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Theory of the classic Folded Dipole by G3TXQ

All antennas that are situated close to the ground are affected by that ground to some extent. This article explain effects and benefits of counterpoise.

A complete guide to magnetic loop antenna construction, with analysis of multi-turn and single-turn magneti loops, and and insight on choosing the optimal capacitor, or homebrewing your own butterfly capacitor

The page provides a project for an helical dipole for the 40 meters band, resonating on 7 MHz, created by PY1ZFK based on a design by DL8VO. It includes detailed instructions on building the antenna.

There are 2 possible TX extensions on the E version, either full TX (1.705 - 30 MHz) or just open up 5 MHz (cut the R968 jumper and make it into a K version). This mod has been tested on TS 590S and not on TS 590SG

Intended for portable long-term usage and also good for Field Day Events article by By Steve KB1DIG & Kim KB1GTR

A Variable Base-Loading-Coil for use under a HF Mobile Whip

This article is designed to be an introduction to the terms and basic mechanics of propagation methods that are to be found on the HF and VHF bands.

The skeleton slot antenna design was developed in the UK for TV use soon after WW2. This document describe and adapted version for the 2 meter band

Meter capable of accurately measuring low levels of RF power

A two meter Quad antenna project with detailed instructions on how to adjust the Quad gamma match

Hamlib is a library aid for software developers wishing to incorporate control of amateur radio hardware into their programs. Hamlib will allow ham radio software authors to concentrate on the user interface and the basic function of the program rather than radio control.

An Experimental, High-efficiency, Graphic-Tunable Magnetic Loop antenna and loop controller in a 52 pages PDF presentation with drawings and pictures

A Moxon rectangle antenna for 2 meters

All about Chilean contest, awards, links and general news and DX from Chile

Calculating HF helical whip antenna for mobile or portable operation

Associazione Radioamatori Italiani

Lights on why 160 meters is so unpredictable and what is being done to reveal its secrets

An amateur radio contest log sheet printable in A4 format, useful for portable operations, free to download PDF File.

A homemade tunable bandpass filter for all HF bands from 160m to 10m

Guide to ground mounting antennas, notes on efficiency, elevated installations, metal towers and masts, other mounting schemas, moble homes and rv, lightning protections, artiche by Bencher

A fractional bandwidth of up to 30:1 characterizes spiral antennas, making them highly effective across a very wide frequency range, often from 1 GHz to 30 GHz. The resource details two primary types: the **Log-Periodic Spiral Antenna** and the **Archimedean Spiral Antenna**, defining each with specific polar functions and illustrating their planar configurations. It explains that spiral antennas are typically circularly polarized, with a Half-Power Beamwidth (HPBW) of approximately 70-90 degrees, and a peak radiation direction perpendicular to the spiral plane. The content elaborates on critical design parameters affecting radiation, including the total length (outer radius) for lowest frequency, the flare rate ('a' constant) for optimal radiation versus capacitive behavior, the feed structure (often an infinite balun) for high-frequency operation, and the number of turns (typically 1.5 to 3 turns). It also discusses the theoretical impedance of 188 Ohms for Log-Periodic spirals, derived from Babinet's Principle, noting actual impedances are often 100-150 Ohms. The article presents a simple construction method for an Archimedean spiral, demonstrating VSWR and efficiency measurements. Measurements from a constructed spiral antenna show a VSWR that is fairly constant across the band, albeit with a mismatch loss of about 3 dB. The antenna efficiency remains around -5 dB (31.6%) across its operating range, indicating a decent wideband radiator despite opportunities for optimization.

The design and feeding of driven elements for VHF/UHF Yagi antennas , modeling, observations and some case studies by Graham Daubney F/G8MBI

XLS file with technical specifications about ham radio transceivers

As the sunspots return and DX propagation conditions to improve, the age old problem with QRM begins to show up on the amateur bands. Thif filter help you on improving reception

This article compares two commercial vertical antennas for the 4-meter amateur radio band: the Watson WVB-70 half-wave and the Sirio CX4-71. The Watson measures 2.03m in length, costs around £40, and exhibited adequate performance but required additional waterproofing after rain affected its VSWR readings. The longer Sirio CX4-71 (3.02m) performed noticeably better, delivering signals approximately 2 S-points stronger than the Watson. The Sirio demonstrated high build quality, a stable 1.2-1.4:1 VSWR, and weather resilience, though minor VSWR fluctuations were observed during rain and frost. Both antennas are half-wave designs requiring no ground plane radials.

This document details the design and construction of the PA70H, a 50-watt RF amplifier for the 70MHz (4-meter) amateur radio band. Built around the Mitsubishi RD70HVF1 MOSFET transistor, the amplifier delivers 45-55W output with 3-5W input power while operating on 13.8V DC at approximately 7-8A. The PCB design incorporates multiple protection circuits including overcurrent, SWR, and temperature control. The amplifier features various control modes including GND PTT, +13.8V PTT, and RF VOX. Two versions are available: PA70HLI (requiring 100mW input with additional driver) and PA70H (for 3-5W input). The comprehensive documentation includes circuit diagrams, assembly instructions, and performance data showing successful operation from both 100mW and 3.5W input sources.

Using the Raspberry Pi to operate Weak Signal Propagation Reporter

5-element antenna, with which G0JJL has worked lots of EU crossband, and won the RSGB Christmas Cumulatives 70MHz section twice in a row.

