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Re: [TowerTalk] Beta match adds capacitive reactance on 2 el Hy-gain 40m

 Subject: Re: [TowerTalk] Beta match adds capacitive reactance on 2 el Hy-gain 40m ? Steve Hunt Wed, 24 Oct 2012 14:47:10 +0100 mailto:towertalk@contesting.com>
 To transform 22-j25 close to 50 Ohms you need a shunt reactance of +j44 To transform 17-j24 close to 50 Ohms you need a shunt reactance of +j36 Hope that helps 73, Steve G3TXQ On 24/10/2012 10:21, DX Supply AB wrote: Hello!! Has anyone an answer to this Beta Match behavior on a 2 el linear loaded Hy-gain DIS 7-2? I have assembled the antenna again after some years in the garage. I designed it for SWR min at 7040 kHz and measured up the Feed point impedance at 30 feet to Z=17 --j24 after having shortened the driver a little more ( about 1 ½ ") than what is said in the manual. In line with theory for a linear loaded design. Increasing height to 60 feet I assume change (according to Cebik) the Z to about 22 --j25 or so. Not much change. According to theory (and W4RNL Cebiks excellent paper on web) the only thing now needed to tune out the capacitive reactance of --j24 is to add an inductance of about 33 ohms. This can be done with a Beta match and I started using the Hy.gain Beta match supplied with the antenna (1/4" x 72 " rods spaced 2,4 " from the boom). This way final impedance ens up close to 50 ohms which is good. However, inserting the Beta match worsened the Z to 32,5-42 that is adding both resistance and capacitive reactance to the feed point impedance. How an earth can the reactance be more capacitive with an inductive Beta match over the feed point? Is the best thing to throw the beta match over board an build a small inductor coil of 33 ohms? Thanking in advance, Kari SM0HRP _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesting.com/mailman/listinfo/towertalk
 Current Thread [TowerTalk] Beta match adds capacitive reactance on 2 el Hy-gain 40m ?, DX Supply AB Re: [TowerTalk] Beta match adds capacitive reactance on 2 el Hy-gain 40m ?, Steve Hunt <= Re: [TowerTalk] Beta match adds capacitive reactance on 2 el Hy-gain 40m ?, RMorris