Mike, I recently put up a 240ft doublet fed with 600 ohm open wire feeder. The feedline is "about" 200 ft long. It terminates in the Elecraft BL2 balun set for 4:1 and it tunes all bands 160-6M on the K3.
73 Greg AB7R -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Mike Scott Sent: Tuesday, March 11, 2008 7:55 PM To: elecraft@mailman.qth.net Subject: [Elecraft] K3 Multi-Band antenna thoughts I am considering building a multi-band doublet fed with ladder line to the window and then 10-12 feet of coax to the K3 from the window interface. I would let the K3 ATU tune the beast. I have been playing with a coax calculator and with low loss coax and 10:1 SWR the losses in the short run of coax up to 30MHz are manageable to ½ dB. The ladder line can handle the mismatch with small losses. I was thinking of putting a sleeve balun at the window interface from the coax to ladder line. I could of course put two different length doublets in parallel at the feed point if that would tame problem bands. I dont need this antenna to go to 50 MHz as I will have a separate antenna for 6M. I dont have antenna modeling software. I know I will have pattern issues if I try to push a long antenna too high in frequency. I am not thinking right now of pushing this antenna to 160M. So now the questions: 1. Is there a magic doublet antenna length that will end up with less than 10:1 SWR on the most bands? I know Cebik likes 88 feet or 44 feet depending on lowest operating band but I dont know that he has solved my exact problem for 10:1 SWR or less on all bands. 2. Is there a magic feed line length to make this all work? 3. Have any of you tried something similar to this with the K3 ATU? I have read the reports of just tuning up any old antenna that you have and you get it to work at some unknown efficiency. I have done this too. I know it is time for me to bite the bullet and purchase some real antennal modeling tools. Mike Scott AE6WA Tarzana, CA K3/100 SN508 _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com No virus found in this incoming message. Checked by AVG. Version: 7.5.518 / Virus Database: 269.21.7/1325 - Release Date: 3/11/2008 1:41 PM No virus found in this outgoing message. Checked by AVG. Version: 7.5.518 / Virus Database: 269.21.7/1325 - Release Date: 3/11/2008 1:41 PM _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
