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Inches and meters Javascript Wavelength Calculator allow to input a frequency in MHz and calculate wavelenght in several units considering also fractions of wavelenght and the velocity factor. Includes an usefull inch to meter converter

A squint at the world of LF This website was initially thrown together to provide ready availability to data being collected from the measurement of a transatlantic LF (Low Frequency) path.

Spectrum manufactures very high-performance, low-cost, GPS-disciplined time and frequency reference standards for industry, scientific, calibration, broadcast and amateur operators.

TS-850 is not much effective on AM since it does produce fairly clean audio, however while it does noticeably improve low-end frequency response

Article by W1TAG on operating modes used on low-banding. The 2200 meter band (135.7 - 137.8 kHz) is only 2.1 kHz wide, so voice work on SSB or AM is out. Find out the best modes on LF

The Doppler Effect allows the distance between a satellite transmitting from space and a radio receiver on the ground to be measured by observing how the frequency received from the satellite transmitter changes as the satellite approaches, passes overhead, and moves away.

High Frequency Expermental Beacon "WV". The Beacon operates on the frequency of 13.55567mhz. This Beacon is very low power. It operates under Part 15 of the FCC Rules and Regulations. It transmits with only 1.5 milliwatts of power

Examples of absorbtive low-pass filters in which the unwanted high-frequency energy is separated from the wanted output and then dissipated in matched resistors

Ham radio transmissions can interfere with television reception. This is called television interference, or ham radio TVI. Consumer adoption of cable television has significantly reduced ham radio TVI. But the introduction of IPTV, or television over phone systems, has brought ham radio TVI back, often with a vengeance. Here's why

Zplots is an Excel application that allows you to plot impedance and related data obtained from a variety of sources. You can plot on both an XY chart and a Smith chart as well as view the data in tabular format. The XY chart can be customized with your choice of trace lines. Frequency (in MHz) is always shown on the X axis.

Several national physics laboratories operate radio transmitters that broadcast a time code signal.

Welcome to our line of Low Frequency, Natural Radio Research, Broadcast, Marine and Shortwave products. Our evolving product line is the result of our dedicated research efforts primarily in the areas of LF, VLF, MF, and HF.

The antenna handles 250 watts and covers 40 through 10 meters, with an optional add on coil for 80 and 60 meters. The author in this pages includes an interesting video in which describes the antenna setup, and the importance of the shunting coil on lower bands like 40 and 80 meters. SWR curves diagrams are also included and demonstrate the influence on resonating frequency of the shunting coil.

Valon Technology designs and manufacturers low cost, reliable radio frequency products such as RF Synthesizer modules, RF Frequency Dividers and Phase Gain Detectors. Main markets are military/defense, test engineering, radio astronomy, research centers and universities

This guide explores different radio bands that hobbyists use to talk to each other worldwide. It explains how these bands work and what they're used for. From low-frequency to high-frequency bands, each has its own unique features for people who enjoy communicating through radios

Antenna Analyzer plus 500 is a multifunctional measuring instrument, very useful for amateur radio activity. Its size allows you to easily take it for relocation as well. Frequency range: 100KHz - 500MHz. Access directly via WiFi. Includes a dual-channel signal generator

A Shielded Low Frequency Loop Antenna, allows Simultaneous Transmission and Reception at the Same Site.

The Texas Slow Net meets daily at 7:45 PM local time, on 3570 KHz +/- QRM. TSN is a traffic handling training net. All stations licensed for the frequency are welcome to participate

The Precision VXO (PVXO) and its matching Crystal Test Fixture (CTF) were created to provide a low cost means of evaluating the characteristics of crystals and a means of measuring their series resonant frequency.

Passive Bandpass Filter online calculator and filter formulas. Active Inverting Op Amp Bandpass Filters, Active Noninverting Op Amp Bandpass Filter, just enter the Low ir High Cutoff Frequency

The Waterway Net, sponsored by the Waterway Radio and Cruising Club, is dedicated to enhancing amateur radio communications for recreational boaters. Meeting daily at 0745 ET on 7.268 MHz LSB, the net focuses on safety and weather updates, providing a vital link for live-aboards and cruising boats to stay connected with families and friends. Position Reports and Float Plans are essential components that ensure safety for offshore passage makers. Established in the early sixties, the Waterway Net is one of the longest-running nets in amateur radio history. Open to all amateur radio operators with a General class license or higher, it encourages participation without requiring WRCC membership. Newcomers are advised to listen initially to understand net procedures before checking in. In emergencies, FCC regulations allow anyone, licensed or not, to use any frequency to call for help, with the 20-meter frequency of 14.300 MHz available for emergency assistance approximately eighteen hours a day.

