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Dear Friends, Good afternoon to the Force 12 Reflector regarding the gain specifications of the Tennadyne T-10, our RK-10L and the C-31XR, plus a comment about the 5BA. First the 5BA having a "fatal flaw" regarding mechanical issues - I was just at the Visalia DX Convention last weekend and a fellow came to me right away Thursday evening (the day before the convention began, as I get there early in order to set up demos, etc.). He introduced himself and told me that in a terrible storm last winter, all of his non-Force 12 antennas came down except his 5BA. The storm set the new 100 year records. There certainly are exceptions in weather conditions and one who lives in those zones should make it known at the time of order, regardless of the company they purchase from. I have tracked wind patterns and storm types for several years and know how to build antennas to meet any conditions. We build several now for 140 mph and one just shipped was a C-3S/HH. For reference, a stock C-3S for 80 mph (survives usually >100) weighs 26 pounds. The /HH for 140mph weighs 72 pounds. We offer various wind ratings for our products and make compensation for abnormal conditions such as uplifting winds or extraordinary velocity. On to the gain issue: W4RNL's figures are correct and track modeling using NEC IV. The Force 12 LPDA gain specs are within a reasonable region. A classic LPDA design (i.e. 7 elements per octave and matching boom length) will most likely not exceed 3dBd, such as the Force 12 RK-7L. The RK-10L is a compressed boom length (in the 10-14 MHz range) design for installation reasons (built to a commercial spec) that covers 10-30 MHz, so the gain range is 2.1-3dBd. The lower gain region is at the lower end of the frequency coverage range. Populating the boom with more elements for the same design range improves the gain, as more elements come into play at any given frequency; however, it will rarely, if ever match a 2 element Yagi for the desired band(s). If the LPDA boom is extended and heavily populated, it can do more, even reaching a 3 element Yagi design. Believe LB Cebik's figures; otherwise, prove them wrong! We can't wait for Ward and Steve to do another test of HF arrays, hopefully including our XR-5 versus a commercial log. An XR-5 overlaid multi-monobander has resonate elements for 20 through 10 including WARC on a single 18' boom and we strongly suspect the 2 el. resonate overlay will provide more gain than a comparably boomed log. Let the testing begin! Someone called into question our calculation of the C-31XR gain as being possibly "totally outrageous", like the Tennadyne T-10 gain figure. Not hardly. We not only do our own in-house modeling, but we also utilize outside consultants to be sure the figures are right. If the learned consultant comes up with lower gain, we use that number. So far, our numbers have been right on. The reason an outside independent consultant is used is 2-fold: a) because one of the reasons for the company being founded was to provide real gain data, not the fluff that had been given out for way too long; b) I give talks and seminars all year long and if the figures weren't right, I would look pretty foolish trying to defend them. The C-31XR has been run by many people known and unknown and the figures are correct. Anyone familiar with Yagis will know at a quick glance that the C-31XR figures are absolutely reasonable. Our LPDA figures are also right and both LPDAs have been compared real time to 2 ele and 3 ele Yagis over several months. LPDAs have their place when broad frequency coverage with low VSWR (i.e. <2:1) is the primary concern. When we are using bands, which are very narrow in terms of typical LPDA coverage, LPDAs are easily surpassed by shorter boom non-trapped multi-monobanders. The two gain figures in Force 12 literature are included to address two issues: a) the Net Gain figure is the one I prefer, as it gives the apples-to-apples figure for horizontal antennas (not verticals); b) the gain at 74' is included because of many requests for a figure to relate to typical modeling data with the horizontal antenna above real ground. Nothing more than that. This figure can be even calculated, so its nothing too spectacular. Just a thought here - has anyone received Tennadyne's model? Any LPDA model (much less the real thing) that can exceed the gain described in work by W4RNL should be elevated to high prominence. 73 and maybe we can get some incredible propagation to ZA so the west coast can get them on 80! Tom, N6BT -------------------------------------------- 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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