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CwGet v2.55 is a software application for amateur radio operators designed to decode Morse code (CW) signals into text using a standard computer sound card, eliminating the need for specialized hardware. The program features a customizable interface with a spectrum display for visualizing signal frequencies and peaks, an oscillogram for monitoring signal presence and setting detection thresholds, and a received symbols window for displaying decoded text. Key functionalities include Automatic Frequency Control (AFC) to lock onto signals, adjustable FIR and IIR filters for noise reduction, and a burst filter to mitigate short noise impulses. It also supports automatic CW speed detection, multiple character sets, and the ability to record and replay received audio. Integration with logging software like AALog is facilitated through double-click word transfer, and transceiver frequency control is possible via the Omni-Rig interface, allowing for automatic tuning of the radio's VFO or RIT. The multi-channel decoder feature can simultaneously decode up to five strong signals within a 1600 Hz bandwidth, displayed in a separate Multi-RX Window with an adjustable squelch. CwGet also offers the capability to decode signals from pre-recorded WAVE files and can function as a narrow-band sound DSP filter for aural decoding. This is a commercial version and it has been tested on latest MS Winows versions.

Logger32 is a well-established amateur radio logging program designed primarily for DXers who require a flexible and data-driven logging environment. The software maintains a comprehensive logbook database capable of handling large volumes of QSOs while offering detailed tracking of DXCC entities, awards, and band/mode statistics. One of the core strengths of Logger32 is its DX cluster integration. The program connects to telnet DX clusters and displays spots in real time, with filtering options by band, mode, country, or callsign. The cluster window can automatically highlight needed DXCC entities, band-fills, or new modes based on the operator’s log. Logger32 also provides rig control through CAT interfaces, supporting a wide range of transceivers via serial or USB connections. When properly configured, frequency and mode are automatically captured in the log entry window. The software supports digital mode integration through external applications and can exchange information using standard interfaces. Another important feature is its award tracking system, including DXCC, WAS, IOTA and other common amateur radio awards. The program calculates worked, confirmed, and needed entities with detailed reports. Logger32 supports ADIF import and export, allowing interoperability with other logging systems. It also includes QSL management, with tracking for bureau, direct, and electronic confirmations such as LoTW or eQSL when configured. Overall, Logger32 remains a technically capable logging solution focused on DX tracking, cluster awareness, and detailed statistical analysis of operating activity.

Audio Spectrum Analyser Spectrum Lab or Speclab started as a simple FFT program running under DOS a long time ago, but it is now a specialized audio analyzer, filter, frequency converter, hum filter, data logger and more. Can be used for MTHELL QRSS, DFCW, PSK, MSK, Castle. Spectrum Lab is a free audio analysis tool, lets you see the hidden world of sound. It analyzes live audio or recordings, showing you the exact frequencies present. Watch sounds change over time with a waterfall display. Need to clean up your audio? It can filter out noise in real-time. Even play with radio signals by decoding and creating special modes! While ideal for amateur radio enthusiasts, anyone can explore the science of sound for free.

DX clusters aggregate real-time amateur radio spot data, enabling operators to identify active stations and propagation conditions across various bands and modes. DXWatch offers a web-based interface for this essential operating tool, allowing users to filter spots based on specific criteria such as band, mode, or callsign. The service integrates features like a customizable filter system and an external widget for embedding spot data on other platforms, enhancing its utility for DXers and contesters. Operators can access worldwide spot data, with options to zoom into specific regions like the US, Europe, or the North Atlantic, facilitating targeted DXing efforts. The platform also includes a watchlist feature for registered users, enabling personalized tracking of desired stations or entities. Real-time data on solar flux index (SFI), A-index, and K-index are displayed, providing crucial propagation insights alongside the DX spots.

Monitoring shortwave broadcast stations effectively requires accurate schedule information to identify transmissions. This online utility offers a straightforward, graphical interface designed to search for and display current shortwave radio broadcasting schedules. Users can precisely filter results by frequency, specific language, broadcaster, time of day, and even by shortwave band, which simplifies the process of pinpointing desired content. The database, last updated on March 26, 2023, details station callsigns (e.g., BBC), start and end times in UTC, days of the week, broadcast language, transmitter power in kilowatts, and azimuth. Crucially, it includes the precise geographical coordinates of transmitter sites, such as Woofferton in the UK or Al Seela in Oman. This data is invaluable for predicting signal paths and optimizing antenna direction for improved reception, a key consideration for serious SWLs. For instance, a search for BBC English broadcasts at 21:04 GMT quickly reveals multiple active frequencies like 17780 kHz from Woofferton, offering a clear overview of current transmissions. The tool processes queries rapidly, returning results within seconds, demonstrating its efficiency for broadcast listening enthusiasts seeking timely information.

