Vk2abq Beam 20m,15m,10m

The VK2ABQ Beam Antenna for 20m,15m & 10m as built by ZS1JHG

This is an easy to construct tri-band beam antenna that will give similar performance to other commercial wire two element beams. I would recommend using black plastic coated stranded wire of about 1.6mm in place of the solid copper enamelled wire. This will prolong the life of the antenna in windy conditions. Remember to rig the antenna first with full full wave loops. Check with a GDO and trim the loops to your selected resonant frequency, then cut and insert the button insulators to form the reflector and driven element sections. To improve the construction I would attach an arm to support the feedline (suggest PVC conduit 25mm). The arms (spreaders)at each end can also be guyed to a central mast attached to the centre hub. This will limit sagging. If you cannot locate 75 ohm twinlead then use UV resistant black twinflex (the GPO type I tested was about 85 ohms).

Page 2 Bamboo arms or spreaders are not recommended due to weight and water absorption. If you must use them tape well with the wide PVC black insulation tape .Varnish is not recommended as it soon peals off due to flexing. When rigging up the antenna attach the hub to a stub mast about 1.5m long and place in a sturdy drum or the Hams best friend after the YL a bench vice (“Workmate”). This will allow you to rotate the antenna as you rig it up. Tuning the antenna as mentioned before is with the aid of a GDO Place a two or three turn loop across the feeder at the mounting board hub (Marked X on the diagram) and dip for the resonant frequency, Trim the wire for the low end of the band as when the antenna is placed on your mast or tower this will put you mid band. Tuning needs to be accurately done for best performance as this is a fairly high Q antenna Design.

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