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supposed to be removed from the antenna feed point and placed between the relay box and balun/RF choke. Thanks Natan Yesterday the hairpin coil was moved and adjusted for lowest SWR. In the shack these are the readings from an MFJ 269 antenna analyzer: Relay Lowest SWR Frequency Open 1.7 6.870 Closed 1.65 7.080 It is obvious that the resonant frequency of the 40-meter driven element was reduced significantly by insertion of the relay box. Thus the shorting bar must now be moved again to raise resonance to 7.220 with relay contacts closed. If the difference between closed and open remains at 210 KHz, then CW should be resonant at 7.010 after the final adjustment. Two articles that have helped to understand what is going on during the tuning process are available at the Force 12 web site. For novice tuners like myself, save yourself a lot of grief by reading these BEFORE climbing the tower. Tuning help: http://force12inc.com/F12-SE-Yagi-tuning-Elev-Radials-1-2.htm Debugging help: http://force12inc.com/debug-index.htm Happy tuning. Keith WD5DXL -----Original Message----- From: Keith Dutson [mailto:kjdutson@earthlink.net] Sent: Sunday, August 03, 2003 11:30 PM To: Force12Talk Subject: RE: [Force 12 Talk] C-4XL Tuning Question [snip] I could not reach far enough to access the far end of the shorting bars and didn't feel like rotating the antenna down by myself, so only the near end shorting bars were adjusted as far as possible toward the element tip. This resulted in resonance at about 7.210 MHz with relay on and 7.140 MHz with it off. Unfortunately the VSWR is very high in both cases: about 3.1 and 4.0 respectively. This is the lowest reading obtained by adjusting both hairpin coils (original at antenna and new at relay box balun connection). Now I am wondering if this problem is caused by adjusting only one side of the shorting bars, or perhaps the hairpin on the driven element should be removed, leaving only the smaller hairpin on the balun side of the relay box. Any ideas? Thanks. Keith [snip] -------------------------------------------- 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 force12@qth.com |
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