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![]() "Desmoface" ... anyone think a verticle dipole would work. ..a vertical dipole for 10... Steve kb8viv How about a J-Pole? ..one using a mast with the 1/4 wave parallel section added 1/2 wave below the top. Real easy. No radials. John Smith - KD5YI As others have already noted, vertical dipoles do work whether center-fed or end-fed (a.k.a. J-pole) without radials. As already noted, hang it as high as you can manage - just the normal advice for any antenna except N.V.I.S. If you want to pursue the J-pole route, go to CQ magazine's web site http://www.cq-amateur-radio.com/ and download George VE3ERP Murphy's freeware HAMCALC ham radio software package. (lower left corner) (Download it just for general principles.) Program about-23 of 250+ programs is Murph's version of my version of Gary N3GO O'Neill's J-pole program from his Communication Quarterly article on end-fed half-wave antennas. Go to Steve AA5TB Yate's website http://www.qsl.net/aa5tb/ under "Antennas" for more info and a link to Gary's article on how J-poles and Zepps really work versus the popular view. The program gives starting lengths. For 28.5 MHz: Using 300 ohm twinlead: halfwave radiator wire = 196.7 inches series matching 300 ohm section = 78.6 inches to the 50 ohm tap point shorted shunt stub 300 ohm section = 6.6 inches Total length is about 23.5 feet if you hang it all up vertically. The not-quite-quarter-wave matching section can be horizontal with the halfwave radiator vertical if you need/want to run it that way. Gary's article, the program or a Smith chart show why the commonly used 450 ohm ladder line is not the as good a choice for matching as 300 ohm. Have fun. Measure and cut metal and plastic, hang it up, apply and withdraw RF energy. Don't just do computer calculations (as I do most of the time (sigh)). Cheers, 73, Ron McConnell N 40º 46' 57.9" W 74º 41' 21.9" FN20ps77GU46 [FN20ps77GV75] http://home.earthlink.net/~rcmcc |
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