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Orbitron, a cardware application, provides robust satellite tracking capabilities for radio amateurs and visual observers alike. It leverages NORAD SGP4/SDP4 prediction models to accurately display satellite positions in real-time or simulation, accommodating up to 20,000 objects loaded from _TLE files_. The software includes an advanced search engine for satellite passes and _Iridium flares_, offering printable results for planning observations or QSO attempts. Sebastian Stoff's creation supports various visualization options, including a 'Nightlife' dark color scheme for nocturnal use, and integrates a database of cities and satellite frequencies. Users can synchronize their PC clock via NTP and update TLE data over HTTP, with ZIP support. The application also features rotor and radio control capabilities, either built-in or through user-defined drivers, which is particularly useful for automating antenna pointing during satellite passes. Its interface is designed for ease of use, making satellite tracking accessible even for beginners. First released in 2005, Orbitron 3.71 runs on Windows 9x/Me/2k/XP/2k3/Vista and can operate on Linux via _Wine emulation_, requiring minimal system resources. The software's precision relies on periodic TLE updates, especially for low-Earth orbit objects, to account for orbital decay and maneuvers by satellites like the ISS or Soyuz.

Facilitates reliable two-way communication under challenging propagation conditions, WSJT-X provides a suite of digital modes optimized for weak-signal operation across the amateur bands. These modes, including FT8, FT4, and Q65, are designed to decode signals significantly below the noise floor, enabling DX contacts, EME (Earth-Moon-Earth), and meteor scatter QSOs with modest station setups. The software supports various T/R sequence lengths and tone spacings, tailored for specific propagation phenomena and band characteristics, such as JT9 for MF/HF with **2 dB** greater sensitivity than JT65, and MSK144 for VHF meteor scatter. WSJT-X also integrates specialized tools like _MAP65_ for wideband EME reception with polarization matching to counter _Faraday rotation_, and QMAP for wideband Q65 reception with Earth-Moon-Earth Doppler correction. These companion programs extend the software's capabilities for advanced weak-signal work, particularly on VHF, UHF, and microwave frequencies. The project, maintained by Joe Taylor, K1JT, and the WSJT Development Team, is the official home and reference implementation for these weak-signal digital communication protocols. Recent releases, such as _WSJT-X 3.0.2_, introduce enhancements like the QMAP program, Q65 Pileup, and SuperFox mode, which offers approximately **+10 dB** system gain for Fox-and-Hound operations.

Earth view, with satellite data provided by The Living Earth.

Predicts ionospheric (sky-wave) propagation between any two locations on the earth on frequencies between 3 and 30 MHz

Online radio planning system, allow you to generate accurate radio frequency predictions for anywhere on earth

A 144 MHz kilowatt amplifier project details the construction and performance of a high-power VHF linear using the GU74b tetrode. This Russian tube, equivalent to the Svetlana 4CX800, is noted for its conservative datasheet ratings, performing closer to 800-1000W anode dissipation in practical applications. The design prioritizes compactness and achieves 1.2 kW output with only 20W of drive power, demonstrating a 70% efficiency at 2.5 kV plate voltage. The amplifier has been successfully deployed in demanding _EME_ (Earth-Moon-Earth) operations since June 1994. Challenges encountered during development included achieving stability with a grid-1 input configuration. The author, _CT1DMK_, opted not to publish the full design due to its complexity, suggesting it might be difficult for less experienced builders to replicate successfully. However, he invites direct contact for those with specific interest in the design. Future plans include a "144MHz GS35b compact amplifier" project, promising another kilowatt-plus design. This resource offers insights into high-power VHF amplifier construction and the practical application of specific power tubes.

Argo, developed by I2PHD and IK2CZL, functions as a specialized freeware viewer for various weak signal modes, specifically MTHELL, Slow CW, QRSS, and DFCW. It processes audio input to visualize and decode these extremely low-speed transmissions, which are often imperceptible to the human ear. The software's capabilities extend to EME (Earth-Moon-Earth) operations, where its sensitivity to weak signals is particularly advantageous for detecting faint lunar reflections. The application provides a visual representation of the received signals, allowing operators to discern patterns and decode information from signals buried deep within the noise floor. Its design focuses on extracting data from signals with very narrow bandwidths and long integration times, characteristic of QRSS and similar modes. This tool is distinctively useful for experimenters and DXers engaged in challenging weak signal communication, offering a dedicated platform for modes not typically supported by general-purpose digital mode software. Its specialized focus on _Slow CW_ and _MTHELL_ makes it a niche but effective utility for specific operating scenarios.

