Friday, December 23, 2016

Simple Ham Radio Antennas--Vertical Dipole in Tree


If you're having trouble viewing this video, please enter this title URL into your browser search box: https://www.youtube.com/watch?v=RI2_T-LeYEU. This is post #990 in a continuing series of Simple Ham Radio Antennas.  Here's another dipole antenna for those lacking the space to install a full-length horizontal HF dipole.  This antenna is vertical dipole fed with 450 ohm ladder line and arranged so that each element is suspended from a tall support such as a tree or telescoping fiberglass mast.  Stan Gibilisco (W1GV) does a good job of explaining the theory, construction, and use of this dipole variant. If the dipole is cut for the lowest frequency of operation and fed with ladder line, television twin lead, or  homemade balanced feeders, you will have a cheap, easily made dipole capable of covering several HF amateur radio bands.  An antenna transmatch (i.e. "tuner") with a 4:1 current balun is needed to match the feed line impedance to the impedance of your rig.  At my vacation home in the Puna District of Hawaii Island, I have a similar antenna covering the 20 to 10 meter amateur radio bands. The top end of the dipole is attached to a tree limb about 35 feet/10.67 meters above ground level.  Each element is a quarter wave piece of #18 AWG speaker wire connected to a center insulator and fed with 50 feet/15.24 meters of 450 ohm ladder line.  Each antenna element measures 16.6 feet/5.06 meters, which, with my "tuner"/balun combination, covers all amateur radio bands from 20 t0 10 meters.  As in Stan's example, all of my materials were obtained locally at no cost, thanks to garage sales and some supplies I had in the shack.  This antenna works very well and can be used as a portable or emergency HF antenna.
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Aloha es 73 de Russ (KH6JRM).