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A keyed piezo beeper, connected to the microphone jack of a HT, appeared feasible as a ready-made MCW generator.

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

Build you own RF probe, measure the level of RF voltage present at a particular point.

An RF Probe project by N5ESE

This is an on-line rf attenuator calculator provided free in order to promote the FLEXI-BOX. Calculates the resistor values, attenuation, minimum attenuation, impedance, reflection coefficient, VSWR and return loss of a matching Pi attenuator

Notes on the Troubleshooting and Repair of Small Switchmode Power Supplies

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

Nuand id the maker of bladeRF - the USB 3.0 Superspeed Software Defined Radio, 300MHz - 3.8GHz RF frequency range Independent RX/TX 12-bit 40MSPS quadrature sampling

A very informative review of the Icom IC-7300 direct RF sampling transceiver, including audio samples, recordings and a comparison vs the Elecraft KX3

Yaesu FT-100D Active Interface for the Codan 9350 and Comet SB-15 Antennas

Demonstrates the complete design and development process for a **Low Noise Microwave Amplifier** (LNA), beginning with conceptual design and progressing through prototyping. The tutorial series covers the initial stages of a single-ended first gain stage, focusing on critical parameters such as noise figure, gain, and stability. It systematically details the theoretical underpinnings and practical considerations for achieving optimal performance in microwave frequency applications. This resource provides a structured approach to LNA construction, enabling radio amateurs and RF engineers to understand the iterative steps involved in realizing high-performance receive-side amplification. It offers insights into component selection, impedance matching networks, and the measurement techniques required to validate design specifications, particularly for **microwave** band operation where noise performance is paramount.

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.

How to homemade antenna to be used with a handheld on the aircraft band to locate noise sources

This Microphone comparison article summarizes the test results of two popular ham radio microphones the ElectroVoice RE27 and Heil PR781

The MC3423 can protect sensitive circuity from power supply transients or regulator failure when used with an external "Crowbar" SCR.

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

An introduction to RF mixes and their main characteristics, article with diagrams and illustrations by VA3IUL

Antenna design for Horn Antennas

Constructing a dip oscillator provides radio amateurs with a fundamental piece of test equipment for resonant circuit analysis. This particular design, adapted by VK3YE from a concept by _Drew Diamond VK3XU_, details a practical build using readily available components. The unit incorporates four plug-in coils, covering a frequency range from **2.6 MHz to 55 MHz**, mounted on 5-pin DIN plugs for versatility. A salvaged two-gang air dielectric variable capacitor, fitted with a vernier reduction drive, serves as the tuning mechanism, with the smaller gang optimizing bandspread at higher frequencies. In practical application, the dip oscillator is used by setting the meter needle to approximately two-thirds scale. When the instrument's coil is brought near a tuned circuit under test, a noticeable dip in the meter reading indicates resonance. This allows for precise measurement of resonant frequencies in antennas, filters, and other RF circuitry, proving invaluable for homebrewing and troubleshooting. The design emphasizes short wire runs for stable operation, particularly at the higher end of its operational range.

Converting the GN9120 Wireless Bluetooth Interface for Amateur Radio

An article that explain with simple concepts and basic theory the correct usage of antenna tuners. It covers some aspects of common questions newcomers have on what antenna tuners are for, and what antenna tuners will never do.

Receiving QRSS CW on your PC by G0MRF

This system demonstrates that no galvanic coupling to earth is needed for a proper RF earth grounding

A large table wit properties of popular coaxial cables

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.

VE3NEA presents a detailed account of designing and constructing a **helical filter** specifically for 144 MHz satellite reception, addressing severe SDR receiver overloading from nearby Land Mobile Radio Network signals between 141 MHz and 143 MHz. The author's experience with RTL-SDR, RSP1a, and Airspy Mini receivers demonstrated the necessity of a narrowband solution to enable reception in the 145.8-146 MHz range with only 3 MHz separation from strong interference. The resource delves into the theoretical underpinnings of helical resonators, drawing upon Anatol I. Zverev's "Handbook of filter synthesis." It explains the equivalent circuit of a two-resonator passband filter, highlighting the critical role of stray capacitance (C3) in determining the coupling coefficient (K) and emphasizing the importance of **critical coupling** (K=1) for optimal filter performance. Misconceptions regarding tap positions and impedance transformation are clarified, with tap placement shown to control resonator loading and the trade-off between bandwidth and losses. Construction details include sourcing materials like 1/4" copper tubing and PCB, precise assembly techniques, and the use of tuning screws for frequency and coupling adjustments. Measurements performed with a NanoVNA revealed discrepancies from initial Coil64 calculations, necessitating adjustments to helix turns and tap positions to achieve the desired 3.5 dB passband loss and 40-50 dB suppression of interference.