The K5OE 2-meter vertical mobile antenna design, detailed in this resource, employs a 3/8-wavelength vertical section complemented by four shortened radials, forming an off-center-fed vertical dipole. This configuration creates a self-contained lower half, enhancing efficiency compared to traditional 1/4-wave monopoles relying on vehicle bodies for a ground plane. The article specifies construction using PVC components, 10-gauge insulated wire for elements, and provides precise dimensions in both inches and centimeters for the 25-3/16" (64 cm) vertical and 7-3/16" (20 cm) radials. Performance data indicates an honest 3 dBi of gain at 6 feet elevation (2 dBi free-space), with a pattern favoring the horizon, suitable for Low Earth Orbit (LEO) satellite communications. At 20 feet high, the same antenna exhibits almost 6 dBi of gain, with a nominal 50 Ohm feedpoint impedance at 146.850 MHz. Tuning instructions involve trimming element lengths, with the author achieving a 1.2:1 SWR by pruning the mast to 24-3/4" and radials to 7". The resource highlights the antenna's effectiveness for mobile LEO satellite uplinks, particularly at low elevations, and its suitability for fixed, mobile, or portable operations. The flexible wire elements allow for easy folding, making it a practical choice for backpacking. The original design by K5OE was previously hosted on aol.com.

A 2-meter Turnstile antenna, detailed for amateur satellite communication, offers a straightforward build for those looking to engage with orbiting transponders. The author, WB8ERJ, shares his personal design and construction methods, emphasizing the antenna's simplicity and effectiveness for LEO (Low Earth Orbit) satellite work. This design provides a circularly polarized signal, crucial for mitigating _Faraday rotation_ and signal fading often encountered with linearly polarized antennas when tracking satellites. Construction involves readily available materials like PVC pipe and copper wire, making it an accessible project for many hams. The article includes practical advice on element spacing and feed point considerations, drawing from the author's hands-on experience in the shack and field. It highlights the antenna's utility for receiving signals from various amateur satellites, including the popular AO-91 and AO-92. The Turnstile's inherent omnidirectional pattern in the horizontal plane, combined with its circular polarization, yields consistent signal reception, often resulting in **stronger decodes** and **more reliable contacts** compared to basic dipoles or verticals.

SolarHam is a website all about the Sun and how it affects Earth. This site is routinely updated with breaking news, sometimes hours before other Space News websites. You can trust SolarHam.com for the most up to date and accurate solar information on the net. SolarHam is a trusted and easy-to-use website for anyone interested in solar activity and space weather. It gives daily updates on <b>solar flares</b>, sunspots, geomagnetic storms, and radio blackouts. The site uses data from NOAA and NASA to show what is happening on the Sun and how it may affect radio signals on Earth. Charts and images are clear, and reports are updated often. Many amateur radio operators use SolarHam.net to check band conditions and aurora forecasts before operating. The site is fast, well organized, and focused on the needs of the radio community. Whether you are a beginner or an experienced ham, SolarHam.net is a helpful tool for understanding space weather and its impact on radio communications.

MultiKeyer is a dedicated computer keying program designed for amateur radio operators engaging in specialized operating activities such as Earth-Moon-Earth (EME) and Meteor Scatter, as well as general contest operations. It provides distinct modes for both CW and Phone transmissions, enabling automated message sequencing and playback of pre-recorded audio files. The software's interface shares a similar "look and feel" to the popular WSJT Meteor Scatter/EME program, facilitating ease of use for operators familiar with that platform. For CW operations, MultiKeyer offers an EME Auto mode for sending timed messages crucial for EME and Meteor Scatter, alongside a Contest mode that handles automatic CQ calls and preprogrammed messages. On the Phone side, it features a Sequenced Phone mode for transmitting prerecorded .wav files during Meteor Scatter events and an Auto Phone mode for contest use. The program leverages serial COM ports for CW and PTT signaling, and the soundcard for .wav file playback, with configurable PTT interrupt options. MultiKeyer integrates with TRX-Manager for PTT and CW keying, and can send callsigns for logging. It also supports WSJT-style "callsign.txt" files for lookups and adheres to the SO2R protocol for parallel port connections. Designed for Windows 98 and NT, it generally functions on Windows 95, ME, XP, and 2000, requiring a 133 MHz Pentium-class processor.

BEAM_DX is a free windows software for radioamateurs or radio listeners usage. It allows to point a directionnal antenna towards an azimuth, a locator, an international prefix or any other geographical position on earth predefined by its latitude and its longitude

Presented here is a high-performance, circularly polarized omni-directional antenna that is easy to build, easy to tune, inexpensive, and will work all the mode J Low Earth Orbit (LEO) satellites

A quarter wave vertical end-fed antenna for the 40 meters band. As all vertical antennas, also this aerial requires a good earthing system. In this project the ground is composed by twelve 4, wires buried in the lawn by using a spade to create a slit to drop the wire into.

