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>I'm replacing my 6 ft. quadpod roof tower with a somewhat >unconventional 10 footer (an older, refurbished TET model that >has a 4 foot base as a quadpod and a 6 foot, 4 sided, 6" face top >section >that will need to be guyed). > >The tower is kinda funky looking, hard to describe. >The vertical section is just that...thrust bearing on top, rotor >shelf to the second-to-the-bottom shelf. Total height is 6'5". <snip> There are probably at least four suppliers of similar aluminum erector set towers in JA, as well as a number of copy products from HL vendors. There are literally tens of thousands of these things in use, only not so many in NA, I would imagine. <snip> >My plan is to put the C3-SS up 4 or so feet over the thrust bearing. >I have a F12 rotatable dipole (actually, a C3->C4 expansion >kit), and want to put that above the C3-SS. If the TET is anything like my 5.7m Maldol (or was it a Comet, it's been so long since I bought it I've forgotten), you'll be okay as that load is far less than what we put on them here. >The questions are: >-what's the recommended material for guying? I'm still using the same kevlar halyard ten years & three QTHs later. Something like 4mm diameter I think it was. Same used for some half dozen other installations here, all of which were still standing after typhoons, although not all the antennas on top of them survived. None of which were F-12 products, obviously! >-how high do I put the rotatable dipole over the tribander? As high as possible? The worst thing for these towers, in my experience, is torque from long booms, or ones with a bit of windage (a KT34 on mine required tag lines on the boom at times, even not during typhoons, before I could sleep at night). Although a blatant no-no, I used to hoist a 1.8 Mc inverted-vee from the top of the 5m of mast I have extending from the top of mine. The 5m of mast is still there today for top loading (I shunt feed the tower for 3.5 Mc). When the KT34 was on the tower, I had a 6m yagi with some 4m of boom as far up the mast I could reach yet still tighten the boom-to-mast bracket - nearly 3m. The C4 7 Mc element of yours shouldn't be too much of a worry. >-does the rotatable dipole go perpendicular or parallel to > the tribander elements? I would be tempted to try parallel as I would be wanting to use it in the same direction as the tribander & in its originally intended application, it's parallel. I have yet to get my own C-4E/A on to the tower, so to be honest, Natan or others with experience in flying F-12 products will no doubt chip in with a suggestion. >-does the rotatable dipole need a balun? It's a balanced antenna fed with an unbalanced feeder, which tells me something should be done. With nothing but roof-top antennas in apartment QTHs for the last two cycles, I regret not learning that some kinda choke on the feeder of unbalanced lines going to even unbalanced antennas is worthwhile, as they keep RF out of the shack & crud from the shack (like from a computer) from getting into the antenna & covering up weak signals one wishes to hear. Enjoy! 73, VR2BrettGraham -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force12 Web Site: http://www.force12inc.com To Submit Message to the List: Force12Talk@qth.com To unsubscribe and view the Message Archive: see http://qth.com/force12/list For problems with the list: contact n4zr@qth.com |
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