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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.

This antenna is very useful for receiving or scanning purposes, but you can use it for transmitting, too. It is 2,94m long and has a pi-configuration (Collins-Filter) for the matching.

An easy to make HF low pass filter form high power

Cluster monitor is a tool for web and telnet clusters monitoring. The program shows spot history, the latest spots are shown in a separate window with full information about the DX, announcements, WWV propagation, and full sorting and filtering capability. Full support for AALog and AAVoice by RZ4AG, DXAtlas by VE3NEA. Integrated dial-up support. Price USD 25

These inexpensive, easily built filters can be the buffer you need between the signals you want to hear and send and those you don't!

Amateur radio accessories, power supplies, tvi filters, speakers, microphones, swr meters, preamplifiers, switches, cable and connectors,

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.

AF Filter modification for the Yaesu FT-897D by Petr OK1FIG

Installing these filters is a big improvement in the quality of the rig of the Yaesu FT-897D

HF QSO/QSL/Award managment, ADIF Import/Export, full version free to everybody. Requires Access 97 or Access 2000 (with JPEG and TIFF filter installed), screen resolution 800x600/1024x768

The page provides detailed information on coax stub filters for multi-transmitter setups, including specific lengths for different bands and types of coax. It also references additional technical notes for further analysis.

It consists of a group of JavaScript driven web pages that are intended for use as a quick reference for Ham Radio operators or just anyone interested in electronics. Offer calculators for Resistors, capacitors, inductors, power supplies, filters, attenuators and antennas

Windipoles is a free passive real time filter simulator. Developed under Visual Studio .NET. No software installation required. Allows design, analysis, optimizations and plots, all graphically.

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.

RadioQTH's Vanity Calls service provides a utility for US amateur radio operators to locate available vanity callsigns, specifically focusing on the shortest possible options. The system filters through all potential callsigns within a user's license class and presents only those currently unused, with results weighted by either their actual character length or their equivalent length in _Morse code_. This approach assists hams in securing memorable and efficient callsigns for CW operation. The service also lists recently granted vanity callsigns, sorted by prefix, offering insight into current FCC assignments. It clarifies the common misconception that callsigns are granted on a first-come, first-served basis, explaining the random selection process for applications received on the same day. The platform updates frequently, providing current data on available 1x2, 2x1, 2x2, 1x3, and 2x3 callsign formats, which are highly sought after by _Extra Class_ and _Advanced Class_ licensees.

The I0JXX is an italian company that offers market their projects, also sells electronic products of high quality, both for Ham, both Broadcast and their accessories. VHF Antennas, mosfet power amplifiers, filters, insulators, power dividers, telescopic poles, antenna masts

Provide components to the amateur who wants to construct their own gear and to the professional who wants to save money and time in prototyping their circuit design, Filters, HF Amplifiers, Splitter Combiners, VHF Amplifiers, ATV

RDXCluster is a free windows telnet client for worldwide DX packet Cluster,featuring multiple spot windows, Band/Mode DXCC window, DX History window, Top DX window, Find, highlights, filters the spot by Roberto Verrini

CW keyers, Logikey, and antenna rotator controll like rotor-ez, and active audio low pass filters.

Band-pass filters can be critical components in competitive stations. This setup may help put your station on the map.

Antenna tuners, components, filters and baluns manufacturer based in germany

A Windows freeware DX cluster client, allows you to monitor DX spots from users worldwide includes DX filtering and statical functions.

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.

Active filter design software for windows, AktivFilter 3 for the design of active filters tuned on the opamp type.

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.

Live IOTA spots by the dxsummit dx cluster

QRZCQ.com provides a centralized online platform for amateur radio operators, integrating a global callsign database with DX Cluster functionality. The service features real-time DX spotting, filtering capabilities for specific bands (e.g., 160m, 80m, 40m, 20m, 15m, 10m), and specialized filters for awards like IOTA, SOTA, WWFF, and QRP activity. It also includes a logbook, QSL manager lookup, contest calendar, and various ham radio articles and news feeds, supporting a wide range of operating activities and information retrieval. The platform aggregates data from multiple sources, offering a dynamic view of on-air activity and callsign information. Users can register for free to access additional services, including a personal logbook, buddy lists, and chat features, fostering community interaction among over 198,600 registered users. The DX Cluster displays recent spots with frequency, DX call, spotter, and remarks, covering bands from VLF to VHF. Beyond DX spotting, the site provides resources such as repeater directories, propagation information, and a swapmeet, making it a multi-faceted tool for both casual browsing and serious DXing or contesting. The service also highlights active users, latest news, articles, and videos, keeping the content fresh and relevant.

A pdf file with schematics of an ssb and cw filter AF amplifier

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.

Simple inexpensive program that allows L-C filters designed by PCFILT or S/FILSYN which are to be built using air wound inductors and single layer capacitors cut from alumina or duroid substrate materials

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.

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

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.

We produce duplex filters for 6 m, 2 m, 70 cm, and 23 cm band but also for HF bands. Sella and produce products for Ham Radio Repeaters.

A graphics-intensive bandpass filter program based on the helical resonator.

Digital filter for Macintosh computers with a PowerPC processor

Free windows comprehensive tool for Finite Impulse Response (FIR) filter design

This web based application will compute circuit values required for an L-C circuit to resonate at given frequency. Also it will compute the resonant frequency if given values for L and C.

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.

This article presents a technical investigation into spurious emissions from the Yaesu FT-847 transceiver when operating on the 70MHz (4-meter) band. The author discovered significant problems with both factory "UK spec" and modified units. Spectrum analysis revealed that when transmitting at 70.2MHz, the radio produces numerous spurious signals, with the most prominent emission at 45.6MHz measuring only 3dB below the fundamental frequency. The study also documents poor power efficiency on 4m (10.3% at 30W output) compared to 6m operation (23.5% at 30W). Tests verified that jumper configurations had no effect on filter selection. The author warns that using these radios on 4m may violate license conditions due to excessive spurious emissions.

An home-brewed morse code CW filter with a central frequency of 800hz and a variable bandwidth from 230hz to 26hz by F5RDH in french.

Leading supplier of low and high frequency electronic filter design products for the design of wireless telecommunications equipment, semiconductors and more

Optimizing DX chasing efforts, this software provides a refined approach to monitoring the DXCluster. It allows operators to configure specific filtering criteria, ensuring that only relevant DX spots are displayed, thereby reducing clutter and focusing attention on desired entities or bands. The application integrates alarm functionalities, notifying the user when a spot matching their predefined parameters appears on the cluster, which is particularly useful for working rare DX or specific band slots. Spot supports both macOS and Windows operating systems, offering a cross-platform solution for a broad user base. Its design emphasizes user control over the displayed information, moving beyond a simple stream of cluster data to an actionable intelligence system for DXers. This client aims to streamline the process of identifying and pursuing DX opportunities. While the software was previously a commercial product, the developer, K3NC, has retired and made registration files for DXBase 2007 available for free, along with a utility to generate registration keys for that specific version. This allows continued use of the DXBase 2007 logging software, though it's important to note the 64-bit OS compatibility modification required for generated registration files.

TX RX Systems Inc. manufactures signal boosters, rf antennas, transmitter combiners, cell enhancers, land mobile radios, duplexers, receiver multicouplers, bidirectional amplifiers, bda, rf amplifiers, rf filters, rf cavity filters, rf combiners, rf components, in building rf coverage, repeaters, repeater amplifiers, rf management equipment, rf systems, and rf solutions. TX RX Delivers Reliable Solutions.

This is an interactive design package for designing analogue (i.e. hardware) filters made of inductors and capacitors (Ls and Cs).