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writes: > From: "Stephen P. Hart" <k8ej@ix.netcom.com> > To: <Force12Talk@qth.com> > Subject: [Force 12 Talk] 4BA Problems > Date: Fri, 22 Dec 2000 16:20:32 -0500 > > 1.) My 4BA, mounted 12' below an EF430 (as Force 12 suggested) exhibits an > SWR of 2.3-2.6 across the 12M band. Lowest SWR (1:1) occurs at 24.275Mhz. > I have sent the complete SWR curves for all bands, as requested, to Force > 12 & Force 12 East twice, via email over the last two months. No response. > Anyone else having this SWR or lack of feedback problem? In my experience, I've had lots of 'feedback problems'. Tom is usually impossible to get ahold of. I called 5-6 times a day for a week without ever getting ahold of him and finally gave up. As far as the SWR problem, I've installed this antenna several times but don't recall any details about the SWR or if the antenna has a separate 12M feed. If it does, you adjust the driven element length. If not, sounds like you've got to play with something else. Sorry for being so vague. Since the SWR does get to just about unity at some point, you just have to change the resonance by changing the length of the appropriate DE. > The antenna does > exhibit directivity and seems to work satisfactorily. If that's the case, I wouldn't get too excited about an SWR of 2.5:1. Your rig or outboard tuner will take care of it if it's a concern but from a practical matter, an SWR of 3:1 is only about a 10% loss of power - big deal. If your rig doesn't mind, I'd use it as it. Everything else works great anyway. > > 2.) The 4BA boom has turned in the boom-to-mast clamp causing the elements > to be 5-10 degrees out of horizontal. Have talked to 4 other users (most > with C19 antennas) who have the same problem. Tightening the clamps further > doesn't seem to be a good option so pinning the boom to the mast plate > appears to be the way to go. I have concerns about weakening the boom even > drilling a small hole thru it. Any suggestions? > I've installed almost 2 dozen F12 antennas and have never run into this problem; usually it's the antenna rotating around the mast. What I found is that F12 has been using oversized nuts. Whereas they used to use 9/16" wrench sized nuts, they've been using 5/8" sized nuts which are thinner; they only have 4 threads in them where the 9/16" versions have 5 threads - 20% less thread and holding power for the 5/8" ones. Try double-nutting the U-bolts first to see if that takes care of the problem. I think that'll do it. If it doesn't, pinning the boom is about the only other solution but only do that as a last resort. Cheers, Steve K7LXC Tower Tech Champion Radio Products -------------------------------------------- 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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