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The 5-in-1 J-Pole Antenna Solution for Multiband Communications

Experience versatile communication with this 5-in-1 J-Pole Antenna – your go-to solution for multiband excellence.

J-Pole: A Brief History

The J-pole antenna, more formally known as the J antenna, serves as a vertical omnidirectional transmitting antenna designed for use in the shortwave frequency bands. This ingenious antenna system traces its roots back to 1909 when it was first conceived by Hans Beggerow for deployment in Zeppelin airships. In this initial configuration, the J antenna was suspended behind the airship and comprised a single wire radiator that was half a wavelength long, in series with a quarter-wave parallel transmission line tuning stub. This arrangement was crucial for matching the antenna’s impedance to the feedline.

As technology evolved, so did the J antenna’s applications. By 1936, it had found its way to land-based transmitters, with both the radiating element and the matching section mounted vertically. This new arrangement gave the antenna its characteristic “J” shape, and it was formally christened the “J antenna” by 1943. The J antenna’s versatility and omnidirectional characteristics have made it a staple in the world of radio communication and broadcasting.

Multiband J-Pole Antenna Design

In scenarios where a multiband antenna is required, the deployment of individual J-pole antennas for each band can lead to installation complexities. The design presented in the figure below offers an elegant solution – a vertical element consisting of 5 J-poles, enabling operation across 5 different bands using a single pole.

Multiband J-Pole Antenna - Current Distribution and Radiation Patterns at Increasing Frequencies.
A sequence of 5 images illustrating the changing current distribution and radiation patterns of the Multiband J-Pole Antenna as the frequency increases from 27 MHz to 435 MHz.

In this configuration, each “J” corresponds to a specific band, and the position of the feed point is adjusted according to the operating frequency. The corresponding resonance frequency is conveniently indicated in proximity to the feed point for each “J”: 27 MHz, 52.5 MHz, 139 MHz, 224 MHz, and 435 MHz. It’s worth noting that the resonance frequency can be fine-tuned by modifying the feed point’s position. As a result, this design enables self-resonance, eliminating the need for a matching network and yielding a compact, robust solution that spans a considerable range of VHF and UHF frequencies.

The overall height of the pole in this configuration is approximately 5 meters, making it a practical choice for diverse radio communication and broadcasting applications.

Analyzing Current Distribution and Radiation Patterns

The figure provides a comprehensive view of the antenna’s behavior across its operational frequencies. Here, the current distribution on the antenna is depicted, allowing us to identify the active section of the antenna responsible for radiation at each frequency.

At the lower section of the figure, the radiation patterns are presented. Notably, these patterns showcase the antenna’s ability to maintain an omnidirectional radiation pattern in the horizontal plane, ensuring coverage in all directions. However, as the operating frequency increases, the pattern gradually distorts, as clearly demonstrated.

For in-depth analysis and simulations of this antenna’s performance, we offer the AN-SOF model, which includes pre-calculated data. You can easily access this model by clicking the provided button below the figure. It’s important to note that this model intentionally excludes a ground plane, allowing us to isolate and examine the antenna’s behavior without external factors that may influence its performance.

This 5-in-1 J-Pole Antenna solution empowers engineers and radio enthusiasts with a versatile tool for achieving multiband excellence. If you have a keen interest in J antennas, we invite you to explore our article, where we model a J-fed collinear antenna designed for the 2 m band.

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