Submited By Nadisha 4S7NR
The X-Beam is a high-performance broad-band antenna that is ideal for Ham radio operators with limited space. X-Beams are inexpensive and easy to build. The X-beams described here were designed and built by Brice Anderson W9PNE. This material first appeared in the ARRL Antenna Compendium Vol-1. For the QRP Circuits site, I (Nadisha 4S7NR) copied this article from ARRL Hand Book 1996. Please find the original article on any of the above mentioned books for more details.
Diamentions for X-Beam
|Formulas Formulas||Full size X-Beams||Minimum Size X-Beam
|Arm Length (ft)||= 195/f (MHz)||= 177/f (MHz)
|Each Driven Element Tail Length (ft)||= 106.5/f (MHz)||= 125/f (MHz)|
|Each Director Element Tail Length (ft)||= 92.5/f (MHz)||= 110/f (MHz)|
The minimum size version of X-Beams, may be not the ideal one for QRP work. But if you wish to have a 30m or 40m beam, that is not a bad idea at all. The diameter of Aluminium tube used for Arms are 200:1 length to diameter ratio. Do not use arms longer than calculated by the full-size formula. As the Arms get longer and the tails get shorter the pattern changes gradually to four broad lobes. Tails should be horizontal to the wooden plate and not be hanging. To keep them horizontal, you will have to use a nylon string tied around the beam from arm tip to tip.
Tails should be made few inches longer than the calculated lengths for the tuning prepossess. For tuning Beam should be mounted on a pole at least 10 feet from the ground. When you trim the antenna tails for tuning, try to keep the driven to director tail ratio as much as possible for best pattern. If you wish you could add a simple balun (coil the co-ax feeder for 6 inch internal diameter ring with, 12 turns for 15 and 20 meter, 6 turns for 10 meters.) for better performance.
The performance of the simple X-beam is amazingly similar to larger, more conventional antennas. Put one up and challenge the big guns.
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