Over 25,000 amplifiers and sub-assemblies were produced by Angle Linear for the communications industry over a 40-year period. The company specialized in **high-linearity RF products**, focusing on preamplifiers, bandpass filters, and receiver multicouplers. Specific product lines included PHEMT and GaAs FET preamplifiers, offering both quadrature and single-ended configurations for various signal levels. The offerings encompassed coaxial and combline bandpass filters, along with integrated filter-preamplifier assemblies. The company also provided custom RF assemblies, addressing applications such as MRI preamplifiers, passive radar, and EME (moon bounce). Their product range covered VHF and UHF frequencies, including specific designs for 2m, 70cm, and 23cm bands, often featuring high IP3 performance. Technical documentation, such as filtering application notes and duplexer theory, was also associated with their product offerings.

Presents a web-based DX cluster interface, F5LEN Webcluster, which functions as a member node within the broader European DX Cluster network. It displays current DX spots across a wide range of amateur radio bands, from VLF through SHF, including specific bands like 1.8 MHz, 144 MHz, and 10 GHz, as well as satellite operations on QO-100. The service offers filtering options for various modes and activities, such as CW, QRP, IOTA, and specific VHF/UHF bands. Operators can access real-time propagation data, including Solar Flux Index (SFI), Sunspot Number (SSN), Kp index, and Auroral activity (Au), alongside tools for solar forecasts and tropospheric ducting predictions. The platform facilitates DX spotting by providing a centralized point for sharing and viewing contact information, aiding in DX hunting and contest operations. It also includes links to an Atlas, Sun tools, and a mobile version for portable access.

Circuit diagram and discription of 7 MHz Ham Radio SSB Transceiver. Transceiver using two MC1496, 4.43 MHz Ladder filter, LM386, LM324 and IRF840 in final.

Log4OM is a free logging software designed for amateur radio operators who require an integrated environment for station management and QSO logging. It is widely used by DXers due to its strong database capabilities and its integration with common online services. The program uses a structured SQL database and supports large logbooks without noticeable performance degradation. One of its key features is **CAT Control**, which allows direct communication with many transceivers for automatic frequency and mode detection. The **DX Cluster Client** provides real-time spotting with filtering and band/mode tracking, helping operators quickly identify new DX opportunities. Log4OM integrates with several external confirmation systems. Built-in support for **Logbook of The World (LoTW)** and **eQSL** allows automatic upload and download of confirmations. The software also includes **Award Tracking**, enabling operators to monitor progress toward DXCC and other award programs directly from the log. Additional capabilities include **Callbook lookup** via services such as QRZ, **ADIF import/export**, and customizable **QSL management** for both electronic and paper cards. The interface is modular, with panels that can be arranged depending on operating preferences. Log4OM does not include integrated digital mode engines, so digital operation normally relies on external programs such as WSJT-X or FLdigi connected through standard interfaces. Overall, Log4OM provides a comprehensive logging environment suitable for both casual operation and serious DX chasing, with a feature set comparable to many commercial logging applications.

CW Skimmer 2.1 employs a high-sensitivity CW decoding algorithm based on Bayesian statistics, enabling simultaneous decoding of up to 700 CW signals within a receiver's passband on a 3-GHz P4 system when paired with a wideband receiver. The software features a fast waterfall display with sufficient resolution for visual Morse Code interpretation, automatically extracting and labeling callsigns on the waterfall traces. Extracted callsigns are exported as DX cluster spots via an integrated Telnet cluster server. The application includes a DSP processor with a noise blanker, AGC, and a variable-bandwidth CW filter, alongside an I/Q Recorder and player. It supports both 3 kHz radio passbands and wideband SDR receivers like SoftRock, RF Space SDR-IQ/SDR-14, SRL QuickSilver (QS1R), HPSDR Mercury, and Microtelecom Perseus. System requirements specify Windows XP/7/8/10 (32-bit or 64-bit), a Pentium-4 2.5 GHz for wideband operation or 1 GHz for 3-kHz radios, a COM port for CAT control, and a stereo sound card supporting 48 kHz sampling. It integrates with Elecraft KX3, Icom IC-7300/IC-7610, and Flex 6000 series radios, with documentation available for various setup configurations.

