*note1: “40m tail” implies both 40m and 30m links are attached, other settings are for the 20m\/10m as 20m efhw or 30m\/15m as 30m efhw.<\/em><\/p>\r\n note2: The transformer taps are numbered 1-5, where tap 1=4.5:1, 2=5.5:1, 3=6.5:1, 4=7.5:1, and tap 5=8.5:1 turns ratios.\u00c2\u00a0 corresponding impedance values would be 1013, 1513, 2113, 2813, and 3613 ohms.<\/em><\/p>\r\n note3: -right click and “view image” to see full size images below For the 10m images above, on the left is the modeled current and radiation patterns for the 40m EFHW when used on 10m.\u00c2\u00a0 The right is the current and radiation pattern for the 20m EFHW used on 10m.\u00c2\u00a0 Switching requires lowering the antenna to either detach or reattach the link at 20m.<\/p>\r\n Given the lengths of the wire using a 30 foot(~9 meter) support, either configuration will have a considerable vertical component.\u00c2\u00a0 The 40m version will add a substantial horizontal component.\u00c2\u00a0 The vertical components will mimic the horizontal patterns to some extent.\u00c2\u00a0 But the patterns will likely favor different directions.\u00c2\u00a0 The differences will surely be modest – maybe enough to be worth testing as options.\u00c2\u00a0 If nothing else, it may help reduce QRN in some circumstances.<\/p>\r\n For 20m, the radiation patterns might actually be more interesting.\u00c2\u00a0 The full wave version(from 40m configuration) will present a compressed combination of horizontal and vertical components.\u00c2\u00a0 The half wave version(20m) configured with most of the antenna vertical will have a mostly vertical component with the 30ft\/9m support.\u00c2\u00a0 This may be a fun experiment in a field day operation.\u00c2\u00a0 maybe worth the effort of switching the links<\/p>\r\n
<\/em><\/p>\r\nModel Radiation patterns-10m<\/h5>\r\n
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Radiation patterns-20m<\/h5>\r\n
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Addendums<\/h5>\r\n