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the dark. But out of it I got some stacking gain on 10 and 20m. Plus, I can point to two different directions on all 3 bands and have instant switching. So, all is not bad. I just never expected that 15m would show such a negative gain. If the stack on 15 was near as good as each antenna I would have been satisfied. But, signals drop quite a bit when the 15's are phased. I sure miss my monobanders of several years ago. Life was simpler then. Maybe some day I will have time and get someone here to help me with a remote signal so I can check it out, the WX0B way. Would be interesting to see how out of phase the 15's are. I am sure that with the 15m driven element on the C3SS being fed with jumpers from the balun, compared to the C31 having no direct connection on the 15m driven element (element is shorted at its center) is causing the problem. 73 Tony N2TK -----Original Message----- From: Guy Olinger, K2AV [mailto:k2av@contesting.com] Sent: Saturday, November 16, 2002 13:06 To: n2tk@arrl.net; force12talk@qth.com Subject: Re: [Force 12 Talk] Phasing a C31XR and C3SS The reasons why the antennas may not co-phase predictably are numerous. While the physical displacement is an issue, it is not the only one. The behavior of the driver cell has to be modeled. It may deliver an EFFECTIVE phase delay caused by the interaction of the close elements. Remember you are not directly feeding the 15 meter driver, you are indirectly exciting it with the 20 meter driver, and the effective phase of the wave moving forward will be some equation of the response of both of them taken together. The general word on any attempt to phase dissimilar antennas, especially tribanders, is that it's a shot in the dark. Sometimes you can, sometimes you can't. I don't have a C3SS model up (it's linear loaded) or I could just run the numbers and tell you the phases as modeled. 73, Guy. ----- Original Message ----- From: "N2TK" <tony.kaz@verizon.net> To: <force12talk@qth.com> Sent: Saturday, November 16, 2002 10:13 AM Subject: [Force 12 Talk] Phasing a C31XR and C3SS > I have a C31XR at 82'. I have a C3SS at 41'. I have equal length Buryflex > going to both - 85'. I tried several iterations of adding coax to the C3SS > to see if I can get some gain on all 3 bands. Here is what I found out for > my situation. > - With equal length coax I did not see any stack gain on any bands. > - By adding the distance the driven elements that have the balun attached of > each antenna are from the center of the tower and multiply this by the > velocity factor of the coax, I get 62". I added a 62" piece of coax to the > C3SS. Now I see stacking gain on 10 and 20m - it varies from just noticeable > to 2 s-units. On 15m, there is negative gain when stacked- about 2-4 > s-units. > - Tried different lengths of coax added to the 62" piece. I used 4" > increments up to a total of 82". 10m and 20m still showed some gain. 15m > just got worse. It seems the best gain was with a total length of 66" of > coax added to the C3SS. It was difficult to tell the difference between 4" > either way. Did a lot of running back and forth to the tower to change coax > jumpers. > - I wonder if the reason 15m shows negative gain is because on the C31 the > feedpoint is shorted together and on the C3SS the feedpoint is joined to the > coax with jumpers? Don't know if there is an easy way to do something > different to help 15m? > - I haven't tried something less than 62". Don't know if there is a length > that would benefit 15m. > > At least I improved 10 and 20m. This will now allow me to improve my signal > on 2 bands and also allow me to have the beams in two different directions. > Even though I don't have gain on 15m, I can have the beams in two different > directions to quickly switch directions. > > Tony > N2TK > > > > > -------------------------------------------- > 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 n4zr@qth.com > > -------------------------------------------- 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 n4zr@qth.com |
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