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Near Vertical Incidence Skywave (NVIS) and the 40 meter Novice Sub-band.

An end-fed halfwave antenna for 20 meters band with balun pictures and description by PD7MAA

Codec2, an open-source speech codec, targets low bit rate voice communication, specifically designed for digital radio applications operating within constrained bandwidths. The project focuses on achieving intelligible speech quality at data rates around 2400 bits per second, a critical parameter for efficient spectrum utilization in amateur radio. Its development addresses the need for robust voice transmission over channels where higher bit rate codecs would be impractical or inefficient. The resource details the technical specifications and implementation aspects of Codec2, including its underlying algorithms and performance characteristics. It provides insights into how the codec processes speech to achieve its low bit rate, outlining the various coding schemes and their impact on voice fidelity and error resilience. The information presented allows radio amateurs and developers to understand the codec's operational principles and its suitability for integration into custom digital communication systems. Applications for Codec2 extend to digital voice modes on HF and VHF bands, enabling more users to share limited spectrum resources. The project's open-source nature facilitates community contributions and widespread adoption, fostering innovation in digital amateur radio. It represents a significant effort to provide a freely available, high-performance speech coding solution for the amateur radio community.

January 1955 QST article by W5DQV about constructing a Cubical Quad antenna for 14MHz PDF File

Over 1,000 stations in approximately 60 countries were worked using this modified twin-lead folded dipole, demonstrating its effectiveness with just 4 watts on 20 meters. This design, adapted from an ARRL Handbook concept, eliminates the shorting strap found in traditional folded dipoles, simplifying construction while maintaining performance. It utilizes readily available 300-ohm TV antenna feeder ribbon, making it a cost-effective solution for radio amateurs. The antenna's robust construction allows it to handle up to 100 watts without issues, even without a **balun**. The inclusion of a variable trimmer capacitor at the stub provides flexibility for tuning across different frequencies within a band, a practical feature for operators using transceivers like the Icom 735. Formulas are provided to calculate the precise dimensions for any desired operating frequency, enabling customization for various **HF bands**.

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.

An Off-center-feed antenna that covers 80, 40, 20, 17, 15, 12, 10, and 6 meters

A magnetic loop antenna for 7 Mhz by ZL1BJQ

How to build your own beverage antenna for 80-160 meters band by K5ZD

A project for a home made 5 element yagi-uda antenna for 2 meters, covering 144-148 MHz band by N1BMX

Backpacking, boating or mountaintopping ? Invest your time and pack this novel directional gain antenna on your next expedition

Details Guglielmo Marconi's foundational contributions to radio communication, highlighting his 1898 Patent **7777** which introduced tuning circuits for independent simultaneous communications. Chronicles the historic transatlantic reception of the Morse code letter 'S' on December 12, 1901, from Poldhu, Cornwall, to St. John's, Newfoundland, a distance of over _3,500 kilometers_. The exhibit showcases early Marconi 10-inch spark transmitters, identical to those used on the _Titanic_, alongside Canadian Marconi crystal detector models. It also features high-end commercial receivers like the IP501, weighing **87 pounds** and originally priced at $595.00, demonstrating the robust construction and technological advancements of the era.

An home made Z-Match antenna tuner unit that cover all HF bands between 10 and 160 meters

5/8 vertical groundplane antenna for six meters band

3 Element reversable quad antenna for 40 meters band

This 40 meter Inverted V antenna was tested and tuned at a height of 35 feet and proved excellent results. The ends of the antenna are about 11 feet above the ground. Article and video available

This document details the design and construction of a Vinecom 6N4 dual-band Yagi antenna for the 50MHz (6-meter) and 70MHz (4-meter) amateur radio bands. The antenna features 9 total elements (4 elements for 50MHz, 5 elements for 70MHz) on a 4.236-meter aluminum boom. Computer simulations using MMANA software predict 7.21 dBd gain on both bands with front-to-back ratios of 16.01dB (6m) and 15.37dB (4m). The design uses 12.7mm diameter elements mounted on a 32mm square boom, weighing 5.7kg total. Practical measurements with an MFJ-269 analyzer confirmed good SWR performance across both bands after element length adjustments.

DF9CY experience on a vertical antenna for 40 meter band

The circuit described below will substantially reduce or completely eliminate interference from almost any local source whilst leaving the wanted signal relatively unaffected, even though it may be on the same frequencey by TREVOR, G3ZYY

A shortened 160 meters band antenna for hams who do not have 260 ft of space, based on a open-wire-fed short dipoole

A short dipole wire antenna for 40 meters band. It is a folded dipole that do not make use of coils and can be used either in horizontal or inverted V configuration

An attic antenna for 40 and 80 meters band by NS1W

The 9A3MR contest QTH rental provides a fully equipped amateur radio station for DXpeditions or radio holidays on Murter Island, Croatia. The station features a Drake TR7 transceiver and a 16-meter tower with a rotator, suitable for various HF operations. Accommodations include a four-room apartment and a studio apartment, both within 200 meters of the beach, offering amenities like parking and a barbeque area. This QTH is located in Jezera, a fishing village with local stores and restaurants within a five-minute walk. While Murter Island itself does not qualify for IOTA due to a bridge connection, the Kornati Islands National Park (IOTA EU-170) is only 10 nautical miles away, with daily tourist tours available. The Krka National Park is also accessible by car, approximately 25 km distant, providing additional recreational opportunities.

