I was asked why 90 feet of 300 ohm ladder line by the group. Ron of DX Engineering responds below.
Philip LaMarche LaMarche Enterprises, Inc. www.instantgourmetspices.com www.w9dvm.com 800-395-7795 pin 02 727-944-3226 FAX 727-937-8834 NASFT 30210 K3 #1605 CCA 98 00827 CRA 1701 W9DVM -----Original Message----- From: Rod Ehrhart [mailto:dxengineer...@dxengineering.com] Sent: Tuesday, July 14, 2009 2:46 PM To: 'Phil LaMarche' Subject: RE: [Elecraft] The use of a doublet Hello Phil, Thanks for writing. **** One of the wire antenna configurations that works best for multiple band coverage with a single wire is a ladder line fed non-resonant dipole. For impedance reasons, it is preferable to use a slightly shortened dipole instead of a resonant dipole, in relation to the lowest band of operation desired. You can operate at high power across the HF bands, if this doublet or dipole it is installed with a certain length of ladder line (not a tuned length), a high quality 1:1 current choke balun (DXE-BAL050-H10-AT), and a short run of RG-213 coax to a Wide Range Antenna Tuner with a roller inductor and large air variable capacitors. This system is described by Tom, W8JI, in DX Engineering's "Choosing the Correct Balun". The ladder line length becomes important when it is connected to a non-resonant balanced dipole being used for a wide-band or multi-band application. Using an odd multiple of an electrical, velocity factor corrected, one-eighth wavelength of feedline on the lowest frequency of operation will provide a tunable impedance at a lower SWR to the wide range tuner being used for this antenna system. For example, install an 80 through 10 meter antenna of a total length of 110 to 120 feet, with 300 ohm, 0.88 VF ladder line, with a length of around 31 or 93 or 155 feet, which represents one-, three- or five-eighths electrical wavelengths. This antenna will tune more easily on all bands, especially ALL of 80 meters! However, if one were to use 60 feet of ladder line, then high voltages could develop in the tuner, since that is an electrical one-quarter wavelength for reflected energy. This has been proven to cause difficulties in tuning and erroneous meter readings. Avoiding ladder line lengths in multiples of 1/4 wavelengths electrically is the goal. To make a great 160 through 10 meter antenna system, simply double the footage figures above. This antenna system really does work well! Try one and you will see. **** Let us know if you need any additional assistance, Phil. Thanks again and 73, Rod Ehrhart - WN8R DX Engineering Customer Support dxengineer...@dxengineering.com Orders 800-777-0703 Tech Support 330-572-3200 www.dxengineering.com -----Original Message----- From: Phil LaMarche [mailto:plama...@verizon.net] Sent: Tuesday, July 14, 2009 12:37 PM To: dxengineer...@dxengineering.com Subject: FW: [Elecraft] The use of a doublet I put this on the Elecraft reflector. Still waiting for my missing Signal Link CD. Phil Philip LaMarche LaMarche Enterprises, Inc. www.instantgourmetspices.com www.w9dvm.com 800-395-7795 pin 02 727-944-3226 FAX 727-937-8834 NASFT 30210 K3 #1605 CCA 98 00827 CRA 1701 W9DVM -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Phil LaMarche Sent: Tuesday, July 14, 2009 12:32 PM To: 'dw'; 'Elecraft_List' Subject: Re: [Elecraft] The use of a doublet DX Engineering shared an antenna with me that I put up and it works wonderful on all bands with a tuner. 120 ft and fed with 90 ft of 300 ohm line into a 1:1 balun of theirs and into the tuner with RE 213. Tuner is a Palstar AT2K. The feed line length must be 90 feet. YES, it really works. Phil Philip LaMarche LaMarche Enterprises, Inc. www.instantgourmetspices.com www.w9dvm.com 800-395-7795 pin 02 727-944-3226 FAX 727-937-8834 NASFT 30210 K3 #1605 CCA 98 00827 CRA 1701 W9DVM -----Original Message----- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of dw Sent: Tuesday, July 14, 2009 12:26 PM To: Elecraft_List Subject: [Elecraft] The use of a doublet Great post Rick! Yes, the doublet has been over the years for me the easiest and best performing all band single antenna I've ever had. I feed mine with 450 also, but the top is only 135' long. I use the more robust SGC auto-tuner in external config. 40 feet of good quality coax and a high quality balun feed the tuner. With 20 watts applied, it finds best match in 3 seconds. It makes me feel like I'm cheating!! ;^D Duane N1BBR Hello Jim, I saw two of those tape measures once and they were actually part of a military dipole antenna system. The original antenna had 2 of them and you just pulled them ou to the coresponding frequency measurements on each side and you had a resonant dipole for that frequency. So if your friend used that to measue the wire with, then its most likely somewhere around 33 feet on each side. Being fed with 300 ohm balanced feedline makes your antenna a doublet - and a doublet is a very good all band antenna ! I use a doublet here that is 178 feet long - 89 feet per side and fed with 450 ohm feedline and it works 10 thru 160 meters via the tuner. 73 - Rick McKee, KC8AON Southern Ohio - EM88sn www.angelfire.com/electronic2/qrp With God all things are possible ~ ><(('> ~ -- bw...@fastmail.net ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net 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:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
