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and/or the FORCE12Talk reflector - Regarding his comment, "Too bad Tom never reads this stuff." I obviously do read "this stuff". There are other avenues of communications besides his Tower Talk reflector. Anyone with a question or comment on the Force 12 product line has an 800 line, the FAX number has always been available, our E-mail support is still active, the US Mail is available, there is now the Force 12 Reflector and I am available at conventions and club meetings. I believe that going to the appropriate source is the most effective and proper route. After all, if you have a question or comment that you want to have answered about your Jeep Cherokee, do you go to a GMC reflector? Regarding the integrity of the standard 3KW B-1 baluns (same construction on the larger B-1/C, but the B-1/5KW is a toroid design in a sealed box): This has been addressed several times before on a reflector, as well as in person and even last week in an e-mail to a customer. A balun (regardless of who makes it) is not part of the boom structure; therefore, it is not necessary to apply excessive pressure during mounting so that the body of the balun is broken. I initially secure the balun using good quality tape around the coax and the boom, about 3 inches from the connector end of the balun, leaving a slight amount of slack in the balun leads. The balun can then be secured to the boom with minimal pressure using tape or tie-wraps (remember to cut the tie-wrap close, or trim the corners to avoid the possibility of cutting yourself). The core of the B-1 balun is solid epoxy around the Teflon coax and is placed in a vacuum chamber during construction. There are no voids. We have received a few back from antennas loaned to DXpeditions where they had been dropped onto rocks, or other hard surfaces and the PVC was cracked. In a couple instances, the inner epoxy core was also cracked (40' drop). They remain fully functional to this day. We wrapped some tape around the body for a little rigidity and they are often in use for various antennas. On our contest team (e.g. 6Y2A), we use the same baluns, as well as pigtails, which is the basic balun design sans the epoxy, PVC and with only a few, long beads. We toss them in the pool afterwards, which gives us a reason to finish take-down and cool off, retrieving them from the bottom of the pool. Related issue is why to use a balun? I often use RF chokes, but always use some device between the unbalanced coax feedline and the balanced dipole (singe dipole element or the feedpoint of a Yagi). The balun (B-1) is weather proof, so I prefer it over having to seal the split end of the RF choke; besides, the balun is physically much smaller on the low bands. Trivia question: What's the biggest bead balun we've ever made? Maybe I'll bring it along to the next club presentation for an item of interest. The coax in the balun is custom built. The outer conductor is 1" copper tube, 18" long. The center conductor is 1/4" copper tube with a solid aluminum rod insert. The center conductor is suspended (air dielectric) with machined rings of some type of plastic material (don't recall the type). One end has an N connector using a tapered copper fitting and there are two #10 leads on the other end. The beads are 2 1/4" OD (1 1/4" hole) and the beads can be changed in number and type. The maximum beads the body can hold is 30. With 20 beads, it weighs 7 pounds - just the ticket for an antenna on one of those excellent K-2 QRP rigs! 73, Tom, N6BT Force 12, Inc. -------------------------------------------- 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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