Online HF Communication prediction system provided by the Australian Governament Buerau of Metereology allow to predict usable frequency rage for radiocommunications between two stations allowing to specify frequency and date range. This tool allow calculation with different methods and algorithms

Just a simple signal generator based on ADF4351 module from fleebay allows you to generate one single frequency that can go up or down in 100Khz steps via two push buttons.

This article introduces an Arduino-based QRP CW Transceiver designed for lower HF bands. The journey begins with the Wotduino, evolving from a keyer to a multi-mode beacon. The development includes a QRP transmitter and culminates in a receiver inspired by Roy Lewallen design. The transceiver, controlled through a control bus features a signal path, modulation, filtering, and adjustable frequency settings. Despite initial testing intentions, successful QSOs on 80 and 40 meters showcase its functional capabilities.

This project revisits a minimalist software-defined radio (SDR) receiver built using a Raspberry Pi Pico, now optimized for simplicity and affordability. Designed for breadboard assembly with through-hole components, the receiver covers 0–30MHz, supporting CW, SSB, AM, and FM modes with an OLED display and spectrum scope. Key improvements include enhanced frequency accuracy, reduced op-amp saturation, and lower-cost components. Powered by three AAA batteries, it delivers standalone operation for global signal reception. Ideal for hobbyists, the design fosters experimentation and is documented with firmware and schematics available online.

Cavity is often required at a busy site to not only prevent its receiver from being overloaded by off-frequency signals, but also be a good neighbour and prevent low-level signals from your transmitter from getting into other users receivers - not to mention the preventing of those other signal from getting back into your transmitter to generate spurious signals in its own right.

A 70cm / 432 MHz Transverter Project transverter circuit is an electronic device that converts a radio signal from the 2 meter to the 70 centimeter band and vice versa, allowing a single transmitter/receiver to be used for both bands. It consists of an IF stage, local oscillator, frequency multiplier, and amplifier. The circuit must be designed for minimal signal loss, noise and intermodulation distortion.

This document details the construction, programming, and operation of a modular WSPR transmitter. The transmitter utilizes an ESP8266 NodeMCU, an SI5351 synthesizer with a TCXO for stability, and selectable low pass filters. Construction involves soldering headers, components, and assembling filter module. The ESP8266 is programmed via the Arduino IDE, requiring library installations and code modifications, including network credentials, callsign, and frequency . The transmitter is powered by USB or Vin terminals and its frequency is selected by jumpers and software settings. The document also covers FCC restrictions and how to use the WSPR network

This project introduces the Loggi, a hybrid antenna merging the wide frequency coverage of log-periodic dipole arrays (LPDA) with the high gain and front-to-back ratio (F/B) of Yagi antennas. Traditional LPDAs span broad frequencies with moderate gain and low VSWR, while Yagis provide high gain and F/B over narrow bands. By analyzing high-Tau LPDA designs, it was found they could nearly match the gain of VHF/UHF Yagis while maintaining excellent patterns, F/B, and front-to-rear ratios (F/R). Optimizing specific elements for target frequencies (e.g., 144.1 MHz) led to the Loggi, which uniquely features all driven elements without passive directors or reflectors. This design effectively functions as a narrowband optimized LPDA, with front elements acting like Yagi directors and rear elements like Yagi reflectors, thus enhancing gain and directional characteristics while retaining broad frequency versatility.

The 8m ISM band, a unique frequency range between 10m and 6m, holds potential for amateur radio enthusiasts, yet it remains largely unallocated. This spectrum offers fertile ground for research and self-training. The author's experience with low-power transmissions and WSPR testing highlights the band's capabilities and the need for a narrow, speech-free amateur allocation to encourage experimentation. Discover the world of 8m ISM radio exploration and its future possibilities.

The Dipole Bazooka Antenna for 40 meters is a popular choice among amateur radio operators. Its design allows for easy construction using materials like RG58 coaxial cable and PVC. Measurements are calculated using specific formulas; for instance, at a frequency of 7,100 MHz, the total length is approximately 19.74 meters. This antenna offers a performance range of 97% to 99%, with an impedance of 49 to 52 ohms. Additionally, it can handle up to 1 kW of power and requires no modifications for connection.

