Search results
Query: LF
Links: 623 | Categories: 7
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This web article details the construction of a 4-meter band coaxial dipole antenna, designed for operation between **70.000 MHz and 70.500 MHz**. The resource provides a bill of materials and step-by-step assembly instructions for a half-wave dipole constructed from _RG-58_ coaxial cable. The design specifies a direct 50 ohm feedpoint impedance, eliminating the need for an external matching network. Construction photographs illustrate the stripping and soldering processes for the coaxial cable elements, ensuring proper electrical connection and physical integrity. The article includes specific dimensions for the radiating elements, derived from calculations for the 70 MHz band. The project outlines the physical dimensions required for resonance at 70 MHz, with the outer braid forming one half and the inner conductor forming the other. The feedline connection is directly to the coaxial dipole's center, maintaining a 50 ohm characteristic impedance. While the article does not present SWR plots or VNA sweeps, it focuses on the mechanical construction and dimensional accuracy for achieving a functional 4-meter dipole. The design is intended for fixed station use, with no specific mention of polarization or height above ground, but implies a standard horizontal orientation for dipole operation. DXZone Focus: Web Article | 4m Coaxial Dipole | Construction Guide | 50 ohm Feed -
Two different ways to create autotransformer for end fed half wave wire antennas, by using ferrite or air core. -
1:49 UNUN using two stacked FT240-43 cores for end fed halfwave antenna. To match the end fed half wave antenna to the coaxial feeder, it is necessary to have a matching network or transmission line transformer. -
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A DC buss distribution box, make it yourself for less than $10 -
The radiating part is the vertical half of the dipole. You get nearly radiation in all directions, the second half must not be in 180°. The table below show how we get an impedance for direct feeding of 50Ohm coax. by DK7ZB -
The Hexbeam is a great little antenna! It should be high on your list of options if you want a design that can be multi-banded, exhibits useful gain and directivity, is very lightweight, has a small turning radius, and which lends itself readily to Do It Yourself construction. -
R3KBO is an amateur radio club producing and developing amateur radio kits and assembled products including HF VHF Power Amplifiers or RF Power Kits and amplifier parts, low pass filfers, band pass filters, sourge protections, splitters and combiners, antenna switches -
The Alpha-Delta group is a group dedicated 100% to DX Oncemetros in the band and can say that is 100% of Mexican origin. -
Just a single page describing my self as long some others interesting links. -
The Radio Operators Association of Dallas (ROADS) Club exist to promote interest in amateur radio communication and experimentation, fostering of education in electronic communications as it applies to amateur radio, development of individual efficiency, cooperation among members. and furtherance of the public welfare. -
G0HWC details and HTML files with images to build yourself a Ham Radio website. Get your Ham Web Site on the internet for free -
K1JJ presents a compilation of insights regarding vertical radial ground systems, specifically applied to 160m vertical arrays. The resource details 19 distinct observations and recommendations, emphasizing that ground radials primarily reduce ground losses rather than influencing pattern formation. It explains that RF current flows inefficiently through average soil, necessitating copper radials to create a low-resistance path back to the antenna base. The content suggests that **50-60 radials** are generally sufficient to achieve optimal efficiency, with diminishing returns beyond that number, and that radials should be laid on the surface for best performance. The discussion also addresses practical aspects such as wire gauge, installation techniques using 'U' shaped staples, and methods for connecting radials in multi-element arrays. It highlights the importance of radial length, stating that 1/4 wave radials are a crucial minimum, and that for 160m, radials should be at least _100 feet_ long. The resource critically examines the efficacy of elevated radials versus ground radials, noting that while a few elevated radials may suffice for VHF, HF applications, particularly on 160m, require extensive ground radial systems to efficiently collect RF currents in the near field. It also touches on the impact of radial systems on parasitic elements and the significance of symmetrical radial patterns for minimizing losses. Further practical advice includes wire type recommendations, proper soldering and weatherproofing techniques for radial connections, and considerations for integrating steel towers into the ground system. The author shares personal experience with installing 60 quarter-wave and half-wave radials under each of three in-line verticals, expressing satisfaction with the results. -
LA8W LN8W, Norwegian Contest Club -
This tutorial will teach you what you need to know so you can broadcast your live radio feed over the Internet yourself. -
A really simple project to make a power meter measuring RF output powers from a few mW up to half a watt. A DIY amateur radio project for QRP enthusiasts -
Pictures of Hellschreiber machines as projected by Rudolf Hell -
The life and times of development of a Linux D-Star repeater and dplus node. -
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How to home made antenna traps with material you can easily find, and how to properly tune it. -
MFSK is an easy-to-use chat mode for real-time amateur contacts, nets and bulletin transmissions, but not intended for contesting or Bulletin Board System (BBS) use. It is a half-duplex non-Automatic Repeat ReQuest (ARQ) forward-error-correcting (FEC) mode. It performs well on long-path fading conditions and in the presence of interference -
