From netcomsv!decwrl!doc.ic.ac.uk!uknet!pipex!howland.reston.ans.net!darwin.sura.net!haven.umd.edu!ames!dale.ksc.nasa.gov!titan.ksc.nasa.gov!k4dii.ksc.nasa.gov!user Tue Sep 28 18:22:58 PDT 1993 Article: 945 of rec.radio.amateur.antenna Path: netcom.com!netcomsv!decwrl!doc.ic.ac.uk!uknet!pipex!howland.reston.ans.net!darwin.sura.net!haven.umd.edu!ames!dale.ksc.nasa.gov!titan.ksc.nasa.gov!k4dii.ksc.nasa.gov!user Newsgroups: rec.radio.amateur.antenna Subject: Re: Wire J-pole? Message-ID: From: fred-mckenzie@ksc.nasa.gov (Fred McKenzie) Date: 27 Sep 93 15:29:31 EST Followup-To: rec.radio.amateur.antenna References: <1993Sep23.145919.9022@news.uiowa.edu> <286sqa$99m@geraldo.cc.utexas.edu> Distribution: world Organization: NASA, Kennedy Space Center, Florida Nntp-Posting-Host: k4dii.ksc.nasa.gov Lines: 48 In article <286sqa$99m@geraldo.cc.utexas.edu>, Barry Newberger, W5KH wrote: > I am aware of two articles. The first, by John Belrose VE2CV appeared in > QST, April 1982, p. 43 and the second in Ham Radio for August 1983 in Orr's > column on page 40. > Incidentally, Belrose found that the dimensions were somewhat sensitive > to the velocity factor of the twin lead he used and his design specified Belden > 8230 ribbon. If anyone knows if this is still available and/or where one can > obtain this, I would like to hear from them. Barry- What a coincidence! Over the weekend, I came across a BASIC program derived from one of the Belrose articles. It was on one of those share-ware/public domain Ham Radio CD's, on a local BBS. Since it is short, I'll list it below. 73, Fred, K4DII ________________ 1 REM Data taken from article in April 1982 QST by John S. Belrose, VE2CV 2 REM Program written by Marv Hayes, NF6G, 3/20/83. 90 PRINT "These calculations are for a 'J' antenna made from 300 ohm" 91 PRINT "twin-lead such as Belden 8230 with a velocity factor of .8" 95 PRINT " " 100 INPUT "Please enter the design frequency in mHz";FREQ 105 PRINT " " 200 LAMBDA = 11811/FREQ 300 STUB = .83 * LAMBDA / 4 400 RADIATOR = .9650001 * LAMBDA / 2 500 TAP = LAMBDA * .0136 600 GAP = .25 1000 PRINT "DESIGN LENGTH OF LENGTH OF TAP GAP" 1100 PRINT " FREQ 1/4 WAVE RADIATOR DISTANCE DISTANCE" 1200 PRINT "(mHz) (inches) (inches) (inches) (inches)" 1300 PRINT " " 1400 PRINT FREQ, STUB, RADIATOR, TAP, GAP 1890 PRINT " " 1900 PRINT "If this antenna will be inclosed inside a PVC plastic tube," 1901 PRINT "the dimensions should be reduced (multiply by 0.95)." 1905 PRINT " " 1910 STUB = STUB * .95 1920 RADIATOR = RADIATOR * .95 1930 TAP = TAP * .95 1950 PRINT FREQ, STUB, RADIATOR, TAP, GAP 2000 END ________________________