During radio's early days, high frequencies were under 30 MHz due to technical limitations. As understanding grew, components improved, allowing for higher frequencies like VHF and UHF up to 3 GHz. The HF band's long wavelengths provide unique propagation challenges influenced by solar activity. VHF and UHF bands face diffraction and reflection issues but offer diverse applications, from amateur radio to 5G and GPS technologies.

This article focus on the radiation angle of vertical antennas and the fundamentals of electromagnetic wave propagation. The calculation of antenna length at 145 MHz is followed by an explanation of electromagnetic wave speed and the link between wavelength, frequency, and velocity. Author discusses the 5/8th wave vertical antenna, namely its performance and the influence of radiation angle on signal transmission. Figures and analogies demonstrate how different antenna types produce distinct radiation patterns. This highlights the importance of selecting the right antenna for a certain purpose, such as local traffic or dxing. The article discusses a variety of factors that affect antenna performance, including SWR, propagation conditions, and equipment dependability

This article explores the nuanced design challenges of Band Pass Filters (BPF) in radio receivers, balancing low insertion loss, high stop band rejection, and narrow bandwidth. The focus is on the "Series-Trap, Shunt-C" topology, resonator count impact, and meticulous layout design for superior stop band performance across various frequency bands

The recognition of telegraphy masked by noise at 40 and 80 signs/min telegraphy speed was studied in 10 normal-hearing subjects at different sound pressure levels (25-85 dB SPL in steps of 5 dB) as well as at different test frequencies (2000, 1000, 800, 630, 500 and 250 Hz). The ability to recognize the signs varied with varying SPL. Recognition for most of the subjects was best at an SPL close to 70 dB. All subjects improved their recognition as the frequency was lowered to 500 Hz, some even at 250 Hz. These facts should be taken into consideration when training telegraphy operators as well as in the construction of radio receivers to permit listening at low frequencies. Furthermore, the critical ratio was calculated at the different test frequencies.

The CAT (Computer Aided Transceiver) System in the FT-950 transceiver provides control of frequency, VFO, memory, and other settings such as dual-channel memo- ries and diversity reception using an external personal computer. This allows multiple control operations to be fully automated as single mouse clicks or keystroke op- erations on the computer keyboard.

Horn Antenna - The energy of the beam when slowly transform into radiation, the losses are reduced and the focussing of the beam improves. A Horn antenna may be considered as a flared out wave guide, by which the directivity is improved and the diffraction is reduced. One of the first horn antennas was constructed in 1897 by Bengali-Indian radio researcher Jagadish Chandra Bose in his pioneering experiments with microwaves. The modern horn antenna was invented independently in 1938 by Wilmer Barrow and G. C. Southworth. This Horn model antenna is suitable employed in the UHF or SHF radio bands. Making this horn model antenna it will be easy for a beginner to make if it works in the 10GHz frequency, because small dimensions so it is not so difficult and also offers gain up to 25dBi.

Learn how to design a Hentenna antenna, a portable asymmetrical double-loop antenna ideal for amateur HF or VHF bands. This page provides details on constructing and optimizing the antenna for maximum performance in DX communications. Discover how altering the antenna's vertical feed section can adjust the VSWR resonant frequency and how changing the support pole's position can alter the beam direction. Originally developed by Japanese 6-meter operators, the 'Hentenna' offers a unique design that allows for horizontal polarization when vertically oriented. Explore radiation patterns, VSWR charts, and antenna currents diagrams to optimize your antenna's performance for long-distance contacts.

The Morse Code Translator allows anyone to easily convert text into Morse code and vice versa. Simply enter the text to translate or Morse code to decode. This tool is useful for amateur radio operators, scouts, educators, or anyone interested in learning Morse code for educational, professional, or recreational purposes. Discover hidden messages, learn the Morse code alphabet, and practice decoding signals. The tool offers advanced options like adjusting frequency, words per minute, characters, and spacing. Experience Morse code visually with the light translator. Explore the history and uses of Morse code, from military and emergency communications to fun secret messages among friends.

When new to the 2-meter FM transceiver, securing a quiet frequency for chatter seems straightforward, but it's essential to navigate FCC rules and band plans effectively. Even though frequency allocations are consistent above 50 MHz for Technician licenses, adherence to specific segments within the 2m band—ranging from 144 MHz to 148 MHz—is crucial. This includes respecting designations for different modes like CW, SSB, and FM to prevent interference, particularly with satellites and exotic modes like EME. Understanding and following the structured band plans not only ensures legal compliance but also optimizes frequency use and minimizes disruptions in the amateur radio community.