Demonstrates BBLogger, a **freeware** logging application designed for both amateur radio operators and Short Wave Listeners (SWLs). Developed by IK2VIW, IZ2BKT, and IK2UVR, this software provides comprehensive station management capabilities, including **CAT control** for various transceivers, integration with digital mode software like WSJT-X, JTDX, and MSHV, and robust QSL management features. The application supports a wide array of functions such as DX cluster interfacing, mapping, awards tracking (including custom awards), and direct integration with services like LoTW, eQSL.cc, and ClubLog for QSL confirmations and OQRS requests. It also includes utilities for ADIF to CSV conversion and vice-versa, catering to diverse logging and data management needs. Recent updates, such as version 13.1, introduce a web server for log management from any device, allowing remote access and control. The software has improved ADIF import capabilities, including time settings for duplicate QSO detection, and enhanced filtering options for log searches. Performance improvements include faster automatic updates and manager database synchronization, along with optimized log checking at startup. Earlier versions added support for FT8 and FT4 modes, refined OQRS integration with ClubLog, and expanded QSL/label printing functionalities, enabling users to select specific callsign types (OM, SWL) for printing. The developers emphasize compatibility with Windows 10/11 for full functionality, noting limitations when running on older operating systems like Windows 7 due to modern security protocol requirements.

Facilitates efficient logging of amateur radio contacts, offering a robust solution for hams managing their station activities. The software integrates _CAT control_ capabilities, allowing direct interfacing with popular transceivers from manufacturers like Yaesu, Icom, and Kenwood. This feature streamlines the logging process by automatically capturing frequency, mode, and other QSO details directly from the radio, reducing manual entry errors and improving operational efficiency during contests or DXing. _HAM-LCT_ includes a comprehensive database, enabling users to store and retrieve contact information, QSL data, and other relevant details for each QSO. The program supports various operating modes and provides tools for searching and filtering log entries, which is beneficial for award tracking and station analysis. Its design focuses on providing a user-friendly interface for everyday logging tasks. While the original author, _HB9CQV_, has discontinued development of HAM-LCT in favor of a newer logging application, this version remains available as a functional freeware option for Windows users seeking a dedicated logbook with integrated rig control.

The most flexible and powerful Microwave and RF Filter and Multiplexer Design Software. Download Filpro-student.zip

AEA Technology Inc. is a pioneer and leading manufacturer of RF and cable test equipment for the wireless, Telco, CATV, NMR & MRI, RFID, telemetry, aviation, commercial, military, and two-way radio industries. Produces SWR Meters, Pre Amplifiers, filters, power meters and antenna testing products

Technical reference about Accessories, Amplifiers, Antennas, Cable and Connectors, Filters, Geography, Grounding, Gunk, Matching Networks, Projects, Propagation Info Radios, RFI/EMI, Rotors, Station Setup, Towers.

adsbScope is a freeware Windows application designed for processing _ADS-B_ (Automatic Dependent Surveillance-Broadcast) frames received from a compatible decoder. It identifies aircraft, calculates their real-time positions, and presents flight parameters in both alphanumeric tables and a graphical display. The software interfaces via a virtual COM port, receiving raw frames to provide detailed situational awareness, including a global coordinate grid, continental coastlines, over 4,000 **airport** locations, and major cities. Users can overlay OpenStreetMap tiles and view world state boundaries, with each tracked aircraft rendered with labels showing altitude, speed, heading, squawk code, and flight identifiers. When paired with the adsbPIC-decoder, adsbScope enables advanced hardware control, allowing users to toggle data filters for specific frames like DF17/18/19, adjust analog signal thresholds for reception fine-tuning, and manage system resets or bootloader activation directly from the PC. This functionality provides a customizable toolkit for hobbyist radar listeners, offering a robust alternative to commercial tools for processing aircraft data. The software displays up to **1090 MHz** transponder data and can track aircraft up to 250 nautical miles.

The Elecraft K3, a popular HF transceiver, is often benchmarked against new market entrants. This article critically compares the Kenwood TS-590S to the K3, focusing on key technical specifications and operational aspects relevant to serious amateur radio operators. The author proposes three distinct evaluation methods: a circuit diagram comparison, an independent review analysis (referencing Peter Hart, G3SJX, in RadCom), and a real-world "ear test" by experienced contest operators on 40 and 80 meters. The analysis delves into specific receiver components, including the first mixer design, RF and IF amplifier performance, and the presence of an image noise filter. It highlights the K3's switched mixer and the potential for the TS-590S to utilize similar or improved designs, such as a classic filter with enhanced selectivity. The article also scrutinizes the second mixer stage, noting the K3's SA612 chip and its associated IP3 limitations, suggesting Kenwood might achieve benefits with a different mixer architecture. Further points of comparison include DSP capabilities, where the K3's high-performing DSP with KK7P's involvement is noted against the TS-590S's potential reliance on newer IC technology but possibly less refined software. The discussion extends to DDS and PLL implementations for phase noise and spurious emissions, and the utility of a second receiver for DX chasing and contesting, acknowledging its importance for some operators while being less critical for others. The article concludes by emphasizing personal preference in equipment selection.

