On Fri, 3 Sep 2010, Kris Kirby wrote: > > Once you get it figured out, PLEASE write up an article for > > Repeater-Builder for the rest of us!! > > Make an "X" with dipole elements, and connect the feed harness to one > side, and connect the left and right sides together with > 1/4-wavelength of coax, wire, or coat-hanger. The antenna elements > should be on opposite sides of the mast. > > Something about this tells me that the stack should have the next > section up rotated 90-degrees around vertical to eliminate nulls. > > If you take that and try to build it all around the same point, it > starts looking like an imploded Lindenblad.
I could go further to say that it should be possible to do this with two DB-224 clones, the ones that hold the elements to the pipes with hose-clamps. Connect up all the feed harnesses as you normally would and connect the two by a -90 degree hybrid, or a 0-degree (in-phase) Wilkinson divider with a -90 degree section (1/4-wavelength) of coax on one leg, so that one antenna is fed -90 degrees (1/4-wavelength) from the other. Pasternak's article makes mention that these antennas are difficult to match. Things being as critical as they are, I would recommend tuning for minimum VSWR, since the receivers are hardly ever 50-ohms. This antenna may lend itself better to a split-antenna system without much separation between the circular antenna and the vertical antenna -- simply to avoid detuning the receiver duplexers if the antenna loading situation changes due to ice or other effects. -- Kris Kirby, KE4AHR Disinformation Analyst
