Okay. Since I got seven requests for the plans in a 20 minute timeframe (all already responded to), I'll take it there is some current net.interest and hereby notify r.r.a.m that I am about to post three articles covering the plans I mentioned before. To keep the plans "clean" of other garbage (so they are easier to save and print (one side one page, by design), I'll make my remarks here: 1. I hope someone enjoys building and using these antennas. The plans are not theory: I've built and used all these. 2. If you reprint these, please do not edit them down to a smaller size: I believe I've limited myself to a common information that cannot be substantially reduced. 3. Please do not remove my name from the articles: if there are problems/complaints I want to hear about them. 4. NOTE: I DO NOT claim to have invented/designed these! I have researched these designs at length and reduced the crutial construction information to a easily digested article. 5. There are other ways to build each of these. I only claim to have, by dint of research and experimentation to have hit upon a doable method. Experience with members of the Williamson County ARC (where I was in TX before I came to Atlanta and HP) proves that each of these antennas can be easily built and effectively used. If there are any gottchas, it is that the tv twin-lead j-pole must be carefully trimmed to tune; otherwise it is so-so. Cheers & 73 Ed Humphries N5RCK Hewlett-Packard NARC Atlanta GA edh@hpuerca.atl.hp.com The Copper Tube J-pole by Ed Humphries - N5RCK 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! 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. Other center freq dimensions: (adjust 5/8 section accordingly). 144 =19.25 inches, 145 =19.12, 146 =19, 147 =18.86, 148 =18.73. * Origin: Ham Echo Moderator / HDN Coordinator (214) 226-1181 (1:124/7009)