Do your multiple-transmitter field day or contest efforts suffer from intrastation interference ?

Demonstrates the construction of a **homebrew spectrum analyzer** designed by Wes Hayward, W7ZOI, and Terry White, K7TAU, enabling radio amateurs to build a capable test instrument without significant expense. The resource details a _double-conversion superheterodyne_ circuit, employing intermediate frequencies of 110 MHz and 10 MHz, and covers essential blocks such as the time base, logarithmic amplifier, resolution filters, and local oscillators. It highlights the use of hybrid and monolithic ICs, including mixers, amplifiers, and VCOs, to simplify construction while maintaining performance. The design supports useful measurements in the 50 kHz to 70 MHz range, with methods outlined for extending capabilities into VHF and UHF. The authors emphasize that this analyzer, while simple to build, is intended for serious measurements, requiring careful control of signal levels to avoid spurious responses. It uses an oscilloscope for display, with specific instructions for calibration and adjustment of various stages, including the log amplifier and IF gain. The guide provides detailed schematics and component lists for each section, such as the 110 MHz triple-tuned band-pass filter, which achieved **90 dB** image rejection, a significant improvement over double-tuned circuits. Practical advice on alignment and troubleshooting is included, drawing on the authors' extensive experience in RF circuit design.

Over 75 years of engineering expertise underpins Bird Electronic's offerings in RF power measurement, critical for maintaining peak performance in amateur radio stations and professional communication systems. The company specializes in a range of test equipment, including wattmeters, SWR meters, and antenna analyzers, essential for optimizing antenna systems and ensuring efficient power transfer. Their product line extends to various RF components such as filters, cables, and connectors, all designed to meet stringent technical specifications for reliability and accuracy across diverse frequency bands. Bird Electronic's instruments, like the _Bird 43_ Thruline Wattmeter, are widely recognized for their robust construction and precise measurement capabilities, providing hams with confidence in their station's operational parameters. These tools enable accurate assessment of forward and reflected power, SWR, and modulation characteristics, which are vital for troubleshooting and maximizing radiated power. The company's commitment to innovation ensures that its products remain relevant for modern RF challenges, from HF through microwave applications, supporting both traditional analog and advanced digital modes.

HotPaw MorseDecoder, an iOS application, provides real-time translation of Morse Code audio signals into plain text, leveraging the device's microphone or headset input. It incorporates a DSP narrow-band audio filter, adjustable from 300 to 2400 Hz, to mitigate background noise and QRM, enhancing signal clarity for decoding. The application offers both an automatic decoding mode and manual controls for fine-tuning parameters such as audio filter frequency, WPM dot/dash speed, noise threshold, and Farnsworth timing. The WPM detection automatically adapts from 8 to 40 WPM, with a QRQ High Speed mode extending this range to 30-80 WPM for faster code. A built-in spectrogram aids in identifying the precise audio frequency of the CW tones. User feedback indicates effective performance with various transceivers like the Yaesu FT-857 and Icom IC-R8600, particularly when manual settings are optimized. The app's ability to visually tune stations within the passband and decode speeds beyond an operator's manual capability has proven beneficial during contests and general QRP operation.

Demonstrates CW Decoder Logic, a freeware application for Windows Vista SP2, 7, 8, and 10, designed to decode Morse code signals. The software incorporates an optimized 80 Hz DSP filter, enabling reception of CW signals across a speed range of 5 to 60 WPM. Key features include automatic signal tracking within a 3 KHz range, real-time speed detection, and an auto squelch function, enhancing decoder sensitivity and accuracy. The application provides station selection directly on a waterfall display and includes a "Tips" feature for word annotations. It supports sending decoded text to external logging software via UDP protocol, with a logger source code example provided for developers. Configuration options allow users to set speed limitations and customize interface elements. Released initially on October 17, 2016, with subsequent updates, the program requires Microsoft .NET Framework 4.5 or higher. Changelogs detail improvements such as increased program stability, code optimizations for speed, and fixes for display issues across different Windows versions.

