Correct. They're using the 100 feet of coax to add enough loss to swamp out the native feed impedance. Note that they specify it as a minimum length, not some particular length that might provide some kind of transformation. If you use enough coax with enough loss you can get almost a perfect 50 ohm match at the transmitter with an open circuit on the far end. It becomes just a long dummy load.
KC6CNN could improve his match by simply exchanging the low loss LMR400 for RG-8X. ;) But he wouldn't get any more power to the antenna. 73, Dave AB7E On 3/11/2012 10:06 AM, Joe Subich, W4TV wrote: > The Zero-Five web site specifies 100 feet of feedline and a "wide range > antenna tuner" for that antenna. The SWR readings you report are about > what I would expect for an untuned antenna of its type. > > The Zero-Five GP40-10 is essentially a 20 meter half wave (26 feet > vertical, 8.25 feet horizontal) fed 25% from one end ... a classic > OCF design. The claims of operation on 40 (and 30 meters) bother me > since the antenna is far too short for effective 40 meter operation. > I suspect the feedline is part of the antenna on 40 meters. > > Since the antenna manufacturer specifies a minimum feedline length > of 100 feet, they're obviously using the feedline to moderate the > native feed impedance so the tuner can handle it. > > 73, > > ... Joe, W4TV > > > On 3/11/2012 11:48 AM, KC6CNN wrote: >> I installed a vertical with ground radial kit up 20 feet. >> The antenna mast and negative sheild connector is grounded to a ground rod. >> The antenna covers 10 to 40 meters. >> I can tune 10 meters fine, and fourty meters fine, but 12,15,17,20,and 30 >> will not tune and SWR are high. >> here are the SWR reading taken on AM running 25 watts. >> >> 10 meter >> >> 2804550 is 2 to 1 SWR >> >> 2882000 is 1.5 to 1 SWR >> >> >> 12 meter >> >> 2490000 is 3 to 1 SWR >> >> 24990 is 3 to 1 SWR >> >> >> 15 meter >> >> 2103900 is 4 to 1 SWR >> >> top porting is 3 to 1 SWR >> >> >> 17 meter >> >> 1809000 is 3 to 1 SWR >> >> 1817000 is 2 to 1 SWR >> >> >> 20 meter >> >> 1402800 is 2 to 1 SWR >> >> 1430000 is 2 to 1 SWR >> >> >> 30 meter >> >> 1010500 is 4 to 1 SWR >> >> 1014000 is 4 to 1 SWR >> >> >> 40 meter >> >> 7026 is 2 to 1 SWR >> >> 7290 is 1.5 to 1 SWR >> >> Any help or suggestions would be greatly appreciated. I will be receiving my >> K3 on Tuesday and am trying to get this antenna sorted out before then. >> Oh yea the rig I'm using right now is a Kenwood 570, the Coax is LMR400 with >> a 100' run. the Antenna is a ZeroFive GP10-40. >> >> Thank you >> Gerald Manthey >> KC6CNN >> >> >> -- >> View this message in context: >> http://elecraft.365791.n2.nabble.com/Strange-Vertical-need-help-tp7363205p7363205.html >> Sent from the Elecraft mailing list archive at Nabble.com. >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[email protected] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[email protected] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
