. QST . struction The antenna is made from two pieces of H-inchdiameter electrical thin-wall steel tubing or con-duit. This tubing is readily available at any elec-tric supply shop and sells for approximatelyseven cents a foot. It comes in 10-foot lengthsand, while 20 feet is short for a half-wave antennaon 21 Mc, with loading the length is just aboutright for 52-ohm feed line.^ If aluminum tubingis available, it can be used in place of the conduit,and the antenna will be lighter in weight. How-ever, it is sometimes difficult to obtain aluminum,while steel thin-wall conduit is available in any
. QST . struction The antenna is made from two pieces of H-inchdiameter electrical thin-wall steel tubing or con-duit. This tubing is readily available at any elec-tric supply shop and sells for approximatelyseven cents a foot. It comes in 10-foot lengthsand, while 20 feet is short for a half-wave antennaon 21 Mc, with loading the length is just aboutright for 52-ohm feed line.^ If aluminum tubingis available, it can be used in place of the conduit,and the antenna will be lighter in weight. How-ever, it is sometimes difficult to obtain aluminum,while steel thin-wall conduit is available in anyelectrical supply house. As can be seen in Fig. 1 and the photographs,the two pieces of tubing are supported by fourstand-off insulators on a four foot long 2 by coax fitting for the feed line was mounted onthe end of one of the lengths of tubing. A mount-ing point was made by flattening the end of thetubing for a length of about 114 inches. The tub-ing can be flattened by squeezing it in a vise or. This view shows a close-upof the coil and coax fittingmountings. Be sure that thecoil doesnt short out to theouter conductor when solder-ing the coil end to the innerconductor pin on the coaxfitting. 30 QST for Fig. 1 — (A) Diagram of theantenna and mounting. TheU bolts that hold the 2 by 2to the floor flange are standard2-inch TV mast type bolts. (B)A more detailed drawing ofthe coil and coax-fitting mount-ings. The J^-inch spacing be-tween turns is not critical, andthey can vary as much asMe inch without any apparentharm to the match. I Floor Flanae tPipe —1- r X 2*2-4 Lon^ (A)
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectradio, bookyear1915