Learn how LoRa mode can be used for APRS and connected mode packet radio, offering low power and long-range communication. Discover the growing popularity of LoRa-only APRS devices and the use of LoRa boards from manufacturers like Lilygo, Heltec, and RAK. Find out about firmware options like Ricardo Guzman's CA2RXU firmware, which incorporates previous work and offers KISS for external APRS clients. Explore LoRa APRS frequency and modulation settings in the UK, and consider adding CA2RXU firmware to lora-aprs.live for more radio-specific information. Dive into the world of LoRa technology for ham radio operators and experiment with different firmware options.

This article describes an HF upconverter for the FunCube Dongle Pro. Designed for radio amateurs, the converter extends reception capabilities to lower frequencies (0 Hz to 30 MHz) by mixing them with a higher oscillator frequency (100 MHz). This translates the desired signal into a range detectable by the FunCube Dongle (64 to 1,700 MHz). Key components include a double-balanced mixer and a low-pass filter to suppress unwanted signals. The project provides schematics, filter specifications, and design considerations for construction.

The multiband tuned doublet, or center-fed Zepp, is a simple and efficient HF antenna that operates effectively across most amateur bands using a balanced parallel-wire feedline and antenna tuner. Unlike coax-fed dipoles, it tolerates impedance mismatches with minimal loss. By selecting suitable feedline and dipole lengths, one can achieve stable multi-band operation. While it doesn’t match monoband Yagis, it offers excellent performance, low cost, and broad coverage. Its radiation pattern and efficiency vary with frequency, but it remains a practical and versatile solution for HF operators.

Icom IC-R75 tabletop HF communications receiver came onto the market back in 1999 and was taken out of production in late 2015. Frequency coverage is from 30 hz right to 60 MHz. This allows one to catch the 6 Meter amateur band as well.

KISS703 is a 703 Hz narrowband digital mode for amateur radio, designed for simple, low-power operation without computers. A 500 Hz pilot tone ensures frequency alignment, replaced by unique tones for 37 symbols (letters, numbers, space). Built from common discrete components, it draws about 40 mA at 12 V, ideal for SOTA/IOTA use. The receiver uses amplification, wave shaping, and a pulse-counting frequency meter for manual decoding via a calibrated meter. Transmitter and receiver calibration involves marking meter positions for each tone, enabling fully self-contained messaging with minimal hardware in portable or fixed operations.

This software enables remote monitoring of the Kenwood TS-590SG HF transceiver. Based on a lightweight, text-based monitor was developed using Python and ncurses. It connects via rigctld, displaying key metrics like frequency, power, SWR, and TX/RX state with minimal data usage. Ideal for low-bandwidth remote operation, it works over SSH or mobile data. The software is open-source under GPL v3.

This is a theoretical look at propagation on 630-Meters and 2200-Meters using ray tracing software. It expands on the brief discussion in the ARRL Handbooks. The Earth's magnetic field affects 630-Meter and 2200-Meter band propagation. Lower ionization reduces absorption, aiding low-frequency propagation. Differences exist between bands, limited daytime sky-wave propagation. Sunrise/sunset show promise, yet mechanisms are unclear. Ducting possible at night in specific conditions. Negative ions enhance propagation. Inefficient antennas and high man-made noise are anticipated. Groundwave propagation is significant on 2200-Meters.

This page provides instructions for unlocking additional frequency bands on your IC-7610 transceiver to access the 60m band. The step-by-step guide is useful for hams looking to expand their operating capabilities and communicate on this popular band. By following these instructions, you can ensure that your transceiver is set up correctly to operate within the regulations of the 60m band.

This PDF presentation explores using aircraft reflections for VHF communication. It explores the characteristics of reflected signals, including how they cause fading and vary in frequency due to aircraft movement. The feasibility of using such signals for communication is then examined. The presentation highlights challenges like requiring very narrow filters and strong frequency stability. It explores Slow-Feld, a slow version of Hellschreiber, as a potential modulation mode due to its tolerance for weak signals and frequency variations. While successful communication via aircraft reflections has been achieved, the data rate was slow and intermittent. The potential for communication over long distances, especially with busy air traffic, is discussed.

GDX is a free Linux DX Cluster client for Radio amateurs. It allows hamradio operators to connect to the Packet Radio DX Clusters network via telnet. Connection via radio frequency modem, or TNC, not available at the moment.