The Antenna Rotator Controller is unique in that it senses, displays, and controls to the earth's true magnetic field. The compass sensor, mounted in a waterproof enclosure, is attached to the mast and sends its signal to a microcontroller

Presents the detailed construction of the _FLA25HV_ antenna, a specialized array optimized for Earth-Moon-Earth (EME) communications on the 2-meter band. This resource provides schematics and practical insights into building a high-gain antenna system capable of reflecting signals off the lunar surface, a challenging but rewarding aspect of amateur radio. It covers the mechanical and electrical considerations essential for achieving the precise pointing and signal strength required for successful moonbounce contacts, often yielding **20 dB** or more gain. Amateur radio operators pursuing EME operations require robust antenna systems and precise tracking capabilities. The FLA25HV design addresses these needs by focusing on element spacing, impedance matching, and structural integrity to withstand environmental factors while maintaining critical alignment for lunar reflections. Such systems are crucial for making contacts over distances exceeding **768,000 km**. This personal page serves as a practical guide for hams interested in constructing their own EME arrays, offering a glimpse into the technical dedication involved in pushing the boundaries of VHF/UHF propagation.

Add-in module to Microsoft Excel, contains a set of radio amateur relevant special functions: DistSphericLocator(Loc1; Loc2) Calculates the spheric earth model distance between two locators [km] DirSphericLocator(Loc1; Loc2) Calculates the spheric earth model direction from Loc1 to Loc2

If you are interested in the environment, the weather and other natural phenomena then there is something magical about being able to see pictures of the earth from space just as it is right this minute. One way you can do this is by receiving images from weather satellites.

The ultimate Keyhole Markup Language (KML) plugin for Google earth. Keyhole Radio is a unique and powerful RF planning interface, accessed by loading a Keyhole Markup Language (KML) overlay in Google earth.

The Wireless Institute of Australia (WIA) provides an official directory and database of Australian amateur radio repeaters, detailing their locations, frequencies, and operational status. The resource includes downloadable files in PDF and CSV formats, along with a _Google Earth KMZ_ file for visualizing repeater sites across Australia, including Amateur, CB, and Marine repeaters. It also references external resources for various digital modes such as _IRLP_, _Echolink_, _D-STAR_, P25, Fusion, and DMR, providing links to their respective information sites. The WIA repeater data is cross-referenced with the _ACMA database_ to ensure accuracy, with updates typically occurring twice a year. The directory employs a color-coding system, where purple indicates repeaters carrying the WIA broadcast or callback channels, and a 'W' status denotes operational repeaters with the weekly WIA broadcast. The resource also outlines policies for removing unlicensed or non-operational repeaters from the PDF listing after specific timeframes, while retaining them in the CSV file for potential reinstatement.

Ballistic simulator "Orbit" allows the physical principles of the motion in the gravitational field of the Earth to be demonstrated and learned. You can calculate with this program the ballistic trajectories of the thrown bodies and orbits of spacecrafts and visualize the astroballistic situation on the flat map of the world and on the rotating globe in the real time

This online calculator computes the great circle distance between two points on the earth's surface

GW4ALG's _136 kHz Pages_ document the evolution of vertical antennas for the 2200m band, starting with a prototype mounted on a house wall. This initial design, despite achieving the first **395 km** GM-GW QSO, suffered from significant insulation breakdown, high RF losses due to proximity to the house, and difficult tuning adjustments. The author details the challenges of maintaining resonance and matching with a variometer in the loft, noting that adding three earth spikes offered no measurable improvement over a simple water tap connection. The subsequent experimental 12m vertical, relocated away from the house, significantly reduced dielectric losses and proved far more effective. This antenna enabled GW4ALG to set a world DX record on 136 kHz with a **1916 km** QSO to OH1TN, and an intra-UK record of **703 km** to GM3YXM/P. The resource further explores the use of helium-filled balloons to extend the vertical radiator, achieving heights up to 27m, typically 20m, for enhanced low-band performance. Practical advice on balloon types, inflation, and critical insulation between the wire and balloon is provided, emphasizing safety and avoiding arcing.

This simple modification is applicable to pretty much any 12 volt operated, positive earth equipment. by Chris Cox, N0UK, G4JEC

Distance and directions calculation program using both Spheric, the perfect round earth model, and Vincenty's inverse ellipsoid algorithm, the WGS 84 earth model.

