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writes: > k8dxx@home.com> > To: <Force12Talk@qth.com> > Subject: [Force 12 Talk] Tuning on 40 meter linear loaded elements? > Date: Thu, 12 Apr 2001 23:06:01 -0400 > > I am about to put up a C4XL. > > I just got off the air with a couple guys who reported some difficulty > getting Force 12 linear loaded 40 meter elements to tune easily. One OM had > the EF140S added to a C3SS. The other had the EF240S as a separate antenna > (although it was mounted above, not below a C3...problem?). Both reported > tuning jumper settings being much further from the spreader than > recommended in the manual. One guy reported having to add another turn to > the hairpin match. The GOOD NEWS is that both reported performance being > worth the effort! > > My question to EF140S derived antenna owners is what jumper setting did you > find successful and at what tower height? I've put up over a dozen F12 linear loaded antennas and the dimensions in the manual are just a STARTING PLACE. I've NEVER seen one that didn't need re-tuning from the original measurements. > How about the hairpin match; any modifications aside from squeezing or stretching? The coil just fine-tunes the swr and doesn't have anything to do with DE resonance. Once the antenna resonates where you want it, then you open the coil until you get the lowest swr. > Also, I will probably > have an antenna analyzer available to me. If you have used one to tune up > an EF140S, did you use it at the end of a long coax run or using a short > piece of cable. For all F12 linear loaded antennas, you need to resonate each element. In this case of a 40M dipole that's easily reached from the tower, it's a piece of cake. When the antenna is installed, you put your antenna analyzer on the feedpoint with the coil and tune it. When you've got it where you want, put the balun and feedline on and check it at the shack. Since you're only really interested in what it looks like at the shack, you may have to do some minor changes if it looks different at the end of the coax. For multiple element beams, you can't reach the other elements from the tower so you either need a crane or you can run it up and down on the installation tramline. You just need it 20-25 feet off the ground to see where it's working. Take the jumper off of the parasitic elements and tune them like a dipole; I've got a PL-259 with alligator clips that I use for feedpoint attachment and a 25 foot long piece of RG8 I use for antenna tuning. The resonate frequencies for all elements are given in the F12 manuals so go ahead and tune them for the appropriate frequencies, put the jumper back on when you're done and you'll be in business. Cheers, Steve K7LXC Tower Tech <A HREF="http://www.championradio.com">Champion Radio Products</A> -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force 12 Web site: http://www.qth.com/force12 Submissions: send to Force12Talk@qth.com To unsubscribe: send a blank e-mail to Force12Talk-leave@qth.com Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk For problems with the list, contact n4zr@qth.com |
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