OK, this has me intrigued. So the T top would look like this if looking straight up (or straight down) with the vertical portion at the xx?
x x x x x x x x x x x x x xx x x x x x x x x x x x x x My 160M dipole is actually a 160/80M fan and resonates well on both bands, I did not think I could do that with a T top. That would solve issues. Would a cage of vertical wires be better than if I could use 2.5 to 1.5" aluminum masting? Luckily in our rural local club we have 2 hams that sell some neat products, one is the Air-boss launcher and the other is the Antenna Tensioner. The tensioner has proven its self here in the eastern NC winds. And being a boating area I have several West Marine stores nearby. Gary Mitchelson NC3Z/4 Pamlico County, NC FM15 On 07-Mar-16 12:48, Jim Brown wrote: > Hi Gary, > > The antenna you describe should work quite well on both bands, but I'll > suggest a couple of tweaks to make the matching easier. First, make it a > Tee -- if you have a catenary, you can support a Tee as easily as an L. > Second, make the top section a fan (like a fan dipole) with short > elements to resonate it on 80 and longer ones for 160. Third, don't > worry about remoting the tuner unless you feedline is very long. Unless > the match is really bad, feedline loss on 80 and 160 is pretty low, > especially if you use RG8. Also, you can make the tuning more broadband > (and electrically lengthen the vertical section by 1-2 percent) by using > two parallel runs spaced 12-18 inches, tied together top and bottom. Do > a simple NEC model to get dimensions. > > Finally, use as many radials as you can, don't worry a lot about length, > just think more is better. :) BTW -- 50 ft on the ground will be close > to a quarter wave on 80, 100 ft on 160. > > As to physical details -- get a good pulley at each end, tie one end > down, put a weight on the other end, and use some sort of "mechanical > fuse" at the feedpoint so that wind doesn't break it. I use a mating > pair of Pomona connectors -- when the wind blows, they simply un-mate. > For the fan spreaders, cut short lengths (12-18 inches is great) of > 1/2-in PVC conduit, drill holes about 3/4-in from each end to pass the > wires through. Make this antenna as physically robust as possible to > withstand the wind. At a minimum, #10 THHN for the long top sections > that carry the stress. #12 or #14 is fine for the shorter top sections. > Don't make any soldered connections -- they don't weather well, and wire > tends to break at a soldered joint. Instead, use split-bolt copper clamp > connectors sized to fit the wire you're using. For support rope, use > 5/16-in rope from http://www.synthetictextilesinc.com/supportham.html > It's resold by lots of ham vendors, but Synthetic Textiles is a bit > cheaper. Smaller rope is sufficient for strength, but you'll appreciate > the larger size when you're trying to pull on it to maximize tension, > which pulls it higher. :) Don't use hardware store pulleys -- instead, > use marine pulleys (good) or this excellent "rescue" pulley, which is > also easy to rig. > > http://www.ropescoursewarehouse.com/catalog1/advancedwebpage.aspx?cg=1851&cd=4&SKUTYPE=202&SKUFLD=SKU&DM=1250&WEBID=914&gclid=CKfCobGOr8sCFQWUfgod5DUOHQ > > > Out here in CA, the West Marine is the place to buy marine pulleys. > > 73, Jim K9YC > > On Mon,3/7/2016 5:50 AM, NC3Z Gary wrote: >> Now I want to be able to use this antenna for 80M as well as the non-DX >> portion of 160M. I can house a autotuner at the base (or make my own >> network but that would require control lines). My thinking is to make >> the 160M a 5/16 WL vs 1/4 to be more beneficial to 80M tuning without >> loosing anything on 160M. > > _________________ > Topband Reflector Archives - http://www.contesting.com/_topband > . > _________________ Topband Reflector Archives - http://www.contesting.com/_topband
