This article was originally published in 2020 as part of the HamZone community's trial run and has been reprinted from. @BH2RSJ
- This antenna is called the JCU antenna. This type of antenna was occasionally seen in the book "(Near-Orbit Satellite Communication Shortcut)", and the author's intention was to create a compact, directional antenna that avoids the complexity and weight of multi-unit octagonal designs. If this antenna is constructed according to the author's diagram, it can be directly attached to the handrail for communication. The gain is very good.
- The antenna structure is shown in the figure. The front end consists of a circular array, and the back end has a reflector. Many hams initially recognize it as a Moxon antenna with an added reflector, but this is not entirely accurate. A Moxon antenna consists of two units arranged in an eight-element, inward-folding configuration, with an open array structure. The key difference here is that this circular array is closed, unlike the Moxon antenna which is designed to suppress interference from the rear while providing good gain in the forward direction.
- The antenna's performance is good; after being manufactured according to the diagram, it requires very little adjustment and can be used normally for UHF amateur radio operation at 430-440 MHz with a gain of 9.6-12 dBi. The actual communication effect is excellent. The antenna has a forward polarity; to ensure that the polarization direction matches that of the amateur radio station, it needs to be used horizontally, as shown in Figure 5.
- Construction: The antenna construction is relatively simple. For example, you can use PVC pipe with a diameter of 25mm. The elements can be made of 2mm stainless steel or copper wire. The spacing between the feed points and the size of the main frame affect the standing wave ratio (SWR). Adjust the SWR to around 1.2. The diameter of the antenna array has little impact on the antenna itself. In my diagram, the quick-connect version is a "hexagonal connector" that can be found on Taobao by searching for "quick-connect".
- Due to the electrical dimensions of the antenna being determined by the frequency used, do not significantly alter the antenna size without proper design. This can lead to uncontrollable standing waves and magnification based on wavelength. VHF antennas are very large, so it is not recommended to build one.
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