Constructing a Lindenblad antenna for 137MHz NOAA satellite reception involves specific design considerations for optimal performance. The resource details the use of 4mm galvanised steel fencing wire, 300-ohm television ribbon cable, and wood/plastic components for the antenna structure. Key dimensions for a 137.58MHz-resonant antenna are provided, derived from the ARRL Satellite Handbook, specifying s, l, w, and d as 42, 926, 893, and 654mm respectively. The antenna is designed for Right Hand Circularly Polarised (RHCP) signals, requiring the four folded dipole elements to be tilted clockwise by 30 degrees. A significant aspect covered is impedance matching between the antenna's 75-ohm impedance and a typical 50-ohm receiver input. A twelfth-wave matching transformer, constructed from 117mm sections of 50-ohm RG-58 and 75-ohm RG-59 coax with a 0.66 velocity factor, is described. The article also addresses coaxial cable and connector selection, recommending 75-ohm Type-N connectors for RG-6 cable in professional setups and F56/F59 connectors for general use, while strongly advising against PL-259/SO-259 connectors for VHF. Strategies for mitigating Radio Frequency Interference (RFI) are discussed, including antenna placement to shield from local TV transmitters and the use of commercial or DIY band-pass filters, such as cavity resonators or helical notch filters, along with ferrite chokes on coaxial cables. Antenna orientation is explored, noting the Lindenblad's 'cone of silence' directly overhead and its maximized sensitivity towards the horizon. An experimental vertical tilt of 90 degrees is presented as a method to improve overhead reception and reduce interference from strong horizontal signals, particularly relevant in high RFI environments like the Siding Spring Observatory site.

The RigPix database entry provides a comprehensive technical overview of the Icom IC-746 amateur HF/VHF transceiver, detailing its operational parameters and physical characteristics. It specifies the transmit frequency ranges across 10-160 meters plus WARC bands, 50-54 MHz, and 144-146/148 MHz, alongside receive coverage from 0.03-60 MHz and 108-174 MHz. The resource outlines supported modes including AM, FM, SSB, CW, and RTTY, noting a tuning step resolution down to 1 Hz and a frequency stability of ±5 ppm. Key electrical specifications are presented, such as a 13.8 VDC power supply requirement, current drain figures for RX (1.8-2 A) and TX (Max 20 A), and RF output power ranging from 5-40 W for AM and 5-100 W for FM, SSB (PEP), and CW. The entry details the triple conversion superheterodyne receiver system, listing IF frequencies at 69.01 MHz, 9.01 MHz, and 455 KHz, along with sensitivity ratings for various modes and bands. Transmitter section specifics include modulation systems and spurious emission levels. Additional features like a built-in auto ATU, electronic keyer, simple spectrum scope, DSP, and CI-V computer control are noted. The page also lists related documents, modifications, and an extensive array of optional accessories, including various filters, microphones, and external tuners, providing a complete profile of the IC-746.

The Adonis Electric Co., Ltd. catalog details a range of amateur radio microphones, including mobile, desktop, and bike-specific models, alongside essential accessories. Featured products include the _FX-6_ flexible microphone and various interconnecting cables designed for seamless integration with transceivers from Icom, Yaesu, and Kenwood. The catalog also presents specialized items like microphone selectors, alternator noise filters, and peripherals such as voice memory units and double VOX controllers, enhancing operational flexibility for hams. These products are engineered to improve audio clarity and operational convenience for amateur radio operators, particularly in mobile and fixed station environments. The inclusion of conversion codes ensures compatibility across major transceiver brands, simplifying setup. The alternator noise filter addresses common mobile RFI issues, contributing to cleaner signal reception and transmission, which is crucial for effective DXing and contesting.

Constructing a functional spectrum analyzer for the 0-100 MHz range presents a significant challenge for radio amateurs, often requiring specialized components and careful calibration. This project details a homebrew spectrum analyzer design utilizing common integrated circuits like the _SA605D_ FM receiver IC and _MAR-6_ MMIC amplifiers, aiming for a cost-effective solution. The design incorporates a low-pass filter, RF amplification, a voltage-controlled oscillator (VCO) for downconversion, and multiple IF stages at 150 MHz and 10.7 MHz, with a resolution bandwidth (RBW) of 15 kHz. Critical components such as the _SBL-1_ mixer and varicap diodes are specified, alongside instructions for winding inductors and tuning filters. The analyzer's performance is discussed in terms of input level limitations, specifically the 1dB-compression point and third-order intercept point, to ensure accurate measurements and prevent component damage. The _SA605D_'s logarithmic Received Signal Strength Indicator (RSSI) output serves as the detector, driving the Y-input of an oscilloscope, while a _TL084_ op-amp generates the sweep signal for the X-input. Potential enhancements include adding a step attenuator, improving front-end filtering, and implementing switchable IF filters for variable RBW, allowing for greater versatility in analyzing RF signals.

