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Details the construction of a **multiband vertical** antenna, specifically designed for stealth operation in a rented property, covering 80m, 60m, 40m, and 30m. The author, N3OX, leverages a 12m Spiderbeam telescoping fiberglass pole as the primary support, noting its sturdiness compared to typical fishing rods while remaining light enough for quick deployment and takedown. The radiating element is a 14 gauge Flex-Weave wire, attached to the pole's top with a rubber grommet, and fed by 27 bare 18 gauge radials spread across a 40-foot square backyard. N3OX describes the impedance matching solution, opting for custom-built L-networks over a remote tuner to enable fast bandswitching. Using an MFJ-259B and EZNEC modeling, base impedances were measured and component values calculated with G4FGQ's L_TUNER and SOLNOID_3 programs. The 80m coil is wound on a 3.5-inch PVC form, while the 30m, 40m, and 60m coils are air-wound, self-supporting #10 wire. Variable capacitors are incorporated for 40m and 30m shunt elements, with the 60m impedance matched by a series inductor. The project includes a **servo-controlled** homebrew band switch, utilizing a two-pole 12-position ceramic wafer switch for remote operation, addressing the limited 80m bandwidth. The entire matching network is housed in a weather-resistant shelter constructed from lumber and aluminum flashing. N3OX reports good DX results at 100W, estimating the total cost between $150 and $250, depending on existing parts.

Portable, and shortened with loading coils rotatable dipoles for 6 meters, 20 meters and multibands.

Dipole antennas, unique broadband antennas, trap dipole antennas, coils, accessories for HF radio

The Flower Pot Antenna project details a portable dual-band antenna primarily operating on 10 meters, with secondary resonance near the 30-meter band. Construction involves winding RG58 coaxial cable uniformly around a large plastic flower pot, approximately 70cm high with a 60cm top diameter. The design eliminates the need for radials, contributing to its compact and lightweight nature. Key construction steps include soldering the inner conductor to the shield at one end of the wound cable and connecting the wound cable's shield to the rig cable's inner conductor at the base. An LC network, comprising a variable capacitor (0-200pF) and an inductor (10 coils, 5cm diameter, 2mm wire), is inserted between the wound cable's inner conductor and the rig cable's shield. Tuning is performed with an antenna analyzer, adjusting cable length and the variable capacitor for optimal impedance on 10 meters. The antenna performs effectively when installed horizontally.

A few hours of fun with PVC and wire and you have got yourself a respectable road radiator. The antenna consists of little more than some PVC pipe topped by a RadioShack replacement whip antenna and a couple of coils made from a small roll of #14 house wire.

This page describes the loading coil (inductor) that W8WWV built for my center-loaded 160 meter band (1.83 MHz) vertical antenna.

A new and simple method for tuning traps. You need 2-3Watt of your TRX and two homemade coupling coils by DK7ZB

HF Ham Radio mobile operation antennas manufacturer, W6HIQ, HA5CMG, VE7BOC, HF mobile antennas, screwdriver antenna, coils and filters.

This page explains how to construct high-Q inductor coils.

Base and mobile antennas,custom ball mounts, single, double, triple coil antennas, flat coils.

This page lets you do calculations for single layer air cored coils using the solenoid formula

Building coils for a portable dipole using a novel method of winding coils with weedeater cord! By K4MMG

An inverted V antenna for 40-80 with loading coils. This antenna is a full size on 40 and a shortened 80 by KG0ZZ.

One specific challenge in the KazShack, operating Single Operator Two Radios (SO2R), involved sharing a K9AY receive antenna between two transceivers without direct RF connection or manual feedline swapping. The solution, detailed in this project, adapts the **W3LPL RX bandpass filter** design to split 160m and 80m signals, feeding them to separate radio inputs while maintaining isolation. This approach also addresses the issue of strong broadcast band interference from a nearby 50KW WPTF transmitter on 680kc. The construction utilizes T-50-3 toroids and NP0 ceramic capacitors, built in a "dead bug" style on copper clad board. Each band's filter coils are identical and resonated to the desired frequency using an MFJ-259 antenna analyzer. A single DPDT relay, controlled by a remote toggle switch mounted on an aluminum panel, facilitates quick band switching between radios, simplifying low-band operations. While some signal loss is noted, the expected lower noise levels from the receive antenna are anticipated to compensate, potentially reducing the need for constant volume adjustments during toggling between transmit and receive antennas.