JT65 is a digital protocol intended for Amateur Radio communication with extremely weak signals. It was designed to optimize Earth-Moon-Earth (EME) contacts on the VHF bands, and conforms efficiently to the established standards and procedures for such QSOs.

Improper grounding or earthing system can cause several unwanted RF interferences (RFI) to television sets, broadcast receivers, hi-fi sets and telephone sets. In this Article the author explain how to setup a proper radio shack grounding using coaxial cable and ceramic disc capacitor

Web based VHF-UHF RF planning powered by SPLAT! and Google Maps. Access via website, Android App or dynamic Google Earth interface.

Article about types of materials that make the best earth grounding systems

Presents a curated collection of newsletters dedicated to _Earth-Moon-Earth_ (EME) communications, primarily focusing on the 432 MHz band and higher microwave frequencies. The resource details various EME DX experiences and news contributions from operators like K2UYH (W6/PA0ZN), offering insights into successful moonbounce contacts and operational strategies. It serves as an archive of specialized content for those engaged in or interested in extreme weak-signal propagation via the moon. The newsletters provide practical information on achieving EME contacts, often including details on station setups, antenna arrays, and signal reports from challenging DX. For instance, operators might report achieving contacts over **750,000 km** round trip, demonstrating the feasibility of long-distance communication on UHF and microwave bands. The content differentiates itself by concentrating on the unique technical and operational aspects of EME, which contrasts significantly with terrestrial DXing, providing a specialized knowledge base for advanced amateur radio operators.

This resource details the four primary functions of a ground system: lightning energy dispersion, equipment safety, RF return path provision for end-fed antennas, and management of induced RF currents. It clarifies that a ground system's effectiveness varies depending on its specific function, noting that a good lightning ground might not be an effective RF ground. The content emphasizes that proper antenna system design, including baluns and appropriate feedline lengths, often negates the need for an RF station ground to mitigate common mode currents or RFI in the shack. The article quantifies lightning energy, stating its peak is in the dozens or hundreds of kilohertz, with damaging energy extending to hundreds of megahertz, and currents reaching thousands of amperes. It recommends solid, wide, smooth copper surfaces for ground leads to achieve low impedance across a wide frequency range. The author, W8JI, shares practical insights from his station, which includes two 300-ft towers and four 130-ft wire verticals, detailing his use of common point grounds and _DX Engineering RR-8 HD_ antenna switches for lightning protection without coaxial surge protectors. Specific examples of antenna systems prone to common mode current problems are listed, such as random wire antennas without proper feedline lengths and off-center fed dipoles. The text also explains how a ground screen or radial system can reduce local noise sensitivity for vertically polarized antennas by covering the lossy earth.

Free windows world map application display current time, sunrise and sunset, greyline map, dx stations, requires windows 7 or higher. The program includes three resized Natural Earth maps which have been resized to 4k or slightly less. By Simon Brown G4ELI better known as the inventor of Ham Radio Deluxe.

Building Eggbeater II Omni low Earth orbit satellite Antennas for 70cm by ZR6AIC

The GM4JJJ VHF and EME pages document David's extensive work in Earth-Moon-Earth (EME) communication, specifically on the 144 MHz band, and his involvement in amateur radio astronomy. The resource details his station setup and operational experiences, providing insights into the technical challenges and rewards of bouncing signals off the moon. It offers a glimpse into the specialized equipment and techniques required for successful EME contacts, a niche but highly rewarding aspect of amateur radio. David's content shares practical applications and field results from his EME endeavors, which can be particularly useful for hams contemplating or actively pursuing moonbounce operations. The information, while not a step-by-step guide, implicitly compares the complexities of EME with more conventional VHF/UHF operations, highlighting the significant power and antenna gain necessary to overcome path losses. This resource serves as a testament to the advanced capabilities achievable in amateur radio.

Guglielmo Marconi's foundational contributions to wireless communication began in 1894, inspired by Heinrich Hertz's discovery of radio waves in 1888. His initial experiments at his family home near Bologna quickly demonstrated signal transmission beyond line-of-sight, achieving distances up to **two miles** within a year. Marconi secured a patent in 1896, subsequently gaining interest from the British Admiralty after disinterest from the Italian government. By 1899, Marconi's system facilitated transmissions across the Bristol Channel (nine miles) and the English Channel (31 miles). A pivotal moment occurred in 1901 with the successful _transatlantic transmission_, defying the prevailing belief that Earth's curvature would limit practical range to approximately 200 miles. This achievement catalyzed the rapid development of the wireless industry. Marconi continued refining his inventions and, in 1909, shared the _Nobel Prize_ in physics with Karl Ferdinand Braun for their advancements in radio technology.