High speed silicn diodes work well as RF switches. This article describes how to use diodes for selecting two or more filters ARRL QST article by W1FB

A circuit that connects an IBM compatible personal computer, running TR Log or CT (etc.) contest logging software, and Kenwood transceivers equipped with serial control ports. CW keying is also provided in this RFI filtered interface unit.

HD Communications Corp specializes in **RF and microwave amplifiers** engineered for demanding communication, defense, and industrial applications. Their product line includes precision-built, high-power solutions, along with RF connectors, filters, HF cables, and various accessories. The company also supplies tower hardware, valves, and tubes, catering to a broad spectrum of radio frequency infrastructure needs. Beyond amplifiers, HD Communications offers a range of **RF filters**, including low-pass filters, antenna filters, and solutions for RFI/TVI mitigation. Their inventory encompasses essential components like coaxial cable and various connector types, supporting both amateur radio and professional installations. The company operates as a manufacturer and vendor, providing direct sales of its specialized RF products.

Demonstrates practical solutions for reducing **Radio Frequency Interference (RFI)** in amateur radio operating environments, specifically addressing issues with PC monitors, receivers, and transceivers. The resource compiles advice from experienced operators regarding the selection and application of ferrite cores, including split cores and toroidal cores. It details specific material types like **43, 73, 75, and 77 ferrite**, outlining their effective frequency ranges for RFI suppression, such as 43 material for 30-400 MHz and 77 material for 2-30 MHz. The content provides part numbers for various ferrite products from manufacturers like Fair-Rite Products Corp, distributed by Amidon, and discusses their impedance characteristics across different HF bands. It compares the performance of various ferrite materials at frequencies like 4 MHz, noting that 75 material offers 27 ohms, 73 material 17 ohms, and 43 material just under 10 ohms. Additionally, it touches upon the use of bypass capacitors in conjunction with ferrites to create low-pass filters, emphasizing the importance of identifying common-mode versus differential-mode RFI paths for effective mitigation.

Supplier of custom designed, high performance quartz crystal filters for communications receivers and transceivers, for Yaesu Icom Kenwood and Collins radios

One specific challenge in the KazShack, operating Single Operator Two Radios (SO2R), involved sharing a K9AY receive antenna between two transceivers without direct RF connection or manual feedline swapping. The solution, detailed in this project, adapts the **W3LPL RX bandpass filter** design to split 160m and 80m signals, feeding them to separate radio inputs while maintaining isolation. This approach also addresses the issue of strong broadcast band interference from a nearby 50KW WPTF transmitter on 680kc. The construction utilizes T-50-3 toroids and NP0 ceramic capacitors, built in a "dead bug" style on copper clad board. Each band's filter coils are identical and resonated to the desired frequency using an MFJ-259 antenna analyzer. A single DPDT relay, controlled by a remote toggle switch mounted on an aluminum panel, facilitates quick band switching between radios, simplifying low-band operations. While some signal loss is noted, the expected lower noise levels from the receive antenna are anticipated to compensate, potentially reducing the need for constant volume adjustments during toggling between transmit and receive antennas.

This is a 6 band receive only filter designed to protect your receiver front end and provide 45dB reject at the stop bands. This is a 6-band receive only filter designed to protect your receiver front end and provide 45dB reject at the stop bands. Stop band reject may be limited by the relay isolation. Worse case isolation is at 28 MHz or 35 dB or better. Relay K3/K8 protects the filter during transmit via the PTT line. A 25-50ms delay must be used between transmit and PTT. Do not rely on your radio to provide adequate delay with out using the PTT. You logging software must be set to allow a delay between PTT and time of 1st transmit. This filter will not work with VOX or QSK keying as you will damage the filter.