Jose B Rivera, N2LRB, shares his initial experiences with the Icom IC-7300, recounting a shift from skepticism to appreciation for the transceiver. He details how the radio's impressive Sherwood Engineering test results, ranking it #12, significantly influenced his decision, especially considering its competitive price point against higher-end options like the Elecraft K3s. The review highlights the IC-7300's strong receive capabilities, a key factor in N2LRB's purchasing decision, and notes the advantages of its SDR architecture for future updates. He describes the straightforward setup process, from unboxing and connecting PowerPole connectors to making a first contact with N0HQ, a special event station. N2LRB expresses satisfaction with the radio's clear audio and ease of tuning, even if the pan-adapter's utility for his operating style remains to be fully explored. He concludes that the IC-7300 offers exceptional value, providing SDR features and receive performance comparable to more expensive rigs at half the cost. -
The Milford Amateur Radio Club, Established in 1961 Milford, Michigan -
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. -
Low Band Receiving Antenna, it is a ground independent Receiving antenna which only needs two 10m support poles by DH1TW -
Litchfield County New Milford Connecticut Harwinton Warren Watertown Waterbury Washington -
Complete collection of the four main parts of this excellet research on modelling and designing half wave dipole antennas for 40 meters band, covering all aspects beginning from full wave length antennas, to shortened, loaded and reshaped dipoles -
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. -
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Selecting appropriate coaxial cable and wire for demanding amateur radio applications, particularly those involving high power or harsh environmental conditions, is crucial for maintaining signal integrity and operational safety. This resource details Harbour Industries' specialized offerings, which include Mil-Spec and commercial designs such as NEMA HP3/HP4 and SAE AS22759, suitable for aerospace, military, and industrial sectors. Their product line addresses the need for robust conductors capable of withstanding extreme temperatures and mechanical stress, often encountered in antenna systems or amplifier interconnections. The company highlights its AeroPOWER® Firezone M25038/3 cable, specifically engineered for high-temperature environments like aircraft engines. This particular product exemplifies their focus on solutions for critical infrastructure where reliability under adverse conditions is paramount. Such cables are relevant for hams building or maintaining stations in challenging climates or those operating high-power amplifiers where internal wiring must endure significant thermal loads. Harbour Industries also provides a range of high-performance cables designed to meet stringent specifications. Their expertise in high-temperature and high-performance cable manufacturing positions them as a supplier for specialized wiring needs beyond standard off-the-shelf options, ensuring durability and performance for advanced amateur radio setups. -
Personal homepage of DL4TA Ralf D. Kloth -
If you like building good antennas, this one is for you. The J-pole is a slim, omnidirectional, half-wave antenna fed at the end through a quarter-wave shorted transmission line. Its predecessor is the famous Zepp antenna developed for the Zeppelin airship. -
9M6MU Alfons details his family's efforts to establish an independent, self-sufficient home at Eagle Plateau in Borneo, a 50-acre highland property. The resource highlights their integration of **solar photovoltaic panels** for power generation, alongside managing water supplies, organic gardens, and fruit trees. It covers the practical challenges and rewards of living off-grid, including maintaining power generators and addressing infrastructure needs, all while pursuing the hobby of amateur radio. The narrative emphasizes a holistic approach to healthy living and nature conservation, reflecting the family's aspirations for an ideal ham world. Alfons and his XYL Doris share their experiences in building shelter and antenna farms, showcasing their dedication to independence and sustainable practices away from the conventional grid. The site also references the Hillview Gardens Amateur Radio Club, suggesting community involvement. -
The 2200-meter band (135.7-137.8 kHz) presents unique challenges for amateur radio operators due to its narrow 2.1 kHz bandwidth, low signal levels, and high noise. W1TAG explores various transmission modes suited for this demanding environment, highlighting that traditional voice modes like SSB and AM are impractical. Plain old CW serves as the baseline, demonstrating effectiveness across different modes, though signal-to-noise ratio (SNR) significantly limits practical speeds. The article notes that reducing CW speed below 5 WPM can improve copy, especially with computer-aided spectrum analysis software capable of decoding signals too weak for human ear reception. QRSS, or "CW sent slowly enough that speeds are best expressed in seconds per dot," is a key mode for LF work, with examples ranging from 3 seconds/dot to extreme 240 seconds/dot transmissions. _Argo_ by I2PHD is mentioned as a simple program for QRSS, enabling reception of signals like BRO, a Part 15 beacon, at a distance of **1100 miles**. Other modes discussed include Dual Frequency CW (DFCW), which uses frequency shifts to distinguish dots and dashes, and Binary Phase Shift Keying (BPSK), a phase modulation technique employing 0 to 180-degree phase flips. WOLF (Weak-signal Operation on Low Frequency), a specialized BPSK form by KK7KA, encodes 15-character messages into 960-bit packages, taking 96 seconds to transmit, and has demonstrated successful reception over **672 seconds** for a message from a 1-watt beacon. Further modes include PSK, FSK variations like JASON and MSK, and graphical modes such as Hellschreiber and Chirped Hell. The article concludes with a practical chart comparing the time required to send a simple message like "WD2XES FN42CH " across these diverse LF modes, offering valuable insights for operators planning contacts on the low bands. -
