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A Variable Base-Loading-Coil provides a practical solution for optimizing HF mobile whip performance across multiple bands. The design, as presented by VK4ADC, details a coil wound on a 50mm PVC former, utilizing 1.6mm enamelled copper wire for robust construction. This approach allows for precise tuning, a critical factor in achieving efficient radiation from a mobile setup, where antenna length is often compromised. My own field experience with similar base-loaded whips confirms the importance of a well-designed loading coil for maximizing signal strength and minimizing SWR. The VK4ADC design incorporates a sliding contact, enabling continuous adjustment, which is superior to fixed taps for fine-tuning resonance on the fly. This variable inductance allows the operator to quickly adapt the antenna to different HF segments, from 80 meters up to 10 meters, without needing to swap out multiple coils. The document includes specific winding data, such as the number of turns per inch and the overall length of the coil, which are essential for replication. It also touches upon the mechanical aspects of integrating the coil with a standard mobile whip, ensuring a stable and weather-resistant assembly for reliable operation during mobile DXing or casual rag-chewing.

A monster magnetic loop antenna for 160 meters band. This Magnetic loop is optimized for 1840 Khz + 50 Khz. PDF Article published on La Radiospecola 10.22

Italian web site describing a project for a 2 meters home made halo antenna

This modification will allow the use of separate receive and transmit antennas on the Kenwood TS-850S/AT.

The original project of a dual band yagi antenna for 50 and 70 mhz, published on dubus 2/2007 by YU7EF

Home made WiFi 11dBi, wide band antenna by T. Marshall

40/20/10 Meter Fan Dipole attic antenna article by KD2GOE

A magnetic loop antenna working from 30 to 15 meters with 100W

The SCOTIA Bandhopper, a multi-band mobile vertical antenna, offers a unique sliding coil design for rapid band changes across 10m to 80m. Drawing inspiration from the classic Webster _Bandspanner_, this design improves efficiency through near-center loading, theoretically achieving up to **2.25 times** greater radiation resistance than base-loaded counterparts. The antenna, extending to approximately 10 feet on 80m, utilizes a 5-foot fiberglass tube with an internal loading coil and a 57-inch tapered steel whip, allowing continuous tuning across bands without changing coils or whip sections. Field results from GM3VLB and the SCOTIA team, based on over 40 years of /M and /P operations, indicate the Bandhopper significantly outperforms shorter mobile whips. Its slim profile minimizes drag, making it suitable for sustained motorway speeds. The design incorporates a novel "fixed spring contact" arrangement for the variable inductance loading coil, with two sets of contacts for 10/12m and 15-80m. Construction details are provided, including materials like boundary marker poles and specific wire gauges, with an estimated build cost of **£20** or less, depending on junk box availability.

Operating on the 2200m band (135.7-137.8 kHz) often presents challenges for amateur radio transceivers, which typically exhibit poor receiver performance at these very low frequencies. This project addresses the issue by providing a design for a dedicated 137 kHz antenna preamplifier, specifically tailored to improve signal reception for radios such as the _Yaesu FT-817_. The preamplifier circuit utilizes a low-noise FET input stage, crucial for minimizing self-generated noise and maximizing the signal-to-noise ratio from weak LF signals. The design includes a detailed schematic, component values, and construction notes, enabling homebrewers to build a functional unit. The goal is to achieve significant gain, making the faint signals on 2200m more discernible and improving overall band usability. Key design considerations include impedance matching to typical antenna systems and ensuring stable operation across the narrow LF segment. The circuit aims for a **low noise figure** and sufficient amplification to overcome the inherent limitations of general-purpose HF transceivers when operating below **200 kHz**.

A ferrite antenna for Low Freqencies

Exagonal Beam antenna cover 20-17-15-10 meters By KE4NU

What is an EWE Antenna, comparisons, performance and homebrew plan

A Wire resonant loop antenna for 160 meters band article by N4KC

Experiments on HF antennas for restricted spaces. In this article author experiments antennas for 80-10 meters band having just a very small garden and several restrictions. Basic antennas consists of laded multiband dipoles and fan dipole antennas

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

A very efficient 80 meter Counterpoise antenna designed to reduce ground losses from inadequate radial systems beneath inverted L antennas, a project by DM2GM and DM4IM based on the original K2AV antenna concept.

