From frbspd@crl.crl.com Sat Dec 4 11:04:52 1993 Date: Sun, 28 Nov 1993 01:40:44 -0800 From: Stephen Dunifer To: frbspd@crl.com Newsgroups: rec.radio.amateur.antenna Subject: (fwd) Re: Copper j-pole antenna - where? Newsgroups: rec.radio.amateur.antenna Path: nntp.crl.com!decwrl!ames!haven.umd.edu!news.umbc.edu!europa.eng.gtefsd.com!uunet!newsflash.concordia.ca!hobbit.ireq.hydro.qc.ca!barde!vaillan From: vaillan@ireq.hydro.qc.ca (Clement Vaillancourt) Subject: Re: Copper j-pole antenna - where? Message-ID: Sender: news@ireq.hydro.qc.ca (Netnews Admin) Reply-To: vaillan@ireq.hydro.qc.ca Organization: Hydro-Quebec (IREQ) References: <2cpn5e$gfr@desiree.teleport.com> Date: Mon, 22 Nov 1993 13:45:57 GMT Lines: 95 In article gfr@desiree.teleport.com, genew@teleport.com (Gene Wolford) writes: >Dick Partos (partos@larry.larc.nasa.gov) wrote: > >: > Anyone out there know what issue of 73 had the constructionarticle on a >: > copper j-pole antenna? Thanks. >: >K > >: I'm pretty sure it was the April 1993 issue. I've been meaning to copy >: it myself. > >Also see April 92 CQ "Electricians Delight" antenna. > >73's >Gene >KB7WIP And if you don't have copies, try this one, you can cut it, solder it and tune it in 30 minutes! 73 Clem. --- Clement Vaillancourt, | Institut de Recherche d'Hydro-Quebec Analyste, | Varennes, P. Quebec, Canada, J3X 1S1 Informatique scientifique | Tel:+1 514 652 8238 Fax:+1 514 652 8309 vaillan@ireq.hydro.qc.ca | Radio-amateur: VE2HQJ@VE2CRL.PQ.CAN.NA > From: Ed Humphries > Subject: Re: Copper Jpole! > To: Vaillan@ireq.hydro.qc.ca (Clement Vaillancourt) > Date: Wed, 17 Mar 93 15:04:50 EST > > The following is a description of a J-Pole antenna made from copper > pipe. You can use 1/2 inch to 1 inch pipe (wall thickness will > affect stiffness/stability AND price, but not performance). Larger > diameter pipe increases bandwidth, but 1/2 inch is fine for amateur > frequencies. Start with a 10 foot (standard) length of pipe, 1 90 > degree (right angle) fitting, 1 "tee" fitting, 2 end-caps, 2 hose > clamps (worm-gear adjustable of the appropriate diameter), and your > coax (end stripped, braid separated, center conducter stripped, and > coax sealant to close opening in coax to keep water out). Use a tube > cutter (for best/easiest results) and cut the 10 foot pipe according > to the dimensions needed following the diagram below: > __ > | <=endcap > | > | > 5/8 | > or | > 1/2 | > wave | > | > | > | > -- | | <=endcap > | | 1/4 > | | wave > | | > coax ctr conductor=>* *<= coax shield > | | > @ 5"-->| | > tee => --- <= elbow > | > | < "leftover" pipe > | > > For best general purpose use, the 5/8th wave version should be > used. The dimensions to cut are: 66 1/2 inches (5/8 + 1/4 matching > section), 19 inches (other half of 1/4 matching section), 3/4 inch > (joins the tee and the elbow), and the "leftover" 33 3/4 inchs that > forms the base. Use standard plumbing solder methods to join main > section to base using the tee. Use the 3/4 inch piece and the elbow > to attach the 19 inch piece. Be careful to keep pieces parallel. > > This will give you a center frequency of 146 MHz. Attach the coax > as shown using the hose clamps. Adjust the swr at 146 MHz by sliding > the connections up or down as needed -- you should be able to reach > very close to 1:1 (best to do this in approximately where you intend > to use the antenna - the base can be attached directly to a mast by > two hose clamps). Try not to be standing right by the antenna! > > Purists will note this is an unbalanced antenna and that a 1-to-1 > balun is called for - practically this proves to be unnecessary. It > has been noted that this design can lead to rf coupling onto the > feedline. To avoid this, put a ferrite on the coax at the feedpoint, > or use 3 turns (@1") of the coax taped together at the feedpoint. > Some people reverse the coax shield and center conductor. > > Other center freq dimensions: (adjust 5/8 section accordingly). > 144 =19.25 inches, 145 =19.12, 146 =19, 147 =18.86, 148 =18.73.