Center post detail

In trouble shooting your hex beam it can be helpful to understand that the center post is nothing more than a piece of coax with terminals connected to it. There are no electronics inside the center post. It is just a tube with a bar running up the inside. The tube and bar are electrically a coaxial line. The bar is the inner conductor, the tube itself is the outer shield and the dielectric between them is air. The shape and spacing of the bar determines the characteristic impedance. In the case of the KIO hex beam center post, this characteristic impedance is about 50 ohms.

Since the hexbeam itself has a resonant impedance that luckily is close to 50 ohms, the center post is 50 ohms and your feedline is 50 ohms, the radio sees a good match and indicates a low SWR.

From the photo down into the center post with the cap removed, you can see there is little that can go wrong. The insulated wire terminals along the side are connected to the inner bar and the top of the bar is connected to the center pin of the SO239 connector. The other wire terminals are simply press in captive studs in the side of the tube. There is no electrical connection between the bar and the tube as you might expect since that would be a short circuit of the “coax” center post. On the other hand, all the insulated terminals are a solid D.C. connection to the inner pin of the coax connector at the top of the center post. There is a soldered joint of the bar to the inner pin of the coax connector. There is no stress on this joint and it is very unlikely that it will break loose. We test every center post electrically and make a very careful examination to be sure that every center post shipped is properly assembled and soldered.



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