A project of a small antenna, just 50 cm for the 7 MHz band. An EH Antenna plan for the 40 meters band

Operating an 80/40/20M fan dipole for DX is analyzed through EZNEC modeling, focusing on the antenna's performance in a real-world, low-height installation. The resource details the physical construction and SWR measurements of the fan dipole, comparing them against EZNEC simulations. It also incorporates High Frequency Terrain Analysis (HFTA) data to illustrate typical DX elevation angles for various regions from New England, providing a crucial context for evaluating antenna patterns. The analysis presents EZNEC-generated azimuth and elevation patterns for each band (80M, 40M, 20M) at specific frequencies, showing gain figures at different elevation angles relevant to DX propagation. It compares the modeled SWR with measured SWR, attributing discrepancies to coax attenuation. The study concludes with observations on the antenna's azimuth performance (omnidirectional within ±1.5 dB) and its less optimal elevation gain at desired DX angles, highlighting the impact of low antenna height on DX capabilities.

A 6 dB gain Moxon rectangle antenna, designed for the 2-meter band, offers an excellent solution for hams seeking a compact, directional antenna for **SSB** operation, particularly in restricted spaces like an attic. This design emphasizes ease of construction using readily available materials such as 4mm OD brass tubing and plywood, making it an accessible project for many radio amateurs. The antenna's inherent characteristics, including a high front-to-back ratio of 37 dB and a 50-ohm feed impedance, contribute to its effectiveness in mitigating local noise and focusing radiated power. The project leverages the free MoxGen program for precise dimension calculations based on the desired frequency and wire size, and utilizes 4nec2 for pattern analysis, confirming a 3 dB beamwidth of 80 degrees. Construction involves bending brass tubing for the driven and passive elements, mounting them on an 800 x 350 mm plywood boom, and securing them with cable clips and epoxy resin. Initial SWR measurements at 144.3 MHz showed 1.6:1, which improved to 1.3:1 at 145.3 MHz across a flat band from 144.1 MHz to 145.5 MHz after adding a **coaxial choke** to mitigate common mode current.

Demonstrates how to construct an automatic band decoder, moving beyond manual selector switches for antenna and filter control. It addresses the challenge of varying band data outputs from different transceivers: Icom rigs provide voltage values, Yaesu rigs use Binary Coded Decimal (BCD), and Kenwood rigs lack direct band data output. The resource highlights a clever solution utilizing logging software like _CT (K1EA)_ and _DX4WIN_ to emulate Yaesu's BCD output via a PC's printer port, making the decoder compatible with any rig. The author details experiences building decoders based on designs by Bob _K6XX_ and Guy _ON4AOI_, noting K6XX's simple TTL chip design and ON4AOI's more comprehensive, opto-isolated unit capable of controlling ten outputs and bandpass filters like the _Dunestar_. It also references a _W9XT_ board design, which Steve Wilson, G3VMW, modified with BD140 transistors for source drivers, emphasizing safety. The author successfully cased an ON4AOI-based decoder in an old modem case, connecting it to an FT1000MP or a PC printer port to drive remote relays and a Dunestar Band Pass Filter.

This calculator is designed to give the vertical length of a quarter-wave ground plane antenna, and the length of each of the four radials for the selected frequency you have entered

Microstrip Patch Antenna Calculator determines the length and width in millimeters of a rectangular patch antenna.

An extended double zepp antenna by F5ZV in french

This Z-Match is a link coupled all-band tuner. Two all band tank circuits cover 3-14mhz and 14-30mhz. The tank output links are selected with a very heavy duty SPDT rotary switch.

The GM3VLB Poor Man's Antenna Analyser

Demonstrates the construction and implementation of a **two-element phased vertical array** for 40 meters, utilizing _Christman phasing_ techniques. The author, W4NFR, details the process from building individual 1/4-wave aluminum verticals to integrating them into a phased system. The resource covers antenna spacing of 32 feet, elevated radial design, and the critical steps for tuning each vertical to achieve a 1.1:1 SWR before combining them. It also provides insights into calculating precise coax lengths for feedlines and the phasing delay line, emphasizing the use of an MFJ-269 Antenna Analyzer for verification. The finished system exhibits good front-to-back nulls, with an overall SWR ranging from 1.6:1 to 2.2:1, which is managed by an antenna tuner. The project includes detailed photos of the relay box, showing 12 VDC relays capable of handling 5KV, and the control box in the shack for switching between three different antenna pattern configurations. Static bleed-off chokes are incorporated for protection, and the construction emphasizes robust weatherproofing for outdoor elements.