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.

Demonstrates the fundamental principles for connecting a personal computer to a ham radio transceiver, specifically for utilizing sound card-based digital mode software like those in the MM Hamsoft suite. It details the basic hardware setup, emphasizing the use of shielded leads and proper audio routing from the radio's output to the sound card's input, and from the sound card's output to the radio's microphone or data input. The resource highlights the critical need for transmit attenuation, suggesting a 100:1 voltage divider to prevent overdriving the transmitter's audio stage, and mentions the optional addition of ferrite beads and decoupling capacitors for RFI mitigation. The guide also points to external resources for more detailed pin-outs and interface schematics, such as a specific QSL.net page, and recommends consulting the help files within MM Hamsoft programs for interfacing specifics. It underscores that while the process is straightforward, understanding the audio level management and proper cabling is key to successful operation. The author, VE5KC, provides practical advice drawn from common issues encountered by operators setting up digital mode stations.

Converting the Jabra A210 Bluetooth Interface for Ham Radio

Rotatable Antenna with Phased Elements based on the orignal design concept of HB9CV antennas, is considered to have an higher gain than standard quad antennas. The Swiss Quad Antenna does not need any spreader or boom.

PS8RF beacon tx in 7.035 Mhz with 3 W

Amateur radio map of Italy with WW locators, provinces abbreviations and Call sign Prefixes, in a A3 size PDF file free to download, made available by IU3KJL Davide

Examines Radio Frequency Systems (RFS), a manufacturer specializing in high-performance cable solutions for diverse communication infrastructures. The company, with over 120 years of heritage, focuses on designing and producing robust, long-life connectivity systems, including _low loss foam dielectric RF cable_ and _premium radiating cable_. RFS's product range supports critical applications in cellular networks, microwave antenna systems, and specialized installations within buildings and tunnels. The resource highlights RFS's commitment to innovation, addressing emerging industry standards like _FRMCS_ for railway communication and advanced fiber solutions for data centers. It also details the company's manufacturing capabilities in Hannover, Germany, emphasizing the quality and reliability associated with _Made in Germany_ products. The content covers various connectivity landscapes, from urban solutions for connected cities to private 5G credentials and future plans. Specific product categories include _fiber, power & hybrid cable_, and _low loss high power air dielectric RF cable_, showcasing their broad portfolio for complex RF environments.

This site features Samuel M. Goldwasser's latest and greatest "Notes on the Troubleshooting and Repair of..." series of comprehensive repair guides for consumer electronics equipment and other household devices.

Europeam perspective on BPL PLC

A simple RF probe diagram

RF Samplers and demodulators

RFE/RL Kyrgyz Service

4 Stacked 4 element yagi for six meters band

The cable testing approaches discussed in this article gives an idea about the electrical characteristics of a coaxial cable. Velocity of Propagation, Characteristics Impedance, Return Loss Measurement and more

A PDF Presetation from the W0DXCC Forum on how to improve the performances of the popular Yaesu FT-2000 transceiver

W1WD review and reception performance test of the Elecraft K3 transceiver.

An excellent and comprehensive article on portable HF operations with attention on selecting proper equipment

This article will explain a few of the ways author use an external SDR and Linrad to enhance his K3 experience. Linrad is one of many available SDR receiver programs. The same could be done with any radio that lets you access its IF frequency output. Article from NCJ Nov Dec 2019

The short history of the SSN Smoothed Sunspot Number at Luxorion

An interesting rf coaxial switch project capable of handling 800-1500 W. This is a cheap home made RF coaxial switch in use by PA0FRI

Showcasing a diverse portfolio, RF Industries specializes in interconnect solutions crucial for modern communication infrastructure. Their product line encompasses a wide array of RF connectors, precision-engineered coaxial cables, and robust data cables, all designed to meet the rigorous demands of wireless and wireline telecom, data communications, and industrial applications. The company emphasizes its role in "Connecting the Next Generation" by providing foundational components for evolving network technologies. Their offerings extend beyond basic components to include comprehensive installation and test kits, alongside various adapters and wire harnesses. This focus ensures that their products not only perform reliably in the field but also integrate seamlessly into complex systems, supporting critical infrastructure. RF Industries' commitment to quality and innovation positions them as a key supplier for those building and maintaining advanced communication networks, from _5G deployments_ to industrial control systems, ensuring signal integrity and robust connectivity.

This amplifier uses two 60w Spectrian amplifier boards with the usual input and output hybrid coupler and combiner.

Official site of ARI Comitato Regionale Friuli Venezia Giulia