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I've been using two EF180BVs spaced 30' (one-eighth wavelength) and phased as my 80m low angle/directional antenna for about 4 years now. Works well for DX and contesting. Background research on radials and considering my real-estate restricted site led me to the following: - setting up (and keeping them XYL friendly) looked tough with elevated radials, so I mounted the EF180BVs on fence posts with the feedpoint about 12" above ground - current concentration is greatest near the base of the vertical. Make sure you have plenty of metal in that region. My installation has a 3 feet square piece of 12g aluminum at the base with a 1" aluminum strap to the ground side of the feedpoint. Radials are fastened with stainless steel hardware around the periphery of the plate (13 1/4" bolts per side) - long is only better if you can get lots of long radials down at your site. (See ON4UN's book) Even 1/4 wavelength is a challenge on my small lot. So I went for lots of short (20-30 foot) radials. I add to these from time to time so that I've got around 80 per element now. I used 20ga tinned copper because it was available. Ground resistance estimated at better than 3 ohms from the impedance measurements I've made. - a benefit I didn't expect came from the order in which I installed the radials. I started by laying all the radials between the pair of verticals i.e. none around the 180 degrees area on the 'outside' of the array. I found later that the performance gain from completing the full circle of radials around each vertical was slight and that the phasing circuit needed no further adjustment. This led me to conclude that a good array could be fitted into a piece of land of no more than 60 X 30 feet. I certainly had some good DX results before the outer radials were laid. This all leaves me wishing that my lot was large enough for a 4-square - has anyone tried an array of EFI80BVs or the 160m version? But at least I can put a decent signal out (and null the rest of Europe when I'm working Stateside!) 73 Dave G3WGN One of the M6T gang G5M in ARRL DX and CQWPX contests -------------------------------------------- Force12Talk mailing list provided as a service by Force 12 Antennas, Inc. Force 12 Web site: http://www.qth.com/force12 Force12Talk Message Archive: http://www.qth.com/force12/list/force12talk To unsubscribe, send a blank e-mail to force12talk-leave@qth.com For problems with the list, contact force12@qth.com |
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