I was hoping to make a 220 version but I dont see why it wont work for every band just have to increase the number of cavitys to get the isolation up there. the copper jacket needs to change lengths though.
Off the top of my head: 6M = 68" 2M = 22" 220 = 15" 440 = 8" 900 = 5" 1.2 = not practical but most likely 3" For number of cavitys, I'd say 6 for 440 and 220, 6 to 8 for 2M and 8 to 10 for 6M. The dimensions I am using are basicly the same as a piece of Andrew 1 1/4 heliax (LDF6-50). Because 1 1/4 pipe was the thickest I could find localy, and 1/2" rod should be easy to come by. Another thing, In a duplexer only the rod that moves the plunger is invar, and the plunger its self is still copper. So maybe copper doesnt drift that bad on its own? I am considering using 1/2" brass all thread if I cant get invar, but I dont know how bad it shifts from tempretures, hopefully better than copper. What is scary is that when using all theread one cavity that is 22" long will contiunously tune from lower 2M to upper 440, but the rod would be hanging out so it would be unpractical. For the loop, just cut a 1/4" piece of pipe and flatten it. as plate copper is almost imposible to find anymore. The ends for the pipe are like $6 bucks, which kind sucks, but the top one will have a hole cut dead center and a 1/2" grade 8 nut inserted. This nut should be "Milled" round at the bottom so that it can fit into the hole (most likely 9/16") and silver soldered to the top cap. Once the rod is in the assembly, a Grade 8 jam nut will keep the rod it place. And another nut will be soldered to the top of the rod so the tunning tools can grip it, or a slot can be cut for a straight screwdriver, but I think using a wrecnh would be more precise. Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
