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jpole2.txt
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1994-08-24
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From frbspd@crl.crl.com Sat Dec 4 11:04:52 1993
Date: Sun, 28 Nov 1993 01:40:44 -0800
From: Stephen Dunifer <frbspd@crl.crl.com>
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: <CGwBKL.1I6@ireq.hydro.qc.ca>
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 <edh@hpuerca.atl.hp.com>
> 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.