CWRX, a freeware Windows application, decodes Morse code (CW) signals directly from a sound card's audio input, presenting the decoded text on screen. It supports various receive bandwidths and filtering options, allowing operators to optimize signal reception in different QRM conditions. The program's core functionality focuses on robust CW decoding algorithms, crucial for weak signal work and contesting environments. Developed by OZ1IVA, Lars Harbo, this utility provides a straightforward interface for real-time CW interpretation. It integrates basic logging capabilities, enabling users to record decoded transmissions for later review or contest submission. The software is specifically tailored for the Windows operating system, ensuring compatibility with common shack computer setups. Its design emphasizes ease of use for amateur radio operators seeking a dedicated CW decoding solution. The program's small footprint and direct functionality make it a practical tool for both casual listening and more intensive operating sessions, without requiring extensive system resources.

The QLF filter is a microprocessor based interface designed to go between a standard Morse code key and a radio transmitter

Over 15 years of experience in DXing and contesting informed the development of _DXHeat_, a responsive web DX Cluster and analytics platform. This service delivers real-time DX spots, accessible on both desktop and mobile devices, featuring intuitive filtering capabilities. Users can quickly narrow down spots by band, mode, or specific callsign, streamlining the search for rare DX or contest multipliers. The platform integrates data from various sources, including traditional telnet clusters, the Reverse Beacon Network (_RBN_), and _PSK Reporter_, offering a comprehensive view of propagation and activity. Beyond live spotting, DXHeat provides extensive cluster analytics for individual callsigns, allowing operators to research past activity and propagation trends. This deep dive into historical data can be particularly useful for planning future DXpeditions or optimizing contest strategies. The interface is designed for serious DXers, prioritizing quick access to relevant information and robust data analysis.

TX RX Systems Inc. offers a robust catalog of RF conditioning products, including **transmitter combiners**, receiver multicouplers, and various RF filters. Their extensive experience, spanning over 45 years in the RF and Land Mobile Radio (LMR) industries, underpins their specialized offerings. They provide solutions for in-building RF coverage, repeater systems, and general RF management, catering to the demanding requirements of professional radio communications. Their product line features **bidirectional amplifiers (BDAs)**, signal boosters, and cavity filters, essential components for optimizing radio system performance. The company emphasizes reliable solutions, leveraging decades of field-proven expertise in designing and manufacturing critical RF infrastructure. From duplexers to cell enhancers, TX RX Systems focuses on delivering high-quality RF components and integrated systems designed to ensure clear and consistent radio signal integrity across diverse operational environments.

The document is a technical guide on designing RF filters for radio frequency applications. It covers topics such as interference suppression, band-pass filters, and low pass filters, with a focus on filter design and circuit filters.

The Super Check Partial database files provide a list of callsigns used by active contesters. The data comes from Cabrillo logs contributed by contesters themselves. Contributed logs from the past 24 months are used to create the database. These logs are combined and filtered so that they result in a fairly good (but not perfect) list. The files do not contain any QSO data, such as state, CQ zone, Maidenhead Grid Locator, etc. The dta files can be used with CT, WriteLog, TRlog, SD, N1MM Logger, NA, Win-Test, and others

RFAC Solutions specializes in providing a range of RF components, including various connector types, cable assemblies, attenuators, and filters. Their product line features common connector standards such as SMA, BNC, TNC, N-Type, MCX, and MMCX, essential for reliable RF signal paths in amateur radio and commercial applications. The company also offers high-power VHF amplifiers, catering to needs for signal boosting in specific frequency ranges. Their offerings extend to dust caps and adapters, which are crucial for maintaining the integrity and versatility of RF systems. The focus on supplying components from South Korea suggests a commitment to specific manufacturing standards and supply chain practices. This resource details a vendor's product scope, useful for hams sourcing specific parts for shack builds or antenna projects. Jeff is listed as a contact for inquiries.

A range of easy-to-build RFI filters by John Regnault, G4SWX

UK manufacturer of ham radio accessories, including TNX, SDR receivers, RF Diplexers Triplexers, bandpass filters, iambic memory keyers.

Radio frequency systems require robust protection against transient voltage events, which can severely damage sensitive equipment. This resource details a range of **RF surge protection** devices, including models with DC Pass, DC Block, Bias T, and Ultra Low PIM characteristics, designed to safeguard critical infrastructure. It also presents various RF filtering solutions and interconnect components, emphasizing their role in maintaining signal integrity and operational continuity across diverse applications. The site provides information on products engineered for both RF and data line protection, highlighting their utility in preventing downtime and equipment loss. Specific product categories encompass coaxial protectors, grounding items, and fiber optic solutions, indicating a broad scope of application from amateur radio installations to industrial and telecommunications networks. Furthermore, the resource mentions the availability of NOM-certified products and offers same-day shipping for many items, underscoring a commitment to rapid deployment and compliance with industry standards.

