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Thank you very much for your good comments. They inspired me to find out that I have perfect SWR dip at 13.450 MHz. And I did not know that one was 'allowed' to change the lenght of the T-bars. So now I want the SWR moved up - I shorten the T-bars, right? I think the effect of the tower and 4 x 6 elements 2 meters antennas are small, because turning the array does not change the SWR on the Sigma. Do you think I can conclude so from this observation? So untill further notice I conclude that I just have to shorten the T-bars. This is further supported by my QSOs during the weekend using a tuner I have SWR 1:1 and about 1000W output. From Denmark (on a hilltop) I worked on 20 meters: Brazil, Germany, Georgia, Croatia, Tanzania and Antarctica (R1ANB). So it cann't be all wrong. Vy 73 OZ1CCM Kjeld KH-Translation Gyvelbakken 11 DK-4400 Kalundborg Tel.: (+45) 45 82 96 36 Fax: (+45) 45 82 96 37 e-mail: kh@kh-translation.dk Homepage: www.kh-translation.dk PS I am told that I cannot trust an antenna analyzer as my QTH is just about 3 miles (5 km) from an AM broadcast station. Any comments? -----Original Message----- From: KEN SILVERMAN [mailto:k2kw@prodigy.net] Sent: 7. november 2003 08:32 To: Kjeld Holm; force12talk@qth.com Subject: Re: [Force 12 Talk] RE: Sigma 40XK Kjeld, It's very possible that your tower is resonant as a 1/2 wave on 20 or 1/4 wave on 40. With 7' of separation, that is about the typical distance for a 20m parasitic element. It's a bit close for 40m spacing, but there could still be strong coupling on 40m to your tower. That said, I would still think you should be able to achieve a match by adjusting the T-bars on 20. Have you done this? Adjusting the 40m coils can sometimes be very tricky - it's easy to overshoot your target frequency with small adjustments of the coil. It's quite possible that the default settings will not be valid if the antenna is strongly coupled to the tower. If you have adjusted the T-bars on 20m and still cannot get a good match, I think it lends further credibility that you are coupling to the tower. If so, the impedance of the XK on 20m is probably much lower than it's designed for. If so, you might need a hairpin across the feedpoint. That said, I have installed a number of 2 ele Sigma verticals, and we do not need a hair pin. If you cannot get a good match, I would suggest moving the vertical as far from the tower as possible. But I assume you have already considered that, and it's not possible. 73, Kenny K2KW Team Vertical ----- Original Message ----- From: "Kjeld Holm" <kh@kh-translation.dk> To: <force12talk@qth.com> Sent: Friday, November 07, 2003 11:06 AM Subject: [Force 12 Talk] RE: Sigma 40XK > Hello All, > > I just installed the Sigma 40XK on a wooden structure on my lawn close to a > brick house and with the lower T-bar 7 feet (2 meter) up for the purpose of > been able to walk on the lawn below it. The antenna is also just about 7 > feet from a 18 feet tower (metal) with 4 x 6 elm for 2 meters. > > On 20 meters I have SWR 1:2.5 at the bottom of the band slowly rising to > 1:2.8 at the upper band limit. Is this what I have to expect being so close > to other structures? Or do you have any suggestions? > > On 40 meters I spend some time fidling wiht the coils but could not get any > resonable results that's why I resort to 20 meters. > > PS The manual says SWR 1:1.3 for 20 meters. > > Vy 73 > OZ1CCM Kjeld > > > > > -------------------------------------------- > 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 > -------------------------------------------- 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 -------------------------------------------- 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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