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1/4 wave will give resistive (zero reactance) feed points. From your report it appears that you have standing waves and were trying to match to a line which was close to a multiple of 1/2 wave. Adding 5ft (approx 1/4 wave taking velocity factor into account) gave you low swr. cheers es 73 Barry Kirkwood PhD ZL1DD Signal Hill Homestay B&B 66 Cory Road Palm Beach Waiheke Island 1240 NEW ZEALAND www.waiheke.co.nz/signal.htm ----- Original Message ----- From: Rick Lehman <rlehman@gate.net> To: <force12talk@qth.com> Sent: Sunday, 18 June, 2000 11:11 PM Subject: RE: [Force 12 Talk] !0 meter VSWR > I have a C19XR with a high VSWR (when measured at the transmitter end of the > coax) on 10 meters and do not use an LP filter. It was suggested by force > 12 that I add about 5 feet of coax. I did that and to my amazement it > worked. I have been trying to understand why this would work and have not > yet come up with a technical explanation (Force 12 cannot explain it > either). With an ideal line, the length of coax should not make a > difference on the VSWR seen at the transmitter. It instead would only > affect the phase angle from a Smith Chart standpoint. From a real world > lossy line standpoint, 5 feet of coax is not long enough to cause any > appreciable loss or effect on the VSWR. My first thought was that the force > 12 balun was bad as the symptoms suggest that the coax was functioning as > part of the antenna. However, I removed the 5 feet of coax, and replaced > the balun with a current balun from Hygain. The results were the same as > with the force 12 balun... Therefore I have ruled out this possibility. My > coax is new, so I am for the time being ruling out this possibility. The > antenna seems to work fine on 10 meters, but I am bothered that I do not > understand this phenomena. Any ideas? > > Rick WB4EJC > Coconut Creek, Florida > > > -----Original Message----- > > From: Tony [mailto:ad6id@arrl.net] > > Sent: Saturday, June 17, 2000 4:47 PM > > To: force12talk@qth.com > > Subject: Re: [Force 12 Talk] !0 meter VSWR > > > > > > At 01:37 PM 6/17/00 -0400, Natan Huffman wrote: > > ...> > > >Five out of five installations experiencing this high 10 meter > > VSWR problem > > >fixed the problem by removing the LP filter! All of the problem filters > > >were of the same manufacturer. > > > > > >So, if you don't think things are quite right on 10 meters, look > > at your use > > >of a LP filter as a very possible problem initiator. > > > > Thanks for the great detective work. Could you tell us which > > 'same manufacturer? > > Or do you suspect that they all have this effect? > > > > I didn't catch which antenna. I have a C4SXL (without a LP > > filter, so far). > > > > 73, Tony > > > > Tony Armendariz, AD6ID > > ad6id@arrl.net > > FISTS 3535 WPSS ARRL > > > > > > -------------------------------------------- > > 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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