Presents a construction project for a linear-loaded 40-meter rotatable dipole, detailing the design evolution from mid-element coils to 300-ohm twinlead loading. It covers material selection, including repurposed fishing poles and EMT conduit, and outlines the assembly process for the antenna elements and mounting plate. The resource provides specific measurements for element lengths and linear loading sections, along with SWR plots demonstrating the antenna's resonance at 7.035 MHz with a 1.1:1 SWR, and bandwidth up to 7.120 MHz below 2:1 SWR. The article documents the antenna's performance during various RTTY and CW contests, including the SARTG RTTY and SCC RTTY contests in August 2006, and the ARRL DX CW and CQWW WPX RTTY contests in February 2007. It reports successful operation at 500-1000W, noting improved performance after replacing a faulty coax cable. Specific DX contacts from British Columbia, including stations in Europe and South Africa, are listed, illustrating the antenna's capability despite its shortened length and relatively low height of 55 feet. The content highlights practical considerations such as weatherproofing the connections and supporting the fiberglass elements to prevent sagging. It also includes a brief comparison to an inverted-V at similar height and a ground-mounted vertical, noting the rotatable dipole's quieter reception. The author shares insights into the iterative design process and tuning adjustments made to achieve optimal resonance.

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

A 40/80 meters dipole made with two loading coils based on a project by IK1ZOY

Pictures of loading coils according to OK1FIG

Make your own loading coils for antenna projects using Caterpillar Grommet strips.

Build an effective dipole antenna that needs much less space by adding two loading coils. This online calculator tells you how.

Presents a QRP AM/CW transmitter project specifically designed for the 10-meter band, utilizing a crystal oscillator and a collector-modulated AM oscillator. The design employs a 2N2219(A) transistor in a Colpitts configuration, generating 100 to 350 mW of RF output power depending on the 9-18 Volt supply voltage and modulation depth. Frequency stability is maintained by a 28 MHz crystal, with fine-tuning possible via a Ct1 trimmer capacitor for approximately 1 kHz adjustment. The resource details the RF oscillator stage, implemented with a 2N2219 NPN transistor, emphasizing frequency stability and low power dissipation. It also covers the amplitude modulation stage, managed by a 2N2905 PNP transistor, which impresses audio information onto the carrier. Selective components (C3, C4, C7, C5) enhance voice frequencies within a +/- 5 kHz bandwidth, and modulation depth is controlled by R2 and R3. The project includes a 3-element L-type narrow bandpass filter (Ct3, L3, C10) to suppress harmonics and ensure a clean output signal. The project provides a complete schematic diagram, a comprehensive parts list including specific capacitor, resistor, and inductor values, and construction notes for the coils (L1, L2, L3). It also offers practical advice on enclosure requirements, suggesting an all-metal case or a PVC box with graphite paint for RF shielding. Operational parameters such as current draw (27mA@9V to 45mA@16V) and input impedance (50 Ohms) are specified, alongside guidance on antenna matching and the importance of a valid amateur radio license for 10-meter band operation.

A multi-band portable vertical antenna can be built with relatively ordinary components obtained from the local hardware store, including replaceable loading coils

This page allows you to calculate in the most accurate way high-Q inductor coils.

Distributor of aluminum and a manufacturer of finished aluminum products. Pierce Aluminum offers a diverse inventory and distributes a complete line of sheets, coils, plates, bars, structural shapes, tubes, pipes and extrusions in the most varied alloys and sizes possible

Understanding current in loading coils

Tips on winding wire coils used as inductive loads, traps, band-pass filters, are implemented in a number of amateur radio projects especially antenna projects

Skin effect and proximity effect on making coils with stranded wire. An interesting comparison on making coils.