LA6EIA Ole's DX-blog details shortwave listening (SWL) and amateur radio DX operations from Norway, providing insights into propagation conditions and station reception. The blog frequently features specific reception reports, often including details such as frequency, mode, and signal strength, alongside observations of various broadcast and utility stations. It documents the author's personal experiences in chasing DX, offering a practical perspective on radio propagation and equipment performance. The content includes logs of received stations, sometimes accompanied by audio clips or screenshots of waterfall displays, illustrating successful decodes or strong signal captures. This resource presents a chronological record of DX achievements and challenges, reflecting the dynamic nature of radio propagation across different bands and times. The blog distinguishes itself by its focus on real-world SWL and amateur radio DXing from a Nordic QTH, offering a unique regional perspective on global radio phenomena. It serves as a personal journal of radio exploration, highlighting specific callsigns, frequencies, and operational details encountered during DX sessions. -
A trapped multi band end-fed-half-wave antenna for 40/30/20/17/15m. -
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The collinear antenna, or Marconi-Franklin antenna, is an omnidirectional, high-gain antenna composed of in-phase half-wave dipoles aligned vertically. By using quarter-wave transmission line segments, it maximizes gain at a low horizon angle, outperforming a half-wave dipole. Adding segments increases gain but narrows bandwidth. A popular DIY version, the CoCo antenna, uses half-wave coaxial cable segments connected by non-radiating transmission lines. Built with stable velocity factor cables, a matching quarter-wave sleeve balun, and ferrite rings for attenuation, the antenna achieves performance comparable to commercial models. -
Full article on how to build a home-made wire dipole antenna for 40 and 80 meters band. Article is fully in italian, as it was published on ARI RadioRivista, but is plenty of self explaining pictures that will guide you on homebrewing this trapped dipole antenna for the lower amateur radio bands. -
This antenna is designed for stations having a difficult time putting a decent signal on 160M from small or CC&R d lots. It is a 24.5 ft. vertical antenna, made from three 10 ft. PVC sections bolted together, and half wavelength of antenna wire helically wound around the PVC sections. -
Based in Stone Mountain Georgia -
Adapted from a similar project by NA4IT. Made with one quarter wave 2 meter radiating element pointing upward and it is surrounded by four 70 cm elements. -
Operating where independent media is suppressed, _Radio Free Europe/Radio Liberty_ (RFE/RL) delivers news and information in 27 languages to audiences in 23 countries. This resource primarily functions as a news portal, focusing on geopolitical events, regional conflicts, and human rights issues, particularly in areas like Ukraine, Russia, Iran, Afghanistan, and Central Asia. It features articles, videos, podcasts, and photo galleries, covering topics such as international relations, energy politics, and the impact of conflict on civilian populations, often highlighting the perspectives of local journalists and freelancers in challenging environments. The content frequently addresses the operational context of shortwave broadcasting, though the site itself is a digital news platform. For example, it details the implications of long-distance strikes and regional military capabilities, which are relevant to understanding the strategic importance of various communication methods. The resource also provides insights into the challenges faced by populations in areas with limited access to uncensored information, underscoring the role of independent news organizations in providing alternative narratives. -
The IZ3MEZ Web DX Cluster presents real-time amateur radio DX spots across 20 distinct frequency bands, spanning from **LF (2190m)** at 135.7 kHz up to **SHF (QO-100)** at 10499 MHz. It displays the DX callsign, frequency, DXCC entity, spotter callsign, and spotter DXCC entity, along with any accompanying comments. The cluster also lists various operating modes such as CW, RTTY, FT8, FT4, FT2, PSK, and SSTV, and supports special operating activities like QRP/P and specific award programs including IOTA, POTA, SOTA, WCA, and JOTA. The cluster's interface provides a dynamic feed of the latest 50 spots, continuously updated with precise timestamps. It offers direct **Telnet protocol** access for users preferring a command-line interface, with configuration instructions provided. The resource also integrates with other spotting networks like RBN and PSK Reporter, enhancing its utility for DXers and contesters seeking propagation information and activity monitoring across a broad spectrum of amateur radio frequencies. -
A very well done presentation about End-Fed Half-Wave antennas. This PDF document contains a summary of experiences in how to build custom EFHW antennas. Includes an interesting comparison table of UnUn configurations with recommended toroids, Wire size, turns and capacitors. An useful recap on common errors in building homebrew EFHW Ununs completes the document. -
In this article the author analyze six different type of VHF handheld antennas and as result of his self training on his new vector network analyzer published this interesting report