Two Delta-Loops in phase. The purpose of this article is to propose an antenna with a high gain, a high efficiency and a very low price that is easy to build for any frequency.

Comprehensive information page about bi-directional Beverages, including applications, construction details, and tips.

Carry a small stock of new and reconditioned parts for both rotators and control boxes for the following makes: CDE/HYGAIN , YAESU , STOLLE.

A DIY guide to build your own compact multiband HF antenna based on the G3TXQ version using a 1:4 balun. This article includes the full part list and instructions to assembly, including the center plate.

This project details the construction of a **full-sized 40-meter vertical antenna**, born from a renewed interest in 7 MHz operation and a desire for improved effectiveness over simple dipoles. The author, K5DKZ, initially focused on VHF experimentation, which provided an inventory of aluminum tubing and fiberglass spreaders for this endeavor. Before this vertical, K5DKZ utilized an 80/40 meter inverted-vee trap dipole and a 40-meter broadband dipole, but now primarily uses a pair of full-sized, phased, quarter-wave verticals spaced 35 feet apart for serious 40-meter work. The construction involves a base-heavy design for stability, using a 44.5-inch section of 1-1/4 inch steel TV mast driven into 1-3/8 inch aluminum tubing, insulated by a 105-inch section of Schedule 40 PVC pipe. The assembly reaches 31 feet, close to the 32 feet required for a quarter-wavelength on 40 meters, with fine-tuning achieved by winding wire onto a fiberglass spreader. The design is explicitly presented as a foundation for a two-element 40-meter Yagi beam, outlining modifications like substituting aluminum for steel in the base and using an inductive hairpin match for the driven element. The article also discusses tuning considerations for a large 40-meter beam, noting the 100 to 200 kHz upward frequency shift when raised, and suggesting methods for installation on a tower. The author emphasizes the cost-effectiveness and good performance of the monopole approach, especially when multiple verticals are needed.

A wire dipole antenna for 80 meters band

The 2BCX Slim Jim by F.C. JUDD, G2BCX.

Two meter band antenna

The information in this article has come from many amateur sources, the most notable was from WA6TEY (sk 1985) Ray Frost, who was a pioneer of VHF Quad designs and one of the best Southern California Transmitter Hunters. Ray built hundreds two meter quads in single and paired configurations as well as his famous mobile radio direction finding quad.

Understanding Amateur Radio NVIS Antennas and Propagation

Here is a review of the 40 and 80 meter band Double Bazooka antennas as used on the HF shortwave bands.

G0KYA review of the EH antenna for 20 meters band

VE3CVG 222 MHz (1.25m) 6 element plumber's delight yagi antenna

A page by 9A7PJT dedicated to HB9CV yagi antennas includes link to the HB9CV calculator program and some interesting plans

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 Gizmotchy high performance horizontal and vertical beam antenna for 2/6/10/11 meter bands

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

The Remote Control Antenna Switch consists of two circuit boards. The control unit and the remotely controlled switch

Green that aluminum into something useful right in your own backyard by WB2CQM

Benefits in implementing a remote antenna switching system and a sample remote antenna switch project

The AE6AC 17-meter Moxon antenna project details the construction of a wire beam using readily available materials. This design utilizes four 16-foot fiberglass crappie poles for support, joined at the center with 3/4-inch Schedule 40 PVC pipe and "T" slip fittings. Wire segment lengths for 18.135 MHz were calculated using _Moxgen_ software by AC6LA, with specific dimensions provided in feet and inches for precise cutting. Key construction decisions include joining the crappie pole bases into a central hub and attaching the 16-gauge silver-plated copper wire to the pole ends. Dacron cord with a fisherman's knot secures the wire to the pole tips, while small wire loops at the corners maintain antenna shape. Plexiglas pieces serve as insulators for sections "A" and "C." The finished antenna, weighing less than 10 pounds, mounts on a fiberglass windsurfer mast and incorporates a 1:1 current mode ferrite bead balun. Performance measurements with an _MFJ-259B_ show an SWR better than 1.5:1 across the 17m band, with good front-to-back ratio and reported signal strength improvements of 2-4 S-units over vertical dipoles. Initial contacts included VK2AXB, ZF6GS, and KL1M.

An Unorthodox Antenna, originally by W3AWH is considered a multi-band antenna suitable for fixed location use and as an easily deployable portable antenna for events such as Field Days.

Delta 160-meter receiving antenna used at FO0AAA