Off-Center Fed Antenna: DIY Build Guide
Construct Multiband Performance Antennas
Off-Center Fed (OCF) antennas are a versatile choice for amateur radio operators seeking efficient multiband performance. These antennas are particularly beneficial for those with limited space, as they can effectively cover multiple HF bands, including 80m, 40m, 20m, and 10m. The OCF dipole is fed at a point that is not the center, allowing for a wider range of frequencies without the need for extensive tuning. This makes it an ideal project for both beginners and experienced builders looking to enhance their station's capabilities. Constructing an OCF antenna involves straightforward techniques that yield reliable results.
To build an OCF antenna, you will need high-quality wire, a 4:1 current balun, and insulators for the ends. The typical design consists of a length of wire cut to specific lengths for the desired bands, with the feed point located off-center. Additionally, coaxial cable is required to connect the antenna to your transceiver. Proper installation and positioning will maximize performance, ensuring effective communication across various frequencies. This project is not only rewarding but also enhances your understanding of antenna theory.
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This is a popular antenna design as the performance is very good across the HF bands and requires little or no tuning. It is a dipole fed off center with a 4:1 current balun at the offset feedpoint. The antenna shown covers 80, 40, 20 and 10 meters with 15 meters and WARC bands -
Multiband Center-Loaded Off-Center-Fed Dipole (CL-OCFD) antenna that work on 80m 40m 30m 20m 15m 10m. The Center-Loaded Off-Center-Fed Dipole (CL-OCFD) antenna, developed by Serge Stroobandt, offers a versatile solution for amateur radio enthusiasts, covering multiple HF bands (80, 40, 30, 20, 15, and 10 meters) without the need for an antenna tuner. This innovative design utilizes a capacitor for resonance on the 80-meter band and a resistor to manage static charges. The CL-OCFD enhances bandwidth and simplifies operation, making it a significant advancement on OCF Dipole design. -
Off-center-fed dipoles (OCFs) are 1/2-wavelength wire antennas fed at neither the center nor the end, but somewhere between--off-center -
Up, Up, and Away or Harmonic Operation of OCFs -
An Off-center-feed antenna that covers 80, 40, 20, 17, 15, 12, 10, and 6 meters -
A 144 MHz dipole antenna made from coax, PVC pipe, and aluminum foil tape -
This was an investigation into whether an inverted V dipole could be fed offcenter to work on 20, 17, 15, 12, AND 10. -
A slightly different 6M antenna project by N1GY, an Off center fed antenna for the 50 MHz. -
The behavior of a straight dipole and its L-form is examined in terms of impedance and SWR. By adjusting the feed point or bending angle, impedance variation is observed. Impedance shifts symmetrically as the feed point deviates, leading to recommendations for optimal ratios. Model simulations aid in understanding and fine-tuning, crucial for achieving a 50 Ohm match. Practical tuning guidelines ensure efficient antenna performance. -
This antenna is not a true Windom, but rather an off center fed or OCF dipole works on 8 bands from 80 to 10 meters -
An article describing a homemade 40m wire OCF Dipole -
A simple 7 bands off-center dipole wire antenna designed to work on 80 meters band and that can cover also 40m 30m 20m 15m 12m 10m with acceptable SWR -
This page is a discussion about impedance matching by Off Center Fed dipoles in the Wide L-form. When a vertical or horizontal dipole is bent into a 90 degree L-form, the impedance drops about half. -
This page provides information on how to design an Off-Center-Fed Dipole (OCFD) antenna, suitable for amateur HF bands like 80 meters or 40 meters. The antenna design allows for VSWR minima on multiple bands, making it a good choice for multi-band use. Learn how to create an OCFD antenna in either flat-top or inverted-Vee form using a single support. The page also offers tools to generate radiation patterns, VSWR charts, and antenna current diagrams for your specific antenna design, helping hams understand performance factors. Ideal for ham radio operators looking to build their own effective antennas. -
This article discusses suitable first HF antenna options for amateur radio operators with limited space. It recommends an Off-Center Fed (OCF) Dipole and a Vertical Dipole, detailing the installation processes, considerations for stealth and ease of setup, and the characteristics that make them ideal for newcomers. Safety warnings and maintenance tips are provided to ensure effective and secure operation. -
This type of antenna is a popular antenna design as the performance is very good across the HF bands and requires little or no tuning. It’s a dipole fed off center with a 4:1 balun at the offset feed point. The antenna shown covers 80, 40, 20 and 10 meters. The formula can also be used to adjust the overall length to cover more or fewer bands and the resulting overall length. 160-10m, 80-10m or 40-10 meters depending on your available space. Other bands will require a tuner. -
7 Band OCF Antenna project by W0HC -
About windom antennas and OCF dipoles, tricks on covering more bands moving feed-points and potential problems. Problems caused by common mode currents in OCF dipoles -
A page descibing the principles of OCF antennas also known as windom antennas by DJ0IP -
A multi-band off centre fed dipole, designed to operate on all bands from 40m (7MHz) to 6m (50MHz). Author claims it will operate on 40, 30, 20, 17, 15, 12 and 10m without an ATU (SWR <3:1) plus 6m with an ATU. -
The OCFD Off-Center-Fed Dipole Antenna is an excellent multiband antenna that is relatively simple to construct, yet gets quite decent performance.