Rick, The only problem with that is the high voltage point on a fullwave loop is electriclly opposite the feedpoint, not 1/4 wave away from the feedpoint.
It is true that opening it at the 80 meter 1/4 wave point would create an off-center fed 160 meter dipole that has been bent back on itself, but it will change the behavior on all other bands too. I still think the 160 meter trap at the 180 degree point is the best solution - or use the loop as-is and tie both sides of the feedline together and operate against ground for 160 meters. Somewhere on his website, L B Cebik simulated a 160 meter inverted L antenna with only 4 20 foot radials and it did not fare too badly - he also simulated with one 20 foot radial and that did not do badly either, so there is hope even if an extensive radial system for 160 meters is out of the question in your case. 73, Don W3FPR > -----Original Message----- > > > Dave (and Don), > > Not a silly question, Dave, what so ever. > > My suggestion was to open it up 90 degrees from the present > feed-point, 1/4 > way around...this being a voltage maximum (loop) and current > minimum (node). > > > This enables the loop to still act like a loop on 80, if you desire to > maintain it's present performance. And then on 160 it acts like, as Don > states, "a folded back 1/2 wave dipole on 160 meters" but in this case it > will be off center fed. Auto 80/160 band switching, once you get the > lengths correct for the two bands, if that is possible in this > case, as I do > not know what modes you operate. > > If you open it at, as Don suggests, 180 degrees or half way round, the 80 > meter loop turns into a bent 80 meter "2 Half-waves in Phase" with a very > high Z feed, if you maintain the feed point as is. This also shifts the > standing wave current distribution by 90 degrees, which might cause you > problems if your original antenna was set up to favor a particular area of > the world. Not convinced that is the case though, as it does > sound like you > have up 270 feet of wire in a triangular loop, "cause that's > where the trees > be". Wish I had those trees -- hi. > > 60 feet above ground is low for a horizontal 160 meter sky hook, > but you do > what'cha gotta do. > > Sounds like a fun modeling and empirical experiment to say the least. > > Regards -- Rick -- W5RH > > ------------------------------------------------- > > Dave, > > Open it at the point 180 degrees (midway around) from the feedpoint. If > your existing loop is a full wavelength on 80 meters, opening it will turn > the loop into a folded back 1/2 wave dipole on 160 meters - not as good as > straight out, but it should work since you are feeding the line > with a tuner > anyway. > In fact, you may be able to make it automatic by using a trap tuned to 160 > meters - that will electrically open the loop on 160 and only add some > inductnce on the other bands. > > 73, > Don W3FPR > > > -----Original Message----- > > > > > Not sure where you are suggesting I open it. I was considering > > disconnecting the feedline on one side where it connected to the balun. > > Is this what you mean. My apologies if it is a silly question. > > > > David Wilburn > > [EMAIL PROTECTED] > > > > > > > > Rick Hiller wrote: > > > Dave, > > > > > > Another possibility for 160 -- Don't know to what extent/effort > > you want to > > > go to get on 160, but here is an easy way, although, a bit of a > > compromise. > > > > > > Simply open the loop at one of the 80 meter voltage loops (also > > a current > > > node). The 80 meter standing wave current distribution > > /performance will > > > not change, but it will force the wire to be an off center fed 1/2 > > > wavelength for 160. Although not quite resonant within the 160 > > meter band, > > > if you feed it with open wire and run it thru the appropriate matching > > > network, you should be right. > -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.441 / Virus Database: 268.18.3/694 - Release Date: 2/20/2007 1:44 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
