Willis, I use two inverted vees mounted at right angles to each other for 80 and 40 meters, no interaction that way. The feedline may be of interest - it is a Transmission Line Resonator to make the 80 meter antenna broadbanded - it consists of 1 wavelength of RG-8 (that includes the balun) followed by a quarter wave of RG-11. The SWR is below 2:1 except at the very top of 75 meters. You can find the antenna in the 19th edition of the ARRL Antenna Handbook page 9-16. It works quite well for me.
I also use 2 fan dipoles - one for 30, 17, and 12 meters, and anther for 20, 15, and 10 meters. I use PVC for spreaders and keep the antenna wires separated by about 6 inches. 73, Don W3FPR On 1/1/2012 12:40 PM, WILLIS COOKE wrote: > Phil, I would put the balun at the center of the antenna and use one that > doubles as a center insulator and attach point for the raising rope. The > loss for RG-8X will be about 1 db, so you will not notice. I have had very > good luck with attaching an 80 meter dipole to the same coax and balun. I > have not tried a 30 meter, but I would expect it to work well also. I have > tried a 80-40-20 fan with no good results. I find it best to spread the 80 > and 40 at least 30 degrees and probably 90 degrees would be better. You > could use a second 75/80 dipole for either the phone or CW band or I have had > good results by putting insulators in the 80/75 and using alligator clip > leads when I want the longer antenna. The antenna coupler should not be > needed for 40 meters or for 80/75 for most of the band is you use the jumpers. > > Willis 'Cookie' Cooke > K5EWJ& Trustee N5BPS, USS Cavalla, USS Stewart > > > ________________________________ > From: Phil Hystad<phys...@mac.com> > To: d...@w3fpr.com > Cc: Elecraft List<Elecraft@mailman.qth.net> > Sent: Sunday, January 1, 2012 11:13 AM > Subject: Re: [Elecraft] Single Band 40 Meter Dipole > > Don, > > goals: > > 1. Lowest loss. > 2. Full 40-meter band coverage but resonant at 7.1 MHz. > 3. Assume using a tuner (like K3 or KAT500). > 4. Choke common mode currents. > > > Total feed line length will be on the order of 100 feet for this particular > dipole. For the 30 meter dipole I also plan to put up, total feed line > length is about 75 feet. My 80 meter dipole will be about 100 feet of > feedline. > > Before I posted this question to this forum, I would have gone ahead and used > the same configuration I used previously when I had my 80 meter doublet up. > That antenna was fed by 450 ohm ladder line to a 1:1 balun and then RG-8X to > the shack. > > But one motivation for my question is weighing the difference in loss of > tuner + 450 ohm ladder line and balun versus a direct run of RG8X right to > the feed point with a choke balun at that location. > The RG-8X loss is about 2 dB on that 100 foot run. I could switch to LMR-400 > (at 0.7 dB loss) but I am curious about other solutions. > > 73, phil, K7PEH > > > On Jan 1, 2012, at 5:39 AM, Don Wilhelm wrote: > >> Phil, >> >> What do you want to accomplish (other than just an antenna for 40 meters)? >> Lowest loss? Broadband? Easy- up? Etc? Those parameters will determine your >> best choice. >> >> Easiest IMHO is to just feed it with coax with a current mode choke at the >> feedpoint. That should present a less than 2:1 SWR over the entire 40 meter >> band. >> >> If you have an extremely long feedline (multiples of a half wave), then you >> might consider using balanced line cut to some multiple of a half wavelength >> (electrical length) and the rest of the way to the shack with coax - put the >> common mode choke at the transition between the balanced line and the coax. >> This latter suggestion takes advantage of the fact that an electrical half >> wave transmission line has the same impedance at both ends - it does not >> matter what the characteristic impedance of the line may be. >> >> But unless you have a very long distance to the antenna feedpoint, the loss >> of practical coax runs is rather low on 40 meters, so the easiest is just to >> use coax. >> >> 73, >> Don W3FPR >> >> On 1/1/2012 12:14 AM, Phil Hystad wrote: >>> OK, lots of discussion on open wire feeders and other ideas so I thought I >>> would throw out a question to soak up some of the Elecraft community >>> knowledge and wisdom. >>> >>> Given a 40-meter dipole antenna, up about 50 feet, what is the best feed >>> configuration for single band usage to minimize loss and minimize common >>> mode currents and radiation from the feed line? >>> >>> I am thinking of building such an antenna and I would have no plans for >>> using it on any other band but I would like to use it on the full spectrum >>> of 40 meters with primary focus on the low end for CW. >>> >>> My current idea is to cut the antenna for 7.1 MHz but I am not sure about >>> the best plan to feed it. I am thinking of 450 ohm window line (aka ladder >>> line) to a 1:1 balun and the coax the rest of the way into the shack. Or, >>> how about 300 ohm twin lead into a 6:1 balun with coax the rest of the way >>> into the shack? Would this be a significant difference? Or, some other >>> combination? >>> >>> Or, maybe a 1:1 balun right at the antenna feed point with coax the >>> remaining distance to the shack? >>> >>> Any comments or suggestions? >>> >>> I am thinking of also raising up two other dipoles. I have room to put up >>> 80, 40, and 30 as separate dipole antennas -- it is actually a little bit >>> more awkward to do a fan dipole so I am leaning on not doing that. >>> >>> 73, phil, K7PEH >>> > ______________________________________________________________ > 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