Industrial Communication Engineers (ICE) was a manufacturer specializing in **RF components** and solutions for amateur radio and commercial applications. Their product line included a range of RF parts, various types of filters, and RF switching products designed to enhance station performance and mitigate interference. These components were critical for hams engaged in contesting, DXing, or general operating, providing means to improve signal integrity and manage complex antenna systems. The company's offerings addressed common operational challenges such as RFI and TVI, with products like **low pass filters** and antenna filters. While the specific technical specifications of their product range are no longer available, such components typically provided significant attenuation of unwanted harmonics and out-of-band emissions, crucial for maintaining a clean signal and preventing interference with other electronic devices. The current status indicates the domain is for sale, suggesting the manufacturing operations have ceased.

A 4 AMP / 18V regulated power supply schematic, designed by _ON6MU_, provides a detailed circuit diagram for constructing a robust power source. The design focuses on delivering a stable 18-volt output at up to 4 amperes, crucial for powering various amateur radio equipment. This resource presents a clear visual representation of component interconnections, including rectifiers, filter capacitors, and voltage regulation stages, essential for DIY enthusiasts building their shack infrastructure. The schematic's clarity facilitates understanding the power flow and component roles within the circuit. This circuit design offers a practical solution for hams needing a reliable 18V supply, potentially useful for driving specific transceivers, amplifiers, or accessory circuits. While specific performance measurements or comparisons to other designs are not detailed, the schematic itself serves as a foundational blueprint. Builders can adapt or modify the _power supply_ to suit their particular needs, such as integrating overcurrent protection or fine-tuning the output voltage with adjustable regulators. The straightforward presentation makes it accessible for those with basic electronics knowledge to assemble and troubleshoot.

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.

Presents a QRP AM/CW transmitter project specifically designed for the 10-meter band, utilizing a crystal oscillator and a collector-modulated AM oscillator. The design employs a 2N2219(A) transistor in a Colpitts configuration, generating 100 to 350 mW of RF output power depending on the 9-18 Volt supply voltage and modulation depth. Frequency stability is maintained by a 28 MHz crystal, with fine-tuning possible via a Ct1 trimmer capacitor for approximately 1 kHz adjustment. The resource details the RF oscillator stage, implemented with a 2N2219 NPN transistor, emphasizing frequency stability and low power dissipation. It also covers the amplitude modulation stage, managed by a 2N2905 PNP transistor, which impresses audio information onto the carrier. Selective components (C3, C4, C7, C5) enhance voice frequencies within a +/- 5 kHz bandwidth, and modulation depth is controlled by R2 and R3. The project includes a 3-element L-type narrow bandpass filter (Ct3, L3, C10) to suppress harmonics and ensure a clean output signal. The project provides a complete schematic diagram, a comprehensive parts list including specific capacitor, resistor, and inductor values, and construction notes for the coils (L1, L2, L3). It also offers practical advice on enclosure requirements, suggesting an all-metal case or a PVC box with graphite paint for RF shielding. Operational parameters such as current draw (27mA@9V to 45mA@16V) and input impedance (50 Ohms) are specified, alongside guidance on antenna matching and the importance of a valid amateur radio license for 10-meter band operation.

Sometimes many VHF-UHF modern transceivers have problems with BROADCAST Interference and CROSS-modulation from FM commercial broadcast stations this article shows a simple Batteworth HI-Pass VHF Filter to reduce this problem

Sherwood Engineering Inc. (SEI) offers a repository of technical presentations and white papers focused on optimizing amateur radio transceiver and receiver performance. Content includes detailed analyses of _roofing filters_, transmitted IMD, and receiver characteristics, with specific discussions on products like the Drake R-4C and Icom IC-781. Presentations from events such as Dayton Contest University (2008-2014) cover topics like "How To Optimize Rig Performance," "Transceiver Performance: 10 Years of Change," and "Choosing a Transceiver: Far from Simple." Additional white papers address HF mobile antenna efficiency, ground screen alternatives to buried radial systems, and common receiver problems with solutions. The site also provides historical product information for items like the SE-3 MK IV synchronous AM detector and various 455 kHz mechanical and crystal filters, though many products are no longer in production. Receiver test data and alignment tips for the R-4C are also available, offering insights into rig modifications and performance enhancements.

The Rock-Mite is a 40m CW kit offered by Small Wonder Labs . It features built-in keyer, direct conversion receiver with a crystal RF bandpass filter, 500 milliwatts of power, and switchable frequency offsets to work around QRM