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In article , Michael Melland
wrote: Looking for opinions..... seems conventional wisdom indicates a discone. There are active antennas covering this range too. Any opinions or recommendations ? Mike Depends on what you're listning to-- You can get a log-periodic to cover that range (Create makes one). You can go the discone route. The LP has gain, and needs to be pointed. The discone doesn't exhibit gain (over isotropic), and the radiation pattern changes with frequency. In particular, the take-off angle increases with frequency. If you have 25 MHz as your low point, by the time you get to 440, the main lobe is going to be around 50 degrees. Oh, and the discone, along with ground-plane antennas, has a pretty good null directly vertical from the antenna. Makes it kind of a pain for satellite work, when your antenna has a sharp null when the bird is directly overhead! For info on discones, see for example, the RSGB VHF/UHF manual. Discones are covered in section 8.37, and log periodics are in section 8.21. The RSGB book gives a lucid explanation of construction if you want to roll your own, and for 440 MHz and up, that's pretty easy and pretty small. I use a pair of discones, one for the lower end of things (50-250 MHz or so), and a second for the higher end (440-1300 MHz). I also have an eggbeater (from m2) for 137 and 144 MHz birds. And don't skimp on the feedline -- LM400 is a good starting point. -- Namaste- |
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