APRS web map with weather, telemetry, messaging and a bulletin board. Google Maps and Google Earth views update automatically in real time. 14 languages.

With the view to establish a quick and easy multi-band antenna deployment for portable and camping operations a simple long wire antenna with an earth or earth plus counterpoise arrangement with a 9:1 voltage unun including a tuner or simply with a tuner is one possible solution. With the 9:1 voltage unun and wire lengths suggested in the below tables the antenna should present non extreme impedances for all HF amateur band frequencies. This page is far from complete and represents the ongoing investigation into this type of antenna. Experiments to date seem to have raised more questions than obvious answers.

The early 20th century saw significant advancements in wireless communication, culminating in the first successful transatlantic radio signal. This historical account details Guglielmo Marconi's pioneering efforts, from his initial experiments with electromagnetic waves to his patented wireless system in 1900. It describes the technical challenges of long-distance radio transmission, particularly the prevailing belief that radio waves would be lost due to the Earth's curvature over vast distances. On December 12, 1901, Marconi established a receiving station in Newfoundland, Canada, utilizing a _coherer_ and balloons to elevate the antenna. Signals, consisting of the Morse code letter "S" (pip-pip-pip), were transmitted from Poldhu, Cornwall, England. The successful reception of these faint but distinct signals across **1,700 miles** confirmed Marconi's theories, marking an epoch in communication history. This achievement demonstrated the viability of global wireless communication, paving the way for future developments in radio technology.

The past and future of the Sun's solar cycle and possible impact on the Earth's climate.

In the VLF portion of the spectrum it is easy to listen to the emissions created by the Earth itself. These emissions are generated by many different mechanisms and are often beautiful to listen to. Coverage on LF and MF frequencies

Global manufacturer of Satellite Earth Station, Air Traffic Control Radar Antenna and High Frequency Antenna products for broadcast, government and enterprise satellite communication applications.

Site dedicated to amateur radio astronomy, providing information on Earth-Moon-Earth (EME) communication, the Search for Extra-Terrestrial Intelligence

This WebSDR, hosted at Goonhilly Earth Station in Cornwall, enables you to listen to the Qatar OSCAR-100 Narrow band transponder onboard the Es'hail-2 satellite.

The current, the voltage, the impedance, the bandwidth, the polarization, and how the earth influences the famous radiation pattern.

The ADIF Processor is an online application that visualizes amateur radio contacts from an ADIF log file using Google Earth. SOTA CSV log files can also be used. As well as allowing you to view and explore your contacts in Google Earth, you will be able to see a Markdown or text table of contacts, use the output ADIF file which contains QRZ.com data, accurate contact distances and fields populated from comments in the input file. Print QSL labels. One of the benefits of using the ADIF Processor before uploading/storing your ADIF file is detecting errors in callsigns and activity references (e.g. POTA or SOTA references).

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

Working low-earth orbit satellites from any place

Over 100 trained amateur radio operators comprise the New York City Amateur Radio Emergency Communications Service (_NYC-ARECS_), an auxiliary communications service dedicated to providing vital radio links during local, regional, or national civil emergencies. This organization supports governments, civil-preparedness, and relief agencies in situations such as power failures, explosions, fires, floods, earthquakes, or terrorist activities. Their operational readiness is critical for maintaining communications when conventional infrastructure fails, leveraging the resilience and adaptability of amateur radio. NYC-ARECS actively participates in the NYC Office of Emergency Management (_OEM_) Partners in Preparedness program and is a member of DHS FEMA's National Preparedness Coalition, demonstrating its integration into broader emergency response frameworks. The group's activities include regular training, maintaining operational readiness, and deploying communication assets across the five boroughs of New York City. Their efforts ensure robust, independent communication channels are available to support disaster relief and public safety operations.

The _Fuji-OSCAR 20_ (FO-20) amateur radio satellite, launched over six years prior, continues to operate reliably, despite a gradual decrease in its Nickel-Cadmium storage battery capacity and solar cell degradation. The satellite's power system can still supply approximately **10 W**, enabling operations. During the non-eclipse period, typically from mid-June through March, the satellite experiences a 0% eclipse rate, ensuring sufficient power generation. This allows for the potential operation of the onboard BBS, which had been previously suspended due to concerns about power shortages. An "eclipse rate" refers to the proportion of time a satellite spends in the Earth's shadow during each orbit. When the satellite's orbital plane is perpendicular to the sun's direction, the eclipse ratio becomes zero, meaning continuous solar illumination. Understanding these eclipse periods is crucial for managing satellite power budgets and scheduling operations, particularly for power-intensive functions like the BBS, which can now be considered for activation during periods of sustained solar exposure.

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