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"If you have standing waves on the line, trimming the line to multiples of 1/4 wave will give resistive (zero reactance) feed points." If I am interpreting what you said correctly and if memory serves me, your statement is true if the antenna input impedance as measured at the antenna is purely resistive (but not 50 phms) to begin with. If the antenna impedance as measure at the antenna is complex then 1/4 wave lines will transform the impedance to another complex impedance (there will still be a reactive component). Adding 5 feet of coax assuming an ideal lossless transmission line would move one concentric to the center of the Smith Chart which means no change in VSWR despite the impedance as seen at the transmitter changing. A lossy 50 ohm transmission line would spiral the impedance toward the center of the chart, therefore closer to 50 ohms. But 5 feet of coax is pretty close to lossless unless the coax I used was bad which is unlikley since it was new. Still stumped. Thanks, Rick WB4EJC > -----Original Message----- > From: Barry Kirkwood [mailto:bjk@ihug.co.nz] > Sent: Sunday, June 18, 2000 5:25 PM > To: Rick Lehman; force12talk@qth.com > Subject: Re: [Force 12 Talk] !0 meter VSWR > > > If you have standing waves on the line, trimming the line to multiples of > 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 > > > -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. 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