This PDF document details the construction of a **70 MHz** Big Wheel antenna, a horizontally polarized omnidirectional array. The design utilizes three full-wave loops, each approximately **2160 mm** in diameter, arranged in a triangular configuration. The resource provides mechanical dimensions for the antenna elements and a comprehensive bill of materials, specifying component quantities and types, such as M8 stainless steel bolts, 15x15x1.5 mm square aluminum tubing for spacers, and 8 mm aluminum rod for the arcs. The central hub is constructed from two 160x160x8 mm aluminum plates, with four 40 mm long polyamide insulators supporting the radiating elements. The feed system incorporates a 50 mm diameter aluminum pipe for mounting and a matching stub constructed from a 120x20x2 mm aluminum sheet, connected via M8x10 mm bolts. The resource includes a diagram illustrating the mechanical dimensions and assembly points, including the N-connector fixing point and the center conductor attachment. The project was published on May 25, 2011, by Peter OE5MPL and Rudi OE5VRL. DXZone Focus: PDF | 70 MHz Big Wheel | Mechanical Dimensions | **2160 mm** loop diameter

A PDF File of a Maria Maluca multiband HF antenna with schematic diagram, dimension and plan

Homemade Loaded Coil Dipole ( w8010 diamond ) for 10, 15, 20, 40 and 80 meter

70 MHz jpole half wave antenna by G7OGQ and G8CVF

History of codes of the world, russian codes, visual codes, and al long collection of telegraph codes as used worlwide including the international morse code and the relative variations

The ZS6BKW multi-band antenna, an optimized variant of the classic G5RV, is presented with detailed construction and tuning instructions. This resource outlines the antenna's design principles, which were developed by _Brian Austin (G0GSF)_ using computer programs and Smith charts to achieve optimal dimensions. It provides specific guidance on calculating and adjusting the lengths of the radiators (L1) and the matching ladder line (L2), emphasizing the critical role of velocity factor (VF) in achieving resonance. The article includes a step-by-step procedure for empirically determining the VF of ladder line using an antenna analyzer, ensuring accurate physical lengths for the matching section. It details the tuning process for the radiators, offering practical tips for incremental adjustments to achieve the best SWR curve. The resource presents SWR measurement results obtained with an _AIM-4170C_ analyzer across multiple bands, alongside predicted SWR graphs from an AutoEZ model. It confirms successful contacts on 80, 40, 20, and 17 meters, including a **17-meter DX contact** to Italy. EZNEC and AutoEZ models for the ZS6BKW antenna, covering 80 through 6 meters, are provided for download, allowing further analysis and customization. The document specifies component details, such as the use of Wireman 554 ladder line and #14 AWG THHN copper wire, and discusses the antenna's performance characteristics, noting high SWR on 15 and 30 meters but successful tuning on 6 and 80 meters with an external tuner.

VE3BDB's personal page serves as a dedicated resource for members of the Radio Amateurs of Canada (RAC) residing in the Ontario South Region. Bob Cooke, VE3BDB, previously held the position of Director for this region, offering localized support and information pertinent to the RAC's activities and initiatives within Ontario South. The page likely covered regional news, events, and specific guidance for local hams, reflecting his role in facilitating communication and engagement among the amateur radio community in that area. While the page is no longer active and Bob Cooke has transitioned from his regional director role to RAC Vice President for Field Services, its original purpose was to centralize information for Ontario South hams. The content would have been tailored to address regional concerns, promote local ham radio activities, and provide updates relevant to RAC members in that specific geographic area, directing users to the main RAC website for current information.

Learn how to start using ham radio satellites for your DX contacts, PDF presentation by Dave Long

In this PDF article Zack Lau describe how to homebrew a four element yagi beam antenna for 50 MHz band, including how to build mounting blocks and tubing clamps to hold elements.

Mounting on Roof or at Ground Level? Why ground plane antenna works better at lower level.

The Packet Radio beginners guide to packet radio operating by Buck Rogers K4ABT

Radio Budapest is the external service of Hungarian Radio Company Limited, the public service broadcasting organisation.

A trap on the coaxial cable, also known as choke, helps to eliminate the sneaking of the reflected RF- energy to the shack. The trap can be made from the coaxial cable that feeds the antenna

Technical supplement with schematics of the Yaesu FT-2800M Yaesu Transceiver

Schematic diagram of the VLA 200 power amplifier by RM Italy

This web article by VK3BLG details the construction of an experimental 70cm (432 MHz) circularly polarized patch antenna, intended for satellite communication. The resource provides dimensions, feed point specifications, and impedance matching considerations for a single patch element, with discussion extending to array configurations for circular polarization. Construction involves a copper patch element on a dielectric substrate, fed via a coaxial cable. The design is based on information derived from AO-40 satellite antenna specifications, focusing on achieving circular polarization for satellite reception. The article includes specific dimensions for the patch and feed points, along with impedance values. Validation is implied through on-air satellite reception reports, with initial signal reports of **1 S-point above noise** for AO-40 beacons using a grid reflector, improving to **3-4 S-points above noise** with a 2-turn helical feed. The author references a _NanoVNA_ for impedance measurements and discusses the relationship between slot and dipole antennas in the context of patch design. DXZone Focus: Web Article | 70cm Patch Antenna | On-Air Satellite Reception | Circular Polarization

This is the official site of the Milan branch of A.R.I.

VHF Power amplifier VLA 200 english manual

A chart presenting the results of impedance measurements made on a variety of common-mode choke implementations across the frequency range 1MHz to 30MHz by G3TXQ

Round-Up of different HF Upconverters for RTLSDR by KF7LZE