From philabs!prls!mips!sdd.hp.com!hplabs!hpfcso!hpfcdj!keith Wed Oct 24 09:48:59 EDT 1990 Article 26876 of rec.ham-radio: Path: philabs!prls!mips!sdd.hp.com!hplabs!hpfcso!hpfcdj!keith >From: keith@hpfcdj.HP.COM (John Keith) Newsgroups: rec.ham-radio Subject: Re: J pole antenna plans for 2M Message-ID: <18230044@hpfcdj.HP.COM> Date: 21 Oct 90 14:30:13 GMT References: <110392@philabs.Philips.Com> Organization: Hewlett Packard -- Fort Collins, CO Lines: 54 Here's a variation on the twinlead J-pole design that uses copper tubing. The dimensions are a little different and the feed is different from what has been previously posted but then that offers some opportunity for experimentation (which is part of what amateur radio is all about). I haven't personnally constructed one of these but I know several local hams who have and they are very pleased with the results. This makes a very unobtrusive and rugged antenna. John Keith KD0GD SIMPLE J POLE ANTENNA The J-pole antenna offers good gain, compact size, simplicity and very low cost. They are easy to build and compare very favorably against commercially available antennas. As a side benefit they are DC grounded for lightning protection. The construction style provides for a very durble antenna and one that is very easy to mount. The total material costs should be about $10. Material list: 1) One ten foot piece of 1/2" rigid copper tubing 2) One 90 degree elbow fitting 3) One T fitting 4) Two 5/8" rubber chair leg caps (or 2 copper end caps) 5) Two small stainless steel hose clamps Construction: | | 1) Cut the copper pipe to the following lengths | (save the piece that is left over): | 57" (66 1/2" for a 5/8 wave) | 57" 19" | (66 1/2 3/4" (used to join the two fittings) | for 5/8 2) Using normal plumbing techniques (solder, | wave) flux, torch) connect the tubing as shown | | in the illustration. | | 3) Install either the rubber feet or solder 19" | | the copper end caps in place. | | 90 elbow-> |---| <- T Tuning: | fitting | 1) Attach the hose clamps about 3" up from the | <- left bottom of the "U" (5" for the 5/8 wave). | over 2) Attach the inner conductor of the coax to the 19" side and the braid to the 57" (66 1/2") side. 3) Check the SWR. Slide the clamps with the coax up or down until a 1:1 SWR is achieved If the copper color is not to your liking, paint it any color you wish. It is strongly suggested that you use a good silicon compound to weatherproof the coax connections against the elements.