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thanks for reply. This antenna was 9 meters above flat concrete roof of a 7 storey hotel. On a steel mast. Higher than that was not considered required to work properly. However, there is one thing that we never managed, and that was discovered from N4ZR reply: - tweaking 40m coil! We just put it up, and did not tweak it to find better resonance. The other thing is proximity of steel guywires that were going all the way up to the antenna. Third thing is that the owner of the antenna did not apply any conductive antioxidant grease. I guess, there will be better luck in assembling it next time, 40feet above the cliff on the beach, with tweaking exercie and nonconductive ropes as guys... 73 Kele -----Original Message----- From: Natan Huffman <force12e@lightlink.com> To: F12Reflector <force12talk@qth.com>; kk <kk@cg.yu> Date: èetvrtak, 09.03.2000. 17:06 Subject: Re: [Force 12 Talk] re C4S >Kele, > >Expecting a 40 meter antenna to "work" when mounted directly above and at >low heights above a metal or concrete (probably with reinforcing rod) roof >is an unreasonable expectation. The dealer, exhibiting a knowledge of >antenna theory and application, was indeed correct. I would expect the >impedance to be much different than the needed 50 ohms and the pattern would >also vary dramatically from what is expected. Furthermore, how do you know >the antenna didn't work? The antenna could have been "working" but showing >a high VSWR due to the mis-match caused by the roof. Since you spend much >time modeling, I would think you could recreate just what is happening with >an antenna's impedance mounted at very low lambdas above a metal >counterpoise. > >The logic behind the dealers recommendation is sound as well as the design >of the antenna. The logic behind your installation and expectations escapes >me! > >Natan W6XR/2 >FORCE 12 East >Ithaca, NY > >----- Original Message ----- >From: kk <kk@cg.yu> >To: Alex (Tex) Ihasz <vk1tx@one.net.au>; Force 12 Reflector ><Force12Talk@qth.com> >Sent: Wednesday, March 08, 2000 9:36 AM >Subject: Re: [Force 12 Talk] re C4S > > >> C4SXL did not want to tune on 40m, while on contespedition in Cyprus. The >> contest ended with inverted V for 40m band. However, P3A team used C4XL >with >> satisfactory results. European dealer suggested we do not put the antenna >> above metallic or concrete roof. Well, we questioned this logic, since >flat >> hotel roof was ideal for this antenna... Everything was double checked, >> separate feedline as required, but still no SWR dip less than 3:1. >> >> 73 Kele >> 5B4/4O6A >> >> -----Original Message----- >> From: Alex (Tex) Ihasz <vk1tx@one.net.au> >> To: Force 12 Reflector <Force12Talk@qth.com> >> Date: srijeda, 08.03.2000. 11:59 >> Subject: [Force 12 Talk] re C4S >> >> >> >Hi All, >> >Will be purchasing a Force 12 C4s Yagi at Dayton this year. >> >Can anyone give some information re the performance on 40m and any >> >problems with the 2 feed line system of the yagi? >> >Tower height is only 55ft. >> >Cheers, >> >TEX VK1TX >> >email: vk1tx@one.one.net.au >> > >> > >> > >> > >> >-------------------------------------------- >> >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 force12@qth.com >> > >> > >> > >> >> >> -------------------------------------------- >> 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 force12@qth.com >> >> > > -------------------------------------------- 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 force12@qth.com |
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