Communication Coil, Inc. designs and produces custom, high reliability Filter Networks, RF Coils, Chokes, Inductors, Baluns, Toroids and Power Magnetics for communications

The NB6Zep Antenna, an electrically shortened 80-meter end-fed wire, addresses space constraints for low-band operation by integrating two loading coils into a 37-foot wire. This design, modeled with _EZNEC_, explores configurations like the quarter-wave sloper and inverted-L, with the latter providing a more vertical radiation pattern and practical backyard deployment. The resource details specific coil construction, recommending 21 uH coils made from _BW coil stock #3026_ or similar, and outlines wire segment lengths for optimal tuning. Performance analysis indicates a radiating efficiency of approximately 27% with good ground conductivity, resulting in a signal typically 3-4 dB down compared to a full-size quarter-wave vertical. The antenna exhibits a narrow bandwidth, around 50 kHz, due to its high Q, necessitating a tuner for broader band operation. Feedpoint impedance is low, with ground resistance playing a critical role in achieving a usable SWR. The article emphasizes the importance of an effective ground rod at the feedpoint for proper operation and tuning, suggesting an antenna analyzer for precise adjustments. It confirms the antenna's suitability for DX, citing successful contacts from Oregon to the East Coast and Hawaii on a 160-meter variant, making it a viable option for urban operators seeking low-angle radiation on 80 meters.

winding coils for construction project

Maker of filters, oscillators, cristals Coils, Toroidal Inductions, Solenoids, Bifilar wound Solenoids, Trifilar Solenoids and Transformers Located in Kansas City, Missouri

Originally eveloped by I1FLC, uses seven plug in coils covering 3.0 to 30Mhz in a Colpitts oscillator circuit.

Manufacturer of transformers, inductors coils and chokes. Custom winding, EMI / RFI Filters, Antenna Windings on ferrite rod, Antenna Winding on phenolic. Any antenna coil designs.

Coil Q Measurements - With a special focus on wet coils.

The program can be used to calculate inductors (coils) and their number of turns on ferrite cores, ferrite shells and air coils. These can be used for baluns, Ununs, bandpass filters, low pass filters, resonant circuits, and more. The technical specifications of the cores are already integrated in the program. Application is free and runs on Windows 32 bit versions only. To make it run on Windows 10 64 bit need to be unzipped in a single folder.

While intended mainly for antenna loading coils, this article also applies to other resonant systems, such as amplifier tank circuits.

A very popular method of making a short dipoles resonate at a given frequency. This type of antenna is suitable for single band, narrow bandwidth use.

Constructing a dip oscillator provides radio amateurs with a fundamental piece of test equipment for resonant circuit analysis. This particular design, adapted by VK3YE from a concept by _Drew Diamond VK3XU_, details a practical build using readily available components. The unit incorporates four plug-in coils, covering a frequency range from **2.6 MHz to 55 MHz**, mounted on 5-pin DIN plugs for versatility. A salvaged two-gang air dielectric variable capacitor, fitted with a vernier reduction drive, serves as the tuning mechanism, with the smaller gang optimizing bandspread at higher frequencies. In practical application, the dip oscillator is used by setting the meter needle to approximately two-thirds scale. When the instrument's coil is brought near a tuned circuit under test, a noticeable dip in the meter reading indicates resonance. This allows for precise measurement of resonant frequencies in antennas, filters, and other RF circuitry, proving invaluable for homebrewing and troubleshooting. The design emphasizes short wire runs for stable operation, particularly at the higher end of its operational range.

About experiments and measurements on loading coils using net standing wave current

A dual band dipole antenna for 40 and 80 meters band. Total lenght of 26 meters, foreseen two coils at aprox 11 meters distance from center feed.

The webpage discusses metal fatigue in antenna elements for radio amateurs, offering construction tips and techniques. It covers theory, tricks, and the use of baluns and coils.