If you have space constraint at your QTH for a HF antenna, you can try contructing this HF magnetic loop antenna for 40-20 meters bands

You can make your own 2-meter "rubber duckies" that will likely perform much better than many commercial units.

Cheap UHF antenna plans for 2 meters and up including 421 1296 and 902 Mhz

The G5RV multiband HF antenna, designed by Louis Varney (G5RV) in 1946, is a popular compromise antenna offering good overall performance on most HF bands when paired with an external antenna tuner. The basic full-size G5RV measures 102 feet across the top for 80 through 10 meter operation and is fed at the center via a 34-foot low-loss feed-stub. This interaction between the radiating section and the feed-stub facilitates matching across 80-10 meters with a standard tuner, often eliminating the need for ladder line directly to the shack. The antenna's design center frequency is 14.150 MHz, configured as a 3/2-wave dipole on 20 meters, with its 102-foot length derived from long-wire antenna formulas. Construction details emphasize the matching section, which can be open wire, ladder line (window-type), or TV twin lead. Each type has a specific velocity factor (VF) affecting its physical length for an electrical half-wave on 14 MHz; for instance, open wire requires 33.7 feet (VF 0.97), ladder line 31.3 feet (VF 0.90), and TV twin lead 28.5 feet (VF 0.82). The article provides formulas for calculating these lengths and discusses the antenna's behavior on individual bands, from 3.5 MHz where it acts as a shortened dipole, to 28 MHz where it functions as two three-half-wave long-wire antennas fed in-phase. Practical construction notes include recommendations for vertical descent of the matching section, sealing the coax junction, providing strain relief, and winding a coaxial choke coil to mitigate common mode current. The resource also presents dimensions for double-size (204 ft) and half-size (51 ft) G5RV versions, along with their corresponding matching section lengths for various line types, making it a versatile reference for hams considering this classic wire antenna.

A trapped dipole antenna based on the orignal W3DZZ antenna design resonating on 80 40 20 15 10 meters

A well documented article about construction and analysis of a horizontally polarized halo antenna for 6 meters band by Dr. Carol F. Milazzo, KP4MD

Shortened vertical antenna for 40 meters band an homebrew project

Article on a 2 and 6 meters halo antennas that does not require a mast has a very low part count and can easily be built with a minimum of tools.

A bowtie antenna is a type of antenna that reputedly provides higher gain at lower radiation angles than a center-fed dipole antenna at heights considerably less than 1/2 wavelength above ground.

3d parts printed to build an EZ-Lindenblad 2 Meters LEO Sat antenna as designed from Anthony Monteiro

A simple center-fed dipole made just with a thin-wall PVC pipe, aluminum tape, and RG-8X coax

A vertical monoband antenna design that can work from 6 meters to 70 cm by F5ZV in French

Manufacturer of single band and multiband transceiver bandpass filters for HF. High pass filters, two radoi headphones mix and switch, 6 meter portable antenna, antenna remote switching and steering.

A home made yagi antenna featuring 6db forward gain and 22 Db front back

A project of a bobtail-curtain antenna for 10 MHz

The Quadlong antenna for the six meter band. This antenna feature a total gain of 6,4 dBd, F/B 21 dB and is also available in 70MHz version. Includes detailed pictures and plot diagrams.

Building a 2 metre 144MHz VHF Yagi beam antenna, designed for portable use.

Accurately determining an antenna's feedpoint impedance is crucial for optimal performance, especially when experimenting with new designs or making adjustments. While SWR meters provide basic information, a full complex impedance measurement reveals the resistive and reactive components, which are essential for proper matching. Modern antenna analyzers, like the _Palstar ZM30_ or MFJ259B, simplify this task, but measurements taken through a transmission line require careful interpretation due to impedance transformation. This resource details a calibration method to precisely account for the effects of the feedline. It explains how a transmission line can significantly alter the measured impedance, illustrating this phenomenon with a Smith Chart example where an 80m antenna's [22 + j6] Ohms feedpoint impedance transforms to [82 + j45] Ohms after a 10m line. The guide demonstrates using a transmission line calculator applet, such as the one by W9CF, to reverse this transformation. It outlines the process of calibrating a specific length of RG174 coax, showing how an initial 26ft estimate was refined to **25.85ft** to accurately predict a known 22 Ohm load, significantly improving accuracy over uncalibrated results.

A 21 MHz Four Square Beam Antenna This popular antenna for the lower bands, can also work well on 15 meters, QST Article

An homemade portable trapped dipole antenna for 40 and 80 meters band with an optional extension for the 20 meters.

DX_Central, a compact desktop application, provides amateur radio operators with critical propagation data by aggregating solar statistics and imagery from various authoritative sources. This includes real-time information from agencies like NOAA and NIST, offering insights into current space weather conditions that directly impact HF propagation. The software is designed for both Linux and Windows operating systems, making it accessible to a broad range of hams. It presents a concise overview of solar activity, which is essential for planning DX operations and understanding band openings and closures across the HF spectrum. Operators can utilize the displayed solar flux index, K-index, and other relevant parameters to make informed decisions regarding their operating times and target bands, optimizing their chances for successful long-distance contacts.

Extension to an existing fan dipole originally modeled for 40 20 and 6 meters. This modification will add 80 15 and 10 meter bands.

An end fed 20 meter half wave antenna

A moxon rectangle for 50 Mhz band

A Slinky-based doublet or loaded vertical QRP antenna tested for 40 meters band

This antenna analyzer measures complex impedance over the 1.6 - 33 MHz HF spectrum

An 80 meter band vertical loop antenna setup