and Paros (EU-067) in Greece in 2006 and 2014. He also contributes to the Hamradioweb forum, promoting good operating practices and publishing the monthly "Dxschedule" for upcoming DX and contest activities. The website includes a blog with articles on DX, ionospheric propagation, and antennas, reflecting his long-standing passion for radio, sparked by the 1980s film "La Tenda Rossa" and years as an SWL.

Manufactures automatic mixers, analog and DSP signal processors, room combining and matrix mixers, and audio test equipment for just about any customer application.

The RFzero is a multi function signal platform developed for radio amateurs who wants to extend the Arduino skills in combination with RF. The RFzero board is largely compatible with the Arduino Zero and Arduino M0 boards, however, it has been carefully designed for flexible use in RF applications and with attention to the frequency spectrum and stability performance.

Signal generatos, oscillators, direct and indirect synthesizers, exciters custom oscillators

Homemade LC Bandpass Filters for 20M, 30M, 40M In multi-station environments like special events, field day, portable operating, is very important to protect receivers from excessively strong signals. Bandpass filters help to protect your transceivers.

The Utility DXers Forum (UDXF) provides a centralized platform for exchanging news and information concerning utility radio stations and signals operating within the 0 to 30 MHz spectrum. It specifically excludes broadcasting, pirate, and amateur radio transmissions, concentrating instead on a diverse array of other signals. The resource details the types of stations covered, including maritime coastal and ship stations, aeronautical ground and aircraft communications (voice, HFDL, Selcalls, Volmet), military operations, various beacons (NDB, driftnet, propagation, pirate, high-frequency), fax transmissions, numbers stations, diplomatic communications, clandestines, and other unusual signals. Further content addresses radar systems such as Over-the-Horizon, Ocean Wave, and CODAR, alongside ionosondes, chirpsounders, ALE-systems, Selcall-systems, and tone calls. Experimental stations and standard frequency and time stations are also within its scope. The forum also acknowledges utility radio-related amateur events like the International Lighthouse Weekend and Night of Nights, providing a broader context for listeners. The site offers sections for modes, hardware, software, a utility radio archive, digital BC & HF conditions, and a utility radio club archive, along with QSLs and pennants.

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.

Fifty-three digital modes, including PSK31, RTTY, and JT65, are explored in this resource, providing detailed descriptions of their underlying technologies and typical use cases. It covers error correction methods like ARQ in PACTOR and FEC in JT65, alongside modulation schemes such as FSK and PSK. The content highlights the evolution of digital communication from traditional TNC-based systems to modern sound card implementations, emphasizing the role of personal computers in advancing these modes. Specific modes like AMTOR, PACTOR, and G-TOR are discussed, noting their baud rates and error correction capabilities. For instance, AMTOR operates at 100 baud, while PACTOR offers 200 baud with Huffman compression. The article also delves into newer modes like MFSK16, which uses 16 tones and continuous Forward Error Correction, and Olivia, capable of decoding signals 10-14 dB below the noise floor. Each mode's bandwidth, speed, and resilience to propagation challenges are examined, such as MT63's 1 KHz bandwidth and 100 WPM rate, or Hellschreiber's 75 Hz bandwidth and 35 WPM text rate. The resource also lists predominant USA HF digital frequencies for bands like 160, 80, and 40 meters, specifying segments for PSK31, RTTY, SSTV, and Packet. It includes links to freeware and shareware sound card software such as Digipan, FLDigi, and MixW, enabling amateurs to experiment with these modes.

Selecting appropriate coaxial cable and wire for demanding amateur radio applications, particularly those involving high power or harsh environmental conditions, is crucial for maintaining signal integrity and operational safety. This resource details Harbour Industries' specialized offerings, which include Mil-Spec and commercial designs such as NEMA HP3/HP4 and SAE AS22759, suitable for aerospace, military, and industrial sectors. Their product line addresses the need for robust conductors capable of withstanding extreme temperatures and mechanical stress, often encountered in antenna systems or amplifier interconnections. The company highlights its AeroPOWER® Firezone M25038/3 cable, specifically engineered for high-temperature environments like aircraft engines. This particular product exemplifies their focus on solutions for critical infrastructure where reliability under adverse conditions is paramount. Such cables are relevant for hams building or maintaining stations in challenging climates or those operating high-power amplifiers where internal wiring must endure significant thermal loads. Harbour Industries also provides a range of high-performance cables designed to meet stringent specifications. Their expertise in high-temperature and high-performance cable manufacturing positions them as a supplier for specialized wiring needs beyond standard off-the-shelf options, ensuring durability and performance for advanced amateur radio setups.

Linrad and SDR-IQ Software Defined Receiver on Shortwave

Always wanted to know what kind of sounds we hear, when listening to the radio? Here are some examples

A simple DIY signal generator based on NorCal QRP club kit

April instrument, manufacturer of programmable microwave signal generators