A Butternut, like the HF-9 or HF-6 are great performing antennas... BUT they require resonant radials when installed above ground level...like on your roof. An antenna like this will normally run circles, performance wise, around the ground independant types...like the Cushcraft R7, R8, or R7000. The ground independant designs are sometimes called half wave verticals, but in reality they are off-center fed, vertically mounted, trapped dipoles. There are too many many compromises built into these antennas for the sake of convenience to allow them to be highly efficient radiators. They are however very easy to erect and install and normally give you a number of bands. The trade-off is yours to make. What is most important to you, ease of installation or squeezing out the last bit of performance? If you decide to go the Butternut or Hustler route, normally a couple of quarter wave radials for each band you want operate is sufficient, IF the antenna is roof mounted. Many more would be needed on a ground mounted installation, but they would not necessarily need to be resonant then. For a definitve discussion of radials, check out:http://www.bencher.com/pdf_download.html
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All verticals are NOT created equal!