Brugtgrej presents a Danish online classifieds platform specifically for amateur radio operators and electronics enthusiasts. The platform facilitates the buying and selling of used equipment, including transceivers like the Icom IC-7410, various components such as X'TAL FILTER FMT-15A and TRANSISTOR 2SC3019, and accessories like Sadelta microphone capsules and SMA to SMA extenders. Users can post free advertisements for items they wish to sell or acquire, covering categories beyond amateur radio, including antique radios, military radios, and radio tubes. The site lists active advertisements, with 3136 online ads and 167 online users at the time of analysis, indicating a dynamic marketplace. It also features a forum for community interaction, discussing topics like repeater rings on 1297 MHz and FT8 activity. The platform's structure supports both 'Sælges' (for sale) and 'Købes' (wanted) listings across its various sections. Specific items observed include a Miniwatt pentode 4689, various capacitors and coils, and general electronic components, demonstrating the breadth of offerings available to the amateur radio community.

Rewinding solenoid coils and how to article

Repairing a Cushcraft R7000 antenna featuring several problems, mostly concerning coils and the insulating parts of the antenna.

A small antenna for 50 MHz made with copper cable loading coils

Electronic Products Design Inc based in North Carolina, offers you custom design of transformers, coils, and telemetry control systems.

This article demonstrate how to build and mount a 40 meter loaded dipole using basic materials. This antenna reduce the overall length of an HF dipole through the use of loading coils.

A 60-foot available space, for example, might necessitate a shortened multiband dipole array to cover 80, 40, and 15 meters effectively. This resource details the construction of such an antenna, combining full-size and coil-loaded dipoles on a single feedline. It addresses the common challenge of fitting multiple HF bands into restricted physical footprints, providing practical guidance for hams with smaller backyards or portable operations. The core of the offering is an interactive calculator that determines required loading coil inductance and dipole lengths for various amateur bands from 160m to 10m. Users input their available space, and the tool provides dimensions, coil turns, and an efficiency rating (Good or Fair) based on the antenna's electrical length relative to a quarter-wavelength. It also suggests suitable _PVC_ pipe diameters for coil forms. The article further illustrates a center feed-point assembly using an 18-inch section of 2-inch _PVC_ pipe, detailing eye-bolt spacing and coaxial connector installation. It emphasizes the importance of adequate spacing between parallel dipoles and offers customization options for the feed-point, including the addition of a _Balun_ for improved feedline isolation.

The "DIY Telescopic-V Antenna £35" project showcases the creation of a budget-friendly, portable telescopic V-shaped antenna inspired by commercial designs. Using eBay-sourced telescopic whips and custom mounting solutions, the author documents their process, testing, and adaptations. Despite challenges like weather and missing tools, the antenna performed well across multiple bands, enabling successful QSOs. Future improvements include exploring loading coils and testing in better locations. The compact design offers versatility for amateur radio enthusiasts seeking an affordable and practical solution.

The PAC-12 Antenna, a multi-band portable vertical, is meticulously detailed in this construction article by James Bennett, _KA5DVS_. The design emphasizes ease of homebrewing using readily available components from local hardware stores, including replaceable loading coils. It outlines the preparation of the 72-inch telescoping whip (originally from Radio Shack, with an alternate source now provided by _Pacific Antenna_), the construction of the loading coils from PVC risers, and the fabrication of the aluminum rod base sections. Specific instructions cover threading aluminum rod with a _1/4-20 threading die_ and assembling the feedpoint insulator with a BNC connector, along with recommendations for radial deployment. KA5DVS, an avid traveler and QRP enthusiast, developed the PAC-12 to address the bulkiness of random wire setups and the limitations of commercial portable antennas like the Outbacker or SuperAntennas MP1. His goal was a lightweight, packable antenna that disassembles into 12-inch sections, achieving an assembled length of approximately 8 feet. The design strategically places the loading coil away from the base for improved efficiency. The PAC-12 notably placed first in efficiency compared to a quarter-wavelength wire vertical at the HFPack antenna shootout during the Pacificon conference in October 2001, demonstrating its practical performance for field operations. Appendix C showcases various _NJQRP Club_ members' PAC-12 constructions, including a 20m beam made